Merge branch 'release-4-5-patches' into release-4-6
[alexxy/gromacs.git] / src / mdlib / pme.c
index 2f5ce0a84bdb02f730a76a55205029b73fd9a8a3..8342621cad818ecbe0e5fd396580cdf47e2656fa 100644 (file)
@@ -1,12 +1,12 @@
 /* -*- mode: c; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; c-file-style: "stroustrup"; -*-
  *
- * 
+ *
  *                This source code is part of
- * 
+ *
  *                 G   R   O   M   A   C   S
- * 
+ *
  *          GROningen MAchine for Chemical Simulations
- * 
+ *
  *                        VERSION 3.2.0
  * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
  * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version 2
  * of the License, or (at your option) any later version.
- * 
+ *
  * If you want to redistribute modifications, please consider that
  * scientific software is very special. Version control is crucial -
  * bugs must be traceable. We will be happy to consider code for
  * inclusion in the official distribution, but derived work must not
  * be called official GROMACS. Details are found in the README & COPYING
  * files - if they are missing, get the official version at www.gromacs.org.
- * 
+ *
  * To help us fund GROMACS development, we humbly ask that you cite
  * the papers on the package - you can find them in the top README file.
- * 
+ *
  * For more info, check our website at http://www.gromacs.org
- * 
+ *
  * And Hey:
  * GROwing Monsters And Cloning Shrimps
  */
@@ -54,7 +54,7 @@
  *
  * It might seem an overkill, but better safe than sorry.
  * /Erik 001109
- */ 
+ */
 
 #ifdef HAVE_CONFIG_H
 #include <config.h>
 #ifdef GMX_LIB_MPI
 #include <mpi.h>
 #endif
-#ifdef GMX_THREADS
+#ifdef GMX_THREAD_MPI
 #include "tmpi.h"
 #endif
 
-
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
+#include <assert.h>
 #include "typedefs.h"
 #include "txtdump.h"
 #include "vec.h"
 #include "gmx_wallcycle.h"
 #include "gmx_parallel_3dfft.h"
 #include "pdbio.h"
+#include "gmx_cyclecounter.h"
+
+/* Single precision, with SSE2 or higher available */
+#if defined(GMX_X86_SSE2) && !defined(GMX_DOUBLE)
+
+#include "gmx_x86_sse2.h"
+#include "gmx_math_x86_sse2_single.h"
 
-#if ( !defined(GMX_DOUBLE) && ( defined(GMX_IA32_SSE) || defined(GMX_X86_64_SSE) || defined(GMX_X86_64_SSE2) ) )
-#include "gmx_sse2_single.h"
+#define PME_SSE
+/* Some old AMD processors could have problems with unaligned loads+stores */
+#ifndef GMX_FAHCORE
+#define PME_SSE_UNALIGNED
+#endif
 #endif
 
 #include "mpelogging.h"
 /* #define TAKETIME (step > 1 && timesteps < 10) */
 #define TAKETIME FALSE
 
+/* #define PME_TIME_THREADS */
+
 #ifdef GMX_DOUBLE
 #define mpi_type MPI_DOUBLE
 #else
 #define mpi_type MPI_FLOAT
 #endif
 
+/* GMX_CACHE_SEP should be a multiple of 16 to preserve alignment */
+#define GMX_CACHE_SEP 64
+
+/* We only define a maximum to be able to use local arrays without allocation.
+ * An order larger than 12 should never be needed, even for test cases.
+ * If needed it can be changed here.
+ */
+#define PME_ORDER_MAX 12
+
 /* Internal datastructures */
 typedef struct {
     int send_index0;
@@ -124,8 +145,23 @@ typedef struct {
     int  noverlap_nodes;
     int  *send_id,*recv_id;
     pme_grid_comm_t *comm_data;
+    real *sendbuf;
+    real *recvbuf;
 } pme_overlap_t;
 
+typedef struct {
+    int *n;     /* Cumulative counts of the number of particles per thread */
+    int nalloc; /* Allocation size of i */
+    int *i;     /* Particle indices ordered on thread index (n) */
+} thread_plist_t;
+
+typedef struct {
+    int  n;
+    int  *ind;
+    splinevec theta;
+    splinevec dtheta;
+} splinedata_t;
+
 typedef struct {
     int  dimind;            /* The index of the dimension, 0=x, 1=y */
     int  nslab;
@@ -144,6 +180,7 @@ typedef struct {
     int  pd_nalloc;
     int  *pd;
     int  *count;            /* The number of atoms to send to each node */
+    int  **count_thread;
     int  *rcount;           /* The number of atoms to receive */
 
     int  n;
@@ -151,15 +188,65 @@ typedef struct {
     rvec *x;
     real *q;
     rvec *f;
-    gmx_bool bSpread;           /* These coordinates are used for spreading */
+    gmx_bool bSpread;       /* These coordinates are used for spreading */
     int  pme_order;
-    splinevec theta,dtheta;
     ivec *idx;
     rvec *fractx;            /* Fractional coordinate relative to the
-                              * lower cell boundary 
+                              * lower cell boundary
                               */
+    int  nthread;
+    int  *thread_idx;        /* Which thread should spread which charge */
+    thread_plist_t *thread_plist;
+    splinedata_t *spline;
 } pme_atomcomm_t;
 
+#define FLBS  3
+#define FLBSZ 4
+
+typedef struct {
+    ivec ci;     /* The spatial location of this grid       */
+    ivec n;      /* The size of *grid, including order-1    */
+    ivec offset; /* The grid offset from the full node grid */
+    int  order;  /* PME spreading order                     */
+    real *grid;  /* The grid local thread, size n           */
+} pmegrid_t;
+
+typedef struct {
+    pmegrid_t grid;     /* The full node grid (non thread-local)            */
+    int  nthread;       /* The number of threads operating on this grid     */
+    ivec nc;            /* The local spatial decomposition over the threads */
+    pmegrid_t *grid_th; /* Array of grids for each thread                   */
+    int  **g2t;         /* The grid to thread index                         */
+    ivec nthread_comm;  /* The number of threads to communicate with        */
+} pmegrids_t;
+
+
+typedef struct {
+#ifdef PME_SSE
+    /* Masks for SSE aligned spreading and gathering */
+    __m128 mask_SSE0[6],mask_SSE1[6];
+#else
+    int dummy; /* C89 requires that struct has at least one member */
+#endif
+} pme_spline_work_t;
+
+typedef struct {
+    /* work data for solve_pme */
+    int      nalloc;
+    real *   mhx;
+    real *   mhy;
+    real *   mhz;
+    real *   m2;
+    real *   denom;
+    real *   tmp1_alloc;
+    real *   tmp1;
+    real *   eterm;
+    real *   m2inv;
+
+    real     energy;
+    matrix   vir;
+} pme_work_t;
+
 typedef struct gmx_pme {
     int  ndecompdim;         /* The number of decomposition dimensions */
     int  nodeid;             /* Our nodeid in mpi->mpi_comm */
@@ -175,76 +262,77 @@ typedef struct gmx_pme {
     MPI_Datatype  rvec_mpi;  /* the pme vector's MPI type */
 #endif
 
-    gmx_bool bPPnode;            /* Node also does particle-particle forces */
-    gmx_bool bFEP;               /* Compute Free energy contribution */
+    int  nthread;            /* The number of threads doing PME */
+
+    gmx_bool bPPnode;        /* Node also does particle-particle forces */
+    gmx_bool bFEP;           /* Compute Free energy contribution */
     int nkx,nky,nkz;         /* Grid dimensions */
+    gmx_bool bP3M;           /* Do P3M: optimize the influence function */
     int pme_order;
-    real epsilon_r;           
-    
-    real *  pmegridA;  /* Grids on which we do spreading/interpolation, includes overlap */
-    real *  pmegridB;
+    real epsilon_r;
+
+    pmegrids_t pmegridA;  /* Grids on which we do spreading/interpolation, includes overlap */
+    pmegrids_t pmegridB;
+    /* The PME charge spreading grid sizes/strides, includes pme_order-1 */
     int     pmegrid_nx,pmegrid_ny,pmegrid_nz;
-    int     pmegrid_start_ix,pmegrid_start_iy,pmegrid_start_iz;    
-    
-    real *  pmegrid_sendbuf;
-    real *  pmegrid_recvbuf;
-    
+    /* pmegrid_nz might be larger than strictly necessary to ensure
+     * memory alignment, pmegrid_nz_base gives the real base size.
+     */
+    int     pmegrid_nz_base;
+    /* The local PME grid starting indices */
+    int     pmegrid_start_ix,pmegrid_start_iy,pmegrid_start_iz;
+
+    /* Work data for spreading and gathering */
+    pme_spline_work_t *spline_work;
+
     real *fftgridA;             /* Grids for FFT. With 1D FFT decomposition this can be a pointer */
     real *fftgridB;             /* inside the interpolation grid, but separate for 2D PME decomp. */
     int   fftgrid_nx,fftgrid_ny,fftgrid_nz;
-    
+
     t_complex *cfftgridA;             /* Grids for complex FFT data */
-    t_complex *cfftgridB;            
+    t_complex *cfftgridB;
     int   cfftgrid_nx,cfftgrid_ny,cfftgrid_nz;
-    
+
     gmx_parallel_3dfft_t  pfft_setupA;
     gmx_parallel_3dfft_t  pfft_setupB;
-    
+
     int  *nnx,*nny,*nnz;
     real *fshx,*fshy,*fshz;
-    
+
     pme_atomcomm_t atc[2];  /* Indexed on decomposition index */
     matrix    recipbox;
     splinevec bsp_mod;
-    
-    pme_overlap_t overlap[2]; /* Indexed on dimension, 0=x, 1=y */
 
+    pme_overlap_t overlap[2]; /* Indexed on dimension, 0=x, 1=y */
 
     pme_atomcomm_t atc_energy; /* Only for gmx_pme_calc_energy */
-    
+
     rvec *bufv;             /* Communication buffer */
     real *bufr;             /* Communication buffer */
     int  buf_nalloc;        /* The communication buffer size */
 
-    /* work data for solve_pme */
-    int      work_nalloc;
-    real *   work_mhx;
-    real *   work_mhy;
-    real *   work_mhz;
-    real *   work_m2;
-    real *   work_denom;
-    real *   work_tmp1_alloc;
-    real *   work_tmp1;
-    real *   work_m2inv;
+    /* thread local work data for solve_pme */
+    pme_work_t *work;
 
     /* Work data for PME_redist */
-    gmx_bool     redist_init;
-    int *    scounts; 
+    gmx_bool redist_init;
+    int *    scounts;
     int *    rcounts;
     int *    sdispls;
     int *    rdispls;
     int *    sidx;
-    int *    idxa;    
+    int *    idxa;
     real *   redist_buf;
     int      redist_buf_nalloc;
-    
+
     /* Work data for sum_qgrid */
     real *   sum_qgrid_tmp;
     real *   sum_qgrid_dd_tmp;
 } t_gmx_pme;
 
 
-static void calc_interpolation_idx(gmx_pme_t pme,pme_atomcomm_t *atc)
+static void calc_interpolation_idx(gmx_pme_t pme,pme_atomcomm_t *atc,
+                                   int start,int end,int thread)
 {
     int  i;
     int  *idxptr,tix,tiy,tiz;
@@ -252,42 +340,65 @@ static void calc_interpolation_idx(gmx_pme_t pme,pme_atomcomm_t *atc)
     real rxx,ryx,ryy,rzx,rzy,rzz;
     int  nx,ny,nz;
     int  start_ix,start_iy,start_iz;
-    
+    int  *g2tx,*g2ty,*g2tz;
+    gmx_bool bThreads;
+    int  *thread_idx=NULL;
+    thread_plist_t *tpl=NULL;
+    int  *tpl_n=NULL;
+    int  thread_i;
+
     nx  = pme->nkx;
     ny  = pme->nky;
     nz  = pme->nkz;
-    
+
     start_ix = pme->pmegrid_start_ix;
     start_iy = pme->pmegrid_start_iy;
     start_iz = pme->pmegrid_start_iz;
-    
+
     rxx = pme->recipbox[XX][XX];
     ryx = pme->recipbox[YY][XX];
     ryy = pme->recipbox[YY][YY];
     rzx = pme->recipbox[ZZ][XX];
     rzy = pme->recipbox[ZZ][YY];
     rzz = pme->recipbox[ZZ][ZZ];
-    
-    for(i=0; (i<atc->n); i++) {
+
+    g2tx = pme->pmegridA.g2t[XX];
+    g2ty = pme->pmegridA.g2t[YY];
+    g2tz = pme->pmegridA.g2t[ZZ];
+
+    bThreads = (atc->nthread > 1);
+    if (bThreads)
+    {
+        thread_idx = atc->thread_idx;
+
+        tpl   = &atc->thread_plist[thread];
+        tpl_n = tpl->n;
+        for(i=0; i<atc->nthread; i++)
+        {
+            tpl_n[i] = 0;
+        }
+    }
+
+    for(i=start; i<end; i++) {
         xptr   = atc->x[i];
         idxptr = atc->idx[i];
         fptr   = atc->fractx[i];
-        
+
         /* Fractional coordinates along box vectors, add 2.0 to make 100% sure we are positive for triclinic boxes */
         tx = nx * ( xptr[XX] * rxx + xptr[YY] * ryx + xptr[ZZ] * rzx + 2.0 );
         ty = ny * (                  xptr[YY] * ryy + xptr[ZZ] * rzy + 2.0 );
         tz = nz * (                                   xptr[ZZ] * rzz + 2.0 );
-        
+
         tix = (int)(tx);
         tiy = (int)(ty);
         tiz = (int)(tz);
-        
+
         /* Because decomposition only occurs in x and y,
          * we never have a fraction correction in z.
          */
         fptr[XX] = tx - tix + pme->fshx[tix];
         fptr[YY] = ty - tiy + pme->fshy[tiy];
-        fptr[ZZ] = tz - tiz;   
+        fptr[ZZ] = tz - tiz;
 
         idxptr[XX] = pme->nnx[tix];
         idxptr[YY] = pme->nny[tiy];
@@ -298,40 +409,109 @@ static void calc_interpolation_idx(gmx_pme_t pme,pme_atomcomm_t *atc)
         range_check(idxptr[YY],0,pme->pmegrid_ny);
         range_check(idxptr[ZZ],0,pme->pmegrid_nz);
 #endif
-  }  
+
+        if (bThreads)
+        {
+            thread_i = g2tx[idxptr[XX]] + g2ty[idxptr[YY]] + g2tz[idxptr[ZZ]];
+            thread_idx[i] = thread_i;
+            tpl_n[thread_i]++;
+        }
+    }
+
+    if (bThreads)
+    {
+        /* Make a list of particle indices sorted on thread */
+
+        /* Get the cumulative count */
+        for(i=1; i<atc->nthread; i++)
+        {
+            tpl_n[i] += tpl_n[i-1];
+        }
+        /* The current implementation distributes particles equally
+         * over the threads, so we could actually allocate for that
+         * in pme_realloc_atomcomm_things.
+         */
+        if (tpl_n[atc->nthread-1] > tpl->nalloc)
+        {
+            tpl->nalloc = over_alloc_large(tpl_n[atc->nthread-1]);
+            srenew(tpl->i,tpl->nalloc);
+        }
+        /* Set tpl_n to the cumulative start */
+        for(i=atc->nthread-1; i>=1; i--)
+        {
+            tpl_n[i] = tpl_n[i-1];
+        }
+        tpl_n[0] = 0;
+
+        /* Fill our thread local array with indices sorted on thread */
+        for(i=start; i<end; i++)
+        {
+            tpl->i[tpl_n[atc->thread_idx[i]]++] = i;
+        }
+        /* Now tpl_n contains the cummulative count again */
+    }
+}
+
+static void make_thread_local_ind(pme_atomcomm_t *atc,
+                                  int thread,splinedata_t *spline)
+{
+    int  n,t,i,start,end;
+    thread_plist_t *tpl;
+
+    /* Combine the indices made by each thread into one index */
+
+    n = 0;
+    start = 0;
+    for(t=0; t<atc->nthread; t++)
+    {
+        tpl = &atc->thread_plist[t];
+        /* Copy our part (start - end) from the list of thread t */
+        if (thread > 0)
+        {
+            start = tpl->n[thread-1];
+        }
+        end = tpl->n[thread];
+        for(i=start; i<end; i++)
+        {
+            spline->ind[n++] = tpl->i[i];
+        }
+    }
+
+    spline->n = n;
 }
 
-static void pme_calc_pidx(int natoms, matrix recipbox, rvec x[],
-                          pme_atomcomm_t *atc)
+
+static void pme_calc_pidx(int start, int end,
+                          matrix recipbox, rvec x[],
+                          pme_atomcomm_t *atc, int *count)
 {
     int  nslab,i;
     int  si;
     real *xptr,s;
     real rxx,ryx,rzx,ryy,rzy;
-    int *pd,*count;
+    int *pd;
 
     /* Calculate PME task index (pidx) for each grid index.
      * Here we always assign equally sized slabs to each node
      * for load balancing reasons (the PME grid spacing is not used).
      */
-    
+
     nslab = atc->nslab;
     pd    = atc->pd;
-    count = atc->count;
 
     /* Reset the count */
     for(i=0; i<nslab; i++)
     {
         count[i] = 0;
     }
-    
+
     if (atc->dimind == 0)
     {
         rxx = recipbox[XX][XX];
         ryx = recipbox[YY][XX];
         rzx = recipbox[ZZ][XX];
         /* Calculate the node index in x-dimension */
-        for(i=0; (i<natoms); i++)
+        for(i=start; i<end; i++)
         {
             xptr   = x[i];
             /* Fractional coordinates along box vectors */
@@ -346,7 +526,7 @@ static void pme_calc_pidx(int natoms, matrix recipbox, rvec x[],
         ryy = recipbox[YY][YY];
         rzy = recipbox[ZZ][YY];
         /* Calculate the node index in y-dimension */
-        for(i=0; (i<natoms); i++)
+        for(i=start; i<end; i++)
         {
             xptr   = x[i];
             /* Fractional coordinates along box vectors */
@@ -358,10 +538,53 @@ static void pme_calc_pidx(int natoms, matrix recipbox, rvec x[],
     }
 }
 
+static void pme_calc_pidx_wrapper(int natoms, matrix recipbox, rvec x[],
+                                  pme_atomcomm_t *atc)
+{
+    int nthread,thread,slab;
+
+    nthread = atc->nthread;
+
+#pragma omp parallel for num_threads(nthread) schedule(static)
+    for(thread=0; thread<nthread; thread++)
+    {
+        pme_calc_pidx(natoms* thread   /nthread,
+                      natoms*(thread+1)/nthread,
+                      recipbox,x,atc,atc->count_thread[thread]);
+    }
+    /* Non-parallel reduction, since nslab is small */
+
+    for(thread=1; thread<nthread; thread++)
+    {
+        for(slab=0; slab<atc->nslab; slab++)
+        {
+            atc->count_thread[0][slab] += atc->count_thread[thread][slab];
+        }
+    }
+}
+
+static void pme_realloc_splinedata(splinedata_t *spline, pme_atomcomm_t *atc)
+{
+    int i,d;
+
+    srenew(spline->ind,atc->nalloc);
+    /* Initialize the index to identity so it works without threads */
+    for(i=0; i<atc->nalloc; i++)
+    {
+        spline->ind[i] = i;
+    }
+
+    for(d=0;d<DIM;d++)
+    {
+        srenew(spline->theta[d] ,atc->pme_order*atc->nalloc);
+        srenew(spline->dtheta[d],atc->pme_order*atc->nalloc);
+    }
+}
+
 static void pme_realloc_atomcomm_things(pme_atomcomm_t *atc)
 {
-    int nalloc_old,i;
-    
+    int nalloc_old,i,j,nalloc_tpl;
+
     /* We have to avoid a NULL pointer for atc->x to avoid
      * possible fatal errors in MPI routines.
      */
@@ -369,7 +592,7 @@ static void pme_realloc_atomcomm_things(pme_atomcomm_t *atc)
     {
         nalloc_old = atc->nalloc;
         atc->nalloc = over_alloc_dd(max(atc->n,1));
-        
+
         if (atc->nslab > 1) {
             srenew(atc->x,atc->nalloc);
             srenew(atc->q,atc->nalloc);
@@ -380,12 +603,18 @@ static void pme_realloc_atomcomm_things(pme_atomcomm_t *atc)
             }
         }
         if (atc->bSpread) {
-            for(i=0;i<DIM;i++) {
-                srenew(atc->theta[i] ,atc->pme_order*atc->nalloc); 
-                srenew(atc->dtheta[i],atc->pme_order*atc->nalloc);
-            }
-            srenew(atc->fractx,atc->nalloc); 
+            srenew(atc->fractx,atc->nalloc);
             srenew(atc->idx   ,atc->nalloc);
+
+            if (atc->nthread > 1)
+            {
+                srenew(atc->thread_idx,atc->nalloc);
+            }
+
+            for(i=0; i<atc->nthread; i++)
+            {
+                pme_realloc_splinedata(&atc->spline[i],atc);
+            }
         }
     }
 }
@@ -398,7 +627,7 @@ static void pmeredist_pd(gmx_pme_t pme, gmx_bool forw,
 {
     int *idxa;
     int i, ii;
-    
+
     if(FALSE == pme->redist_init) {
         snew(pme->scounts,atc->nslab);
         snew(pme->rcounts,atc->nslab);
@@ -411,19 +640,19 @@ static void pmeredist_pd(gmx_pme_t pme, gmx_bool forw,
         pme->redist_buf_nalloc = over_alloc_dd(n);
         srenew(pme->redist_buf,pme->redist_buf_nalloc*DIM);
     }
-    
+
     pme->idxa = atc->pd;
 
 #ifdef GMX_MPI
     if (forw && bXF) {
-        /* forward, redistribution from pp to pme */ 
-        
+        /* forward, redistribution from pp to pme */
+
         /* Calculate send counts and exchange them with other nodes */
         for(i=0; (i<atc->nslab); i++) pme->scounts[i]=0;
         for(i=0; (i<n); i++) pme->scounts[pme->idxa[i]]++;
         MPI_Alltoall( pme->scounts, 1, MPI_INT, pme->rcounts, 1, MPI_INT, atc->mpi_comm);
-        
-        /* Calculate send and receive displacements and index into send 
+
+        /* Calculate send and receive displacements and index into send
            buffer */
         pme->sdispls[0]=0;
         pme->rdispls[0]=0;
@@ -435,9 +664,9 @@ static void pmeredist_pd(gmx_pme_t pme, gmx_bool forw,
         }
         /* Total # of particles to be received */
         atc->n = pme->rdispls[atc->nslab-1] + pme->rcounts[atc->nslab-1];
-        
+
         pme_realloc_atomcomm_things(atc);
-        
+
         /* Copy particle coordinates into send buffer and exchange*/
         for(i=0; (i<n); i++) {
             ii=DIM*pme->sidx[pme->idxa[i]];
@@ -446,8 +675,8 @@ static void pmeredist_pd(gmx_pme_t pme, gmx_bool forw,
             pme->redist_buf[ii+YY]=x_f[i][YY];
             pme->redist_buf[ii+ZZ]=x_f[i][ZZ];
         }
-        MPI_Alltoallv(pme->redist_buf, pme->scounts, pme->sdispls, 
-                      pme->rvec_mpi, atc->x, pme->rcounts, pme->rdispls, 
+        MPI_Alltoallv(pme->redist_buf, pme->scounts, pme->sdispls,
+                      pme->rvec_mpi, atc->x, pme->rcounts, pme->rdispls,
                       pme->rvec_mpi, atc->mpi_comm);
     }
     if (forw) {
@@ -462,11 +691,11 @@ static void pmeredist_pd(gmx_pme_t pme, gmx_bool forw,
                       atc->q, pme->rcounts, pme->rdispls, mpi_type,
                       atc->mpi_comm);
     }
-    else { /* backward, redistribution from pme to pp */ 
+    else { /* backward, redistribution from pme to pp */
         MPI_Alltoallv(atc->f, pme->rcounts, pme->rdispls, pme->rvec_mpi,
-                      pme->redist_buf, pme->scounts, pme->sdispls, 
+                      pme->redist_buf, pme->scounts, pme->sdispls,
                       pme->rvec_mpi, atc->mpi_comm);
-        
+
         /* Copy data from receive buffer */
         for(i=0; i<atc->nslab; i++)
             pme->sidx[i] = pme->sdispls[i];
@@ -478,7 +707,7 @@ static void pmeredist_pd(gmx_pme_t pme, gmx_bool forw,
             pme->sidx[pme->idxa[i]]++;
         }
     }
-#endif 
+#endif
 }
 
 static void pme_dd_sendrecv(pme_atomcomm_t *atc,
@@ -489,7 +718,7 @@ static void pme_dd_sendrecv(pme_atomcomm_t *atc,
 #ifdef GMX_MPI
     int dest,src;
     MPI_Status stat;
-    
+
     if (bBackward == FALSE) {
         dest = atc->node_dest[shift];
         src  = atc->node_src[shift];
@@ -497,7 +726,7 @@ static void pme_dd_sendrecv(pme_atomcomm_t *atc,
         dest = atc->node_src[shift];
         src  = atc->node_dest[shift];
     }
-    
+
     if (nbyte_s > 0 && nbyte_r > 0) {
         MPI_Sendrecv(buf_s,nbyte_s,MPI_BYTE,
                      dest,shift,
@@ -516,18 +745,18 @@ static void pme_dd_sendrecv(pme_atomcomm_t *atc,
 #endif
 }
 
-static void dd_pmeredist_x_q(gmx_pme_t pme, 
+static void dd_pmeredist_x_q(gmx_pme_t pme,
                              int n, gmx_bool bX, rvec *x, real *charge,
                              pme_atomcomm_t *atc)
 {
     int *commnode,*buf_index;
     int nnodes_comm,i,nsend,local_pos,buf_pos,node,scount,rcount;
-    
+
     commnode  = atc->node_dest;
     buf_index = atc->buf_index;
-    
+
     nnodes_comm = min(2*atc->maxshift,atc->nslab-1);
-    
+
     nsend = 0;
     for(i=0; i<nnodes_comm; i++) {
         buf_index[commnode[i]] = nsend;
@@ -539,13 +768,13 @@ static void dd_pmeredist_x_q(gmx_pme_t pme,
                       "This usually means that your system is not well equilibrated.",
                       n - (atc->count[atc->nodeid] + nsend),
                       pme->nodeid,'x'+atc->dimind);
-        
+
         if (nsend > pme->buf_nalloc) {
             pme->buf_nalloc = over_alloc_dd(nsend);
             srenew(pme->bufv,pme->buf_nalloc);
             srenew(pme->bufr,pme->buf_nalloc);
         }
-        
+
         atc->n = atc->count[atc->nodeid];
         for(i=0; i<nnodes_comm; i++) {
             scount = atc->count[commnode[i]];
@@ -558,10 +787,10 @@ static void dd_pmeredist_x_q(gmx_pme_t pme,
                             &atc->rcount[i],sizeof(int));
             atc->n += atc->rcount[i];
         }
-        
+
         pme_realloc_atomcomm_things(atc);
     }
-    
+
     local_pos = 0;
     for(i=0; i<n; i++) {
         node = atc->pd[i];
@@ -581,7 +810,7 @@ static void dd_pmeredist_x_q(gmx_pme_t pme,
             buf_index[node]++;
         }
     }
-    
+
     buf_pos = 0;
     for(i=0; i<nnodes_comm; i++) {
         scount = atc->count[commnode[i]];
@@ -673,7 +902,7 @@ static void dd_pmeredist_f(gmx_pme_t pme, pme_atomcomm_t *atc,
 }
 
 #ifdef GMX_MPI
-static void 
+static void
 gmx_sum_qgrid_dd(gmx_pme_t pme, real *grid, int direction)
 {
     pme_overlap_t *overlap;
@@ -684,10 +913,10 @@ gmx_sum_qgrid_dd(gmx_pme_t pme, real *grid, int direction)
     int ipulse,send_id,recv_id,datasize;
     real *p;
     real *sendptr,*recvptr;
-    
+
     /* Start with minor-rank communication. This is a bit of a pain since it is not contiguous */
     overlap = &pme->overlap[1];
-    
+
     for(ipulse=0;ipulse<overlap->noverlap_nodes;ipulse++)
     {
         /* Since we have already (un)wrapped the overlap in the z-dimension,
@@ -707,7 +936,7 @@ gmx_sum_qgrid_dd(gmx_pme_t pme, real *grid, int direction)
             send_id = overlap->recv_id[ipulse];
             recv_id = overlap->send_id[ipulse];
             send_index0   = overlap->comm_data[ipulse].recv_index0;
-            send_nindex   = overlap->comm_data[ipulse].recv_nindex;            
+            send_nindex   = overlap->comm_data[ipulse].recv_nindex;
             recv_index0   = overlap->comm_data[ipulse].send_index0;
             recv_nindex   = overlap->comm_data[ipulse].send_nindex;
         }
@@ -731,19 +960,19 @@ gmx_sum_qgrid_dd(gmx_pme_t pme, real *grid, int direction)
                 for(k=0;k<pme->nkz;k++)
                 {
                     iz = k;
-                    pme->pmegrid_sendbuf[icnt++] = grid[ix*(pme->pmegrid_ny*pme->pmegrid_nz)+iy*(pme->pmegrid_nz)+iz];
+                    overlap->sendbuf[icnt++] = grid[ix*(pme->pmegrid_ny*pme->pmegrid_nz)+iy*(pme->pmegrid_nz)+iz];
                 }
             }
         }
-            
+
         datasize      = pme->pmegrid_nx * pme->nkz;
-        
-        MPI_Sendrecv(pme->pmegrid_sendbuf,send_nindex*datasize,GMX_MPI_REAL,
+
+        MPI_Sendrecv(overlap->sendbuf,send_nindex*datasize,GMX_MPI_REAL,
                      send_id,ipulse,
-                     pme->pmegrid_recvbuf,recv_nindex*datasize,GMX_MPI_REAL,
+                     overlap->recvbuf,recv_nindex*datasize,GMX_MPI_REAL,
                      recv_id,ipulse,
                      overlap->mpi_comm,&stat);
-        
+
         /* Get data from contiguous recv buffer */
         if (debug)
         {
@@ -765,24 +994,24 @@ gmx_sum_qgrid_dd(gmx_pme_t pme, real *grid, int direction)
                     iz = k;
                     if(direction==GMX_SUM_QGRID_FORWARD)
                     {
-                        grid[ix*(pme->pmegrid_ny*pme->pmegrid_nz)+iy*(pme->pmegrid_nz)+iz] += pme->pmegrid_recvbuf[icnt++];
+                        grid[ix*(pme->pmegrid_ny*pme->pmegrid_nz)+iy*(pme->pmegrid_nz)+iz] += overlap->recvbuf[icnt++];
                     }
                     else
                     {
-                        grid[ix*(pme->pmegrid_ny*pme->pmegrid_nz)+iy*(pme->pmegrid_nz)+iz]  = pme->pmegrid_recvbuf[icnt++];
+                        grid[ix*(pme->pmegrid_ny*pme->pmegrid_nz)+iy*(pme->pmegrid_nz)+iz]  = overlap->recvbuf[icnt++];
                     }
                 }
             }
         }
     }
-    
+
     /* Major dimension is easier, no copying required,
      * but we might have to sum to separate array.
      * Since we don't copy, we have to communicate up to pmegrid_nz,
      * not nkz as for the minor direction.
      */
     overlap = &pme->overlap[0];
-    
+
     for(ipulse=0;ipulse<overlap->noverlap_nodes;ipulse++)
     {
         if(direction==GMX_SUM_QGRID_FORWARD)
@@ -793,19 +1022,19 @@ gmx_sum_qgrid_dd(gmx_pme_t pme, real *grid, int direction)
             send_nindex   = overlap->comm_data[ipulse].send_nindex;
             recv_index0   = overlap->comm_data[ipulse].recv_index0;
             recv_nindex   = overlap->comm_data[ipulse].recv_nindex;
-            recvptr   = pme->pmegrid_recvbuf;
+            recvptr   = overlap->recvbuf;
         }
         else
         {
             send_id = overlap->recv_id[ipulse];
             recv_id = overlap->send_id[ipulse];
             send_index0   = overlap->comm_data[ipulse].recv_index0;
-            send_nindex   = overlap->comm_data[ipulse].recv_nindex;            
+            send_nindex   = overlap->comm_data[ipulse].recv_nindex;
             recv_index0   = overlap->comm_data[ipulse].send_index0;
             recv_nindex   = overlap->comm_data[ipulse].send_nindex;
             recvptr   = grid + (recv_index0-pme->pmegrid_start_ix)*(pme->pmegrid_ny*pme->pmegrid_nz);
         }
-                
+
         sendptr       = grid + (send_index0-pme->pmegrid_start_ix)*(pme->pmegrid_ny*pme->pmegrid_nz);
         datasize      = pme->pmegrid_ny * pme->pmegrid_nz;
 
@@ -828,14 +1057,14 @@ gmx_sum_qgrid_dd(gmx_pme_t pme, real *grid, int direction)
                      recvptr,recv_nindex*datasize,GMX_MPI_REAL,
                      recv_id,ipulse,
                      overlap->mpi_comm,&stat);
-        
+
         /* ADD data from contiguous recv buffer */
         if(direction==GMX_SUM_QGRID_FORWARD)
-        {        
+        {
             p = grid + (recv_index0-pme->pmegrid_start_ix)*(pme->pmegrid_ny*pme->pmegrid_nz);
             for(i=0;i<recv_nindex*datasize;i++)
             {
-                p[i] += pme->pmegrid_recvbuf[i];
+                p[i] += overlap->recvbuf[i];
             }
         }
     }
@@ -856,12 +1085,12 @@ copy_pmegrid_to_fftgrid(gmx_pme_t pme, real *pmegrid, real *fftgrid)
                                    local_fft_ndata,
                                    local_fft_offset,
                                    local_fft_size);
-    
+
     local_pme_size[0] = pme->pmegrid_nx;
     local_pme_size[1] = pme->pmegrid_ny;
     local_pme_size[2] = pme->pmegrid_nz;
-    
-    /* The fftgrid is always 'justified' to the lower-left corner of the PME grid, 
+
+    /* The fftgrid is always 'justified' to the lower-left corner of the PME grid,
      the offset is identical, and the PME grid always has more data (due to overlap)
      */
     {
@@ -875,6 +1104,7 @@ copy_pmegrid_to_fftgrid(gmx_pme_t pme, real *pmegrid, real *fftgrid)
         fp2 = ffopen(fn,"w");
      sprintf(format,"%s%s\n",pdbformat,"%6.2f%6.2f");
 #endif
+
     for(ix=0;ix<local_fft_ndata[XX];ix++)
     {
         for(iy=0;iy<local_fft_ndata[YY];iy++)
@@ -901,22 +1131,42 @@ copy_pmegrid_to_fftgrid(gmx_pme_t pme, real *pmegrid, real *fftgrid)
         }
     }
 #ifdef DEBUG_PME
-    fclose(fp);
-    fclose(fp2);
+    ffclose(fp);
+    ffclose(fp2);
 #endif
     }
     return 0;
 }
 
 
+static gmx_cycles_t omp_cyc_start()
+{
+    return gmx_cycles_read();
+}
+
+static gmx_cycles_t omp_cyc_end(gmx_cycles_t c)
+{
+    return gmx_cycles_read() - c;
+}
+
+
 static int
-copy_fftgrid_to_pmegrid(gmx_pme_t pme, real *fftgrid, real *pmegrid)
+copy_fftgrid_to_pmegrid(gmx_pme_t pme, const real *fftgrid, real *pmegrid,
+                        int nthread,int thread)
 {
     ivec    local_fft_ndata,local_fft_offset,local_fft_size;
     ivec    local_pme_size;
-    int     i,ix,iy,iz;
+    int     ixy0,ixy1,ixy,ix,iy,iz;
     int     pmeidx,fftidx;
-    
+#ifdef PME_TIME_THREADS
+    gmx_cycles_t c1;
+    static double cs1=0;
+    static int cnt=0;
+#endif
+
+#ifdef PME_TIME_THREADS
+    c1 = omp_cyc_start();
+#endif
     /* Dimensions should be identical for A/B grid, so we just use A here */
     gmx_parallel_3dfft_real_limits(pme->pfft_setupA,
                                    local_fft_ndata,
@@ -926,22 +1176,36 @@ copy_fftgrid_to_pmegrid(gmx_pme_t pme, real *fftgrid, real *pmegrid)
     local_pme_size[0] = pme->pmegrid_nx;
     local_pme_size[1] = pme->pmegrid_ny;
     local_pme_size[2] = pme->pmegrid_nz;
-    
-    /* The fftgrid is always 'justified' to the lower-left corner of the PME grid, 
+
+    /* The fftgrid is always 'justified' to the lower-left corner of the PME grid,
      the offset is identical, and the PME grid always has more data (due to overlap)
      */
-    for(ix=0;ix<local_fft_ndata[XX];ix++)
+    ixy0 = ((thread  )*local_fft_ndata[XX]*local_fft_ndata[YY])/nthread;
+    ixy1 = ((thread+1)*local_fft_ndata[XX]*local_fft_ndata[YY])/nthread;
+
+    for(ixy=ixy0;ixy<ixy1;ixy++)
     {
-        for(iy=0;iy<local_fft_ndata[YY];iy++)
+        ix = ixy/local_fft_ndata[YY];
+        iy = ixy - ix*local_fft_ndata[YY];
+
+        pmeidx = (ix*local_pme_size[YY] + iy)*local_pme_size[ZZ];
+        fftidx = (ix*local_fft_size[YY] + iy)*local_fft_size[ZZ];
+        for(iz=0;iz<local_fft_ndata[ZZ];iz++)
         {
-            for(iz=0;iz<local_fft_ndata[ZZ];iz++)
-            {
-                pmeidx = ix*(local_pme_size[YY]*local_pme_size[ZZ])+iy*(local_pme_size[ZZ])+iz;
-                fftidx = ix*(local_fft_size[YY]*local_fft_size[ZZ])+iy*(local_fft_size[ZZ])+iz;
-                pmegrid[pmeidx] = fftgrid[fftidx];
-            }
+            pmegrid[pmeidx+iz] = fftgrid[fftidx+iz];
         }
-    }   
+    }
+
+#ifdef PME_TIME_THREADS
+    c1 = omp_cyc_end(c1);
+    cs1 += (double)c1;
+    cnt++;
+    if (cnt % 20 == 0)
+    {
+        printf("copy %.2f\n",cs1*1e-9);
+    }
+#endif
+
     return 0;
 }
 
@@ -962,9 +1226,9 @@ wrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
     overlap = pme->pme_order - 1;
 
     /* Add periodic overlap in z */
-    for(ix=0; ix<pnx; ix++)
+    for(ix=0; ix<pme->pmegrid_nx; ix++)
     {
-        for(iy=0; iy<pny; iy++)
+        for(iy=0; iy<pme->pmegrid_ny; iy++)
         {
             for(iz=0; iz<overlap; iz++)
             {
@@ -976,7 +1240,7 @@ wrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
 
     if (pme->nnodes_minor == 1)
     {
-       for(ix=0; ix<pnx; ix++)
+       for(ix=0; ix<pme->pmegrid_nx; ix++)
        {
            for(iy=0; iy<overlap; iy++)
            {
@@ -988,10 +1252,10 @@ wrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
            }
        }
     }
-     
+
     if (pme->nnodes_major == 1)
     {
-        ny_x = (pme->nnodes_minor == 1 ? ny : pny);
+        ny_x = (pme->nnodes_minor == 1 ? ny : pme->pmegrid_ny);
 
         for(ix=0; ix<overlap; ix++)
         {
@@ -1011,7 +1275,7 @@ wrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
 static void
 unwrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
 {
-    int     nx,ny,nz,pnx,pny,pnz,ny_x,overlap,ix,iy,iz;
+    int     nx,ny,nz,pnx,pny,pnz,ny_x,overlap,ix;
 
     nx = pme->nkx;
     ny = pme->nky;
@@ -1025,10 +1289,12 @@ unwrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
 
     if (pme->nnodes_major == 1)
     {
-        ny_x = (pme->nnodes_minor == 1 ? ny : pny);
+        ny_x = (pme->nnodes_minor == 1 ? ny : pme->pmegrid_ny);
 
         for(ix=0; ix<overlap; ix++)
         {
+            int iy,iz;
+
             for(iy=0; iy<ny_x; iy++)
             {
                 for(iz=0; iz<nz; iz++)
@@ -1042,8 +1308,11 @@ unwrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
 
     if (pme->nnodes_minor == 1)
     {
-       for(ix=0; ix<pnx; ix++)
+#pragma omp parallel for num_threads(pme->nthread) schedule(static)
+       for(ix=0; ix<pme->pmegrid_nx; ix++)
        {
+           int iy,iz;
+
            for(iy=0; iy<overlap; iy++)
            {
                for(iz=0; iz<nz; iz++)
@@ -1056,9 +1325,12 @@ unwrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
     }
 
     /* Copy periodic overlap in z */
-    for(ix=0; ix<pnx; ix++)
+#pragma omp parallel for num_threads(pme->nthread) schedule(static)
+    for(ix=0; ix<pme->pmegrid_nx; ix++)
     {
-        for(iy=0; iy<pny; iy++)
+        int iy,iz;
+
+        for(iy=0; iy<pme->pmegrid_ny; iy++)
         {
             for(iz=0; iz<overlap; iz++)
             {
@@ -1069,6 +1341,51 @@ unwrap_periodic_pmegrid(gmx_pme_t pme, real *pmegrid)
     }
 }
 
+static void clear_grid(int nx,int ny,int nz,real *grid,
+                       ivec fs,int *flag,
+                       int fx,int fy,int fz,
+                       int order)
+{
+    int nc,ncz;
+    int fsx,fsy,fsz,gx,gy,gz,g0x,g0y,x,y,z;
+    int flind;
+
+    nc  = 2 + (order - 2)/FLBS;
+    ncz = 2 + (order - 2)/FLBSZ;
+
+    for(fsx=fx; fsx<fx+nc; fsx++)
+    {
+        for(fsy=fy; fsy<fy+nc; fsy++)
+        {
+            for(fsz=fz; fsz<fz+ncz; fsz++)
+            {
+                flind = (fsx*fs[YY] + fsy)*fs[ZZ] + fsz;
+                if (flag[flind] == 0)
+                {
+                    gx = fsx*FLBS;
+                    gy = fsy*FLBS;
+                    gz = fsz*FLBSZ;
+                    g0x = (gx*ny + gy)*nz + gz;
+                    for(x=0; x<FLBS; x++)
+                    {
+                        g0y = g0x;
+                        for(y=0; y<FLBS; y++)
+                        {
+                            for(z=0; z<FLBSZ; z++)
+                            {
+                                grid[g0y+z] = 0;
+                            }
+                            g0y += nz;
+                        }
+                        g0x += ny*nz;
+                    }
+
+                    flag[flind] = 1;
+                }
+            }
+        }
+    }
+}
 
 /* This has to be a macro to enable full compiler optimization with xlC (and probably others too) */
 #define DO_BSPLINE(order)                            \
@@ -1091,11 +1408,13 @@ for(ithx=0; (ithx<order); ithx++)                    \
 }
 
 
-static void spread_q_bsplines(gmx_pme_t pme, pme_atomcomm_t *atc, 
-                              real *grid)
+static void spread_q_bsplines_thread(pmegrid_t *pmegrid,
+                                     pme_atomcomm_t *atc, splinedata_t *spline,
+                                     pme_spline_work_t *work)
 {
 
     /* spread charges from home atoms to local grid */
+    real     *grid;
     pme_overlap_t *ol;
     int      b,i,nn,n,ithx,ithy,ithz,i0,j0,k0;
     int *    idxptr;
@@ -1103,302 +1422,662 @@ static void spread_q_bsplines(gmx_pme_t pme, pme_atomcomm_t *atc,
     real     valx,valxy,qn;
     real     *thx,*thy,*thz;
     int      localsize, bndsize;
-  
     int      pnx,pny,pnz,ndatatot;
-  
-    pnx = pme->pmegrid_nx;
-    pny = pme->pmegrid_ny;
-    pnz = pme->pmegrid_nz;
+    int      offx,offy,offz;
+
+    pnx = pmegrid->n[XX];
+    pny = pmegrid->n[YY];
+    pnz = pmegrid->n[ZZ];
+
+    offx = pmegrid->offset[XX];
+    offy = pmegrid->offset[YY];
+    offz = pmegrid->offset[ZZ];
+
     ndatatot = pnx*pny*pnz;
-    
+    grid = pmegrid->grid;
     for(i=0;i<ndatatot;i++)
     {
         grid[i] = 0;
     }
 
-    order = pme->pme_order;
+    order = pmegrid->order;
 
-    for(nn=0; (nn<atc->n);nn++) 
+    for(nn=0; nn<spline->n; nn++)
     {
-        n      = nn;
-        qn     = atc->q[n];
+        n  = spline->ind[nn];
+        qn = atc->q[n];
 
-        if (qn != 0) 
+        if (qn != 0)
         {
             idxptr = atc->idx[n];
-            norder = n*order;
-            
-            i0   = idxptr[XX]; 
-            j0   = idxptr[YY];
-            k0   = idxptr[ZZ];
-            thx = atc->theta[XX] + norder;
-            thy = atc->theta[YY] + norder;
-            thz = atc->theta[ZZ] + norder;
-            
+            norder = nn*order;
+
+            i0   = idxptr[XX] - offx;
+            j0   = idxptr[YY] - offy;
+            k0   = idxptr[ZZ] - offz;
+
+            thx = spline->theta[XX] + norder;
+            thy = spline->theta[YY] + norder;
+            thz = spline->theta[ZZ] + norder;
+
             switch (order) {
-            case 4:  DO_BSPLINE(4);     break;
-            case 5:  DO_BSPLINE(5);     break;
-            default: DO_BSPLINE(order); break;
+            case 4:
+#ifdef PME_SSE
+#ifdef PME_SSE_UNALIGNED
+#define PME_SPREAD_SSE_ORDER4
+#else
+#define PME_SPREAD_SSE_ALIGNED
+#define PME_ORDER 4
+#endif
+#include "pme_sse_single.h"
+#else
+                DO_BSPLINE(4);
+#endif
+                break;
+            case 5:
+#ifdef PME_SSE
+#define PME_SPREAD_SSE_ALIGNED
+#define PME_ORDER 5
+#include "pme_sse_single.h"
+#else
+                DO_BSPLINE(5);
+#endif
+                break;
+            default:
+                DO_BSPLINE(order);
+                break;
             }
         }
-    }  
+    }
 }
 
-
-#if ( !defined(GMX_DOUBLE) && ( defined(GMX_IA32_SSE) || defined(GMX_X86_64_SSE) || defined(GMX_X86_64_SSE2) ) )
-    /* Calculate exponentials through SSE in float precision */
-#define CALC_EXPONENTIALS(start,end,r_aligned)      \
-    {                                               \
-        __m128 tmp_sse;                             \
-        for(kx=0; kx<end; kx+=4)                    \
-        {                                           \
-            tmp_sse = _mm_load_ps(r_aligned+kx);    \
-            tmp_sse = gmx_mm_exp_ps(tmp_sse);       \
-            _mm_store_ps(r_aligned+kx,tmp_sse);     \
-        }                                           \
+static void set_grid_alignment(int *pmegrid_nz,int pme_order)
+{
+#ifdef PME_SSE
+    if (pme_order == 5
+#ifndef PME_SSE_UNALIGNED
+        || pme_order == 4
+#endif
+        )
+    {
+        /* Round nz up to a multiple of 4 to ensure alignment */
+        *pmegrid_nz = ((*pmegrid_nz + 3) & ~3);
     }
-#else
-#define CALC_EXPONENTIALS(start,end,r)          \
-    for(kx=start; kx<end; kx++)                 \
-    {                                           \
-        r[kx] = exp(r[kx]);                     \
+#endif
+}
+
+static void set_gridsize_alignment(int *gridsize,int pme_order)
+{
+#ifdef PME_SSE
+#ifndef PME_SSE_UNALIGNED
+    if (pme_order == 4)
+    {
+        /* Add extra elements to ensured aligned operations do not go
+         * beyond the allocated grid size.
+         * Note that for pme_order=5, the pme grid z-size alignment
+         * ensures that we will not go beyond the grid size.
+         */
+         *gridsize += 4;
     }
 #endif
+#endif
+}
+
+static void pmegrid_init(pmegrid_t *grid,
+                         int cx, int cy, int cz,
+                         int x0, int y0, int z0,
+                         int x1, int y1, int z1,
+                         gmx_bool set_alignment,
+                         int pme_order,
+                         real *ptr)
+{
+    int nz,gridsize;
+
+    grid->ci[XX] = cx;
+    grid->ci[YY] = cy;
+    grid->ci[ZZ] = cz;
+    grid->offset[XX] = x0;
+    grid->offset[YY] = y0;
+    grid->offset[ZZ] = z0;
+    grid->n[XX]      = x1 - x0 + pme_order - 1;
+    grid->n[YY]      = y1 - y0 + pme_order - 1;
+    grid->n[ZZ]      = z1 - z0 + pme_order - 1;
+
+    nz = grid->n[ZZ];
+    set_grid_alignment(&nz,pme_order);
+    if (set_alignment)
+    {
+        grid->n[ZZ] = nz;
+    }
+    else if (nz != grid->n[ZZ])
+    {
+        gmx_incons("pmegrid_init call with an unaligned z size");
+    }
 
+    grid->order = pme_order;
+    if (ptr == NULL)
+    {
+        gridsize = grid->n[XX]*grid->n[YY]*grid->n[ZZ];
+        set_gridsize_alignment(&gridsize,pme_order);
+        snew_aligned(grid->grid,gridsize,16);
+    }
+    else
+    {
+        grid->grid = ptr;
+    }
+}
 
-static int solve_pme_yzx(gmx_pme_t pme,t_complex *grid,
-                         real ewaldcoeff,real vol,
-                         gmx_bool bEnerVir,real *mesh_energy,matrix vir)
+static int div_round_up(int enumerator,int denominator)
 {
-    /* do recip sum over local cells in grid */
-    /* y major, z middle, x minor or continuous */
-    t_complex *p0;
+    return (enumerator + denominator - 1)/denominator;
+}
+
+static void make_subgrid_division(const ivec n,int ovl,int nthread,
+                                  ivec nsub)
+{
+    int gsize_opt,gsize;
+    int nsx,nsy,nsz;
+    char *env;
+
+    gsize_opt = -1;
+    for(nsx=1; nsx<=nthread; nsx++)
+    {
+        if (nthread % nsx == 0)
+        {
+            for(nsy=1; nsy<=nthread; nsy++)
+            {
+                if (nsx*nsy <= nthread && nthread % (nsx*nsy) == 0)
+                {
+                    nsz = nthread/(nsx*nsy);
+
+                    /* Determine the number of grid points per thread */
+                    gsize =
+                        (div_round_up(n[XX],nsx) + ovl)*
+                        (div_round_up(n[YY],nsy) + ovl)*
+                        (div_round_up(n[ZZ],nsz) + ovl);
+
+                    /* Minimize the number of grids points per thread
+                     * and, secondarily, the number of cuts in minor dimensions.
+                     */
+                    if (gsize_opt == -1 ||
+                        gsize < gsize_opt ||
+                        (gsize == gsize_opt &&
+                         (nsz < nsub[ZZ] || (nsz == nsub[ZZ] && nsy < nsub[YY]))))
+                    {
+                        nsub[XX] = nsx;
+                        nsub[YY] = nsy;
+                        nsub[ZZ] = nsz;
+                        gsize_opt = gsize;
+                    }
+                }
+            }
+        }
+    }
+
+    env = getenv("GMX_PME_THREAD_DIVISION");
+    if (env != NULL)
+    {
+        sscanf(env,"%d %d %d",&nsub[XX],&nsub[YY],&nsub[ZZ]);
+    }
+
+    if (nsub[XX]*nsub[YY]*nsub[ZZ] != nthread)
+    {
+        gmx_fatal(FARGS,"PME grid thread division (%d x %d x %d) does not match the total number of threads (%d)",nsub[XX],nsub[YY],nsub[ZZ],nthread);
+    }
+}
+
+static void pmegrids_init(pmegrids_t *grids,
+                          int nx,int ny,int nz,int nz_base,
+                          int pme_order,
+                          int nthread,
+                          int overlap_x,
+                          int overlap_y)
+{
+    ivec n,n_base,g0,g1;
+    int t,x,y,z,d,i,tfac;
+    int max_comm_lines;
+
+    n[XX] = nx - (pme_order - 1);
+    n[YY] = ny - (pme_order - 1);
+    n[ZZ] = nz - (pme_order - 1);
+
+    copy_ivec(n,n_base);
+    n_base[ZZ] = nz_base;
+
+    pmegrid_init(&grids->grid,0,0,0,0,0,0,n[XX],n[YY],n[ZZ],FALSE,pme_order,
+                 NULL);
+
+    grids->nthread = nthread;
+
+    make_subgrid_division(n_base,pme_order-1,grids->nthread,grids->nc);
+
+    if (grids->nthread > 1)
+    {
+        ivec nst;
+        int gridsize;
+        real *grid_all;
+
+        for(d=0; d<DIM; d++)
+        {
+            nst[d] = div_round_up(n[d],grids->nc[d]) + pme_order - 1;
+        }
+        set_grid_alignment(&nst[ZZ],pme_order);
+
+        if (debug)
+        {
+            fprintf(debug,"pmegrid thread local division: %d x %d x %d\n",
+                    grids->nc[XX],grids->nc[YY],grids->nc[ZZ]);
+            fprintf(debug,"pmegrid %d %d %d max thread pmegrid %d %d %d\n",
+                    nx,ny,nz,
+                    nst[XX],nst[YY],nst[ZZ]);
+        }
+
+        snew(grids->grid_th,grids->nthread);
+        t = 0;
+        gridsize = nst[XX]*nst[YY]*nst[ZZ];
+        set_gridsize_alignment(&gridsize,pme_order);
+        snew_aligned(grid_all,
+                     grids->nthread*gridsize+(grids->nthread+1)*GMX_CACHE_SEP,
+                     16);
+
+        for(x=0; x<grids->nc[XX]; x++)
+        {
+            for(y=0; y<grids->nc[YY]; y++)
+            {
+                for(z=0; z<grids->nc[ZZ]; z++)
+                {
+                    pmegrid_init(&grids->grid_th[t],
+                                 x,y,z,
+                                 (n[XX]*(x  ))/grids->nc[XX],
+                                 (n[YY]*(y  ))/grids->nc[YY],
+                                 (n[ZZ]*(z  ))/grids->nc[ZZ],
+                                 (n[XX]*(x+1))/grids->nc[XX],
+                                 (n[YY]*(y+1))/grids->nc[YY],
+                                 (n[ZZ]*(z+1))/grids->nc[ZZ],
+                                 TRUE,
+                                 pme_order,
+                                 grid_all+GMX_CACHE_SEP+t*(gridsize+GMX_CACHE_SEP));
+                    t++;
+                }
+            }
+        }
+    }
+
+    snew(grids->g2t,DIM);
+    tfac = 1;
+    for(d=DIM-1; d>=0; d--)
+    {
+        snew(grids->g2t[d],n[d]);
+        t = 0;
+        for(i=0; i<n[d]; i++)
+        {
+            /* The second check should match the parameters
+             * of the pmegrid_init call above.
+             */
+            while (t + 1 < grids->nc[d] && i >= (n[d]*(t+1))/grids->nc[d])
+            {
+                t++;
+            }
+            grids->g2t[d][i] = t*tfac;
+        }
+
+        tfac *= grids->nc[d];
+
+        switch (d)
+        {
+        case XX: max_comm_lines = overlap_x;     break;
+        case YY: max_comm_lines = overlap_y;     break;
+        case ZZ: max_comm_lines = pme_order - 1; break;
+        }
+        grids->nthread_comm[d] = 0;
+        while ((n[d]*grids->nthread_comm[d])/grids->nc[d] < max_comm_lines)
+        {
+            grids->nthread_comm[d]++;
+        }
+        if (debug != NULL)
+        {
+            fprintf(debug,"pmegrid thread grid communication range in %c: %d\n",
+                    'x'+d,grids->nthread_comm[d]);
+        }
+        /* It should be possible to make grids->nthread_comm[d]==grids->nc[d]
+         * work, but this is not a problematic restriction.
+         */
+        if (grids->nc[d] > 1 && grids->nthread_comm[d] > grids->nc[d])
+        {
+            gmx_fatal(FARGS,"Too many threads for PME (%d) compared to the number of grid lines, reduce the number of threads doing PME",grids->nthread);
+        }
+    }
+}
+
+
+static void pmegrids_destroy(pmegrids_t *grids)
+{
+    int t;
+
+    if (grids->grid.grid != NULL)
+    {
+        sfree(grids->grid.grid);
+
+        if (grids->nthread > 0)
+        {
+            for(t=0; t<grids->nthread; t++)
+            {
+                sfree(grids->grid_th[t].grid);
+            }
+            sfree(grids->grid_th);
+        }
+    }
+}
+
+
+static void realloc_work(pme_work_t *work,int nkx)
+{
+    if (nkx > work->nalloc)
+    {
+        work->nalloc = nkx;
+        srenew(work->mhx  ,work->nalloc);
+        srenew(work->mhy  ,work->nalloc);
+        srenew(work->mhz  ,work->nalloc);
+        srenew(work->m2   ,work->nalloc);
+        /* Allocate an aligned pointer for SSE operations, including 3 extra
+         * elements at the end since SSE operates on 4 elements at a time.
+         */
+        sfree_aligned(work->denom);
+        sfree_aligned(work->tmp1);
+        sfree_aligned(work->eterm);
+        snew_aligned(work->denom,work->nalloc+3,16);
+        snew_aligned(work->tmp1 ,work->nalloc+3,16);
+        snew_aligned(work->eterm,work->nalloc+3,16);
+        srenew(work->m2inv,work->nalloc);
+    }
+}
+
+
+static void free_work(pme_work_t *work)
+{
+    sfree(work->mhx);
+    sfree(work->mhy);
+    sfree(work->mhz);
+    sfree(work->m2);
+    sfree_aligned(work->denom);
+    sfree_aligned(work->tmp1);
+    sfree_aligned(work->eterm);
+    sfree(work->m2inv);
+}
+
+
+#ifdef PME_SSE
+    /* Calculate exponentials through SSE in float precision */
+inline static void calc_exponentials(int start, int end, real f, real *d_aligned, real *r_aligned, real *e_aligned)
+{
+    {
+        const __m128 two = _mm_set_ps(2.0f,2.0f,2.0f,2.0f);
+        __m128 f_sse;
+        __m128 lu;
+        __m128 tmp_d1,d_inv,tmp_r,tmp_e;
+        int kx;
+        f_sse = _mm_load1_ps(&f);
+        for(kx=0; kx<end; kx+=4)
+        {
+            tmp_d1   = _mm_load_ps(d_aligned+kx);
+            lu       = _mm_rcp_ps(tmp_d1);
+            d_inv    = _mm_mul_ps(lu,_mm_sub_ps(two,_mm_mul_ps(lu,tmp_d1)));
+            tmp_r    = _mm_load_ps(r_aligned+kx);
+            tmp_r    = gmx_mm_exp_ps(tmp_r);
+            tmp_e    = _mm_mul_ps(f_sse,d_inv);
+            tmp_e    = _mm_mul_ps(tmp_e,tmp_r);
+            _mm_store_ps(e_aligned+kx,tmp_e);
+        }
+    }
+}
+#else
+inline static void calc_exponentials(int start, int end, real f, real *d, real *r, real *e)
+{
+    int kx;
+    for(kx=start; kx<end; kx++)
+    {
+        d[kx] = 1.0/d[kx];
+    }
+    for(kx=start; kx<end; kx++)
+    {
+        r[kx] = exp(r[kx]);
+    }
+    for(kx=start; kx<end; kx++)
+    {
+        e[kx] = f*r[kx]*d[kx];
+    }
+}
+#endif
+
+
+static int solve_pme_yzx(gmx_pme_t pme,t_complex *grid,
+                         real ewaldcoeff,real vol,
+                         gmx_bool bEnerVir,
+                         int nthread,int thread)
+{
+    /* do recip sum over local cells in grid */
+    /* y major, z middle, x minor or continuous */
+    t_complex *p0;
     int     kx,ky,kz,maxkx,maxky,maxkz;
-    int     nx,ny,nz,iy,iz,kxstart,kxend;
+    int     nx,ny,nz,iyz0,iyz1,iyz,iy,iz,kxstart,kxend;
     real    mx,my,mz;
     real    factor=M_PI*M_PI/(ewaldcoeff*ewaldcoeff);
     real    ets2,struct2,vfactor,ets2vf;
-    real    eterm,d1,d2,energy=0;
+    real    d1,d2,energy=0;
     real    by,bz;
     real    virxx=0,virxy=0,virxz=0,viryy=0,viryz=0,virzz=0;
     real    rxx,ryx,ryy,rzx,rzy,rzz;
-       real    *mhx,*mhy,*mhz,*m2,*denom,*tmp1,*m2inv;
+    pme_work_t *work;
+    real    *mhx,*mhy,*mhz,*m2,*denom,*tmp1,*eterm,*m2inv;
     real    mhxk,mhyk,mhzk,m2k;
     real    corner_fac;
     ivec    complex_order;
     ivec    local_ndata,local_offset,local_size;
-    
+    real    elfac;
+
+    elfac = ONE_4PI_EPS0/pme->epsilon_r;
+
     nx = pme->nkx;
     ny = pme->nky;
     nz = pme->nkz;
-    
+
     /* Dimensions should be identical for A/B grid, so we just use A here */
     gmx_parallel_3dfft_complex_limits(pme->pfft_setupA,
                                       complex_order,
                                       local_ndata,
                                       local_offset,
                                       local_size);
-    
+
     rxx = pme->recipbox[XX][XX];
     ryx = pme->recipbox[YY][XX];
     ryy = pme->recipbox[YY][YY];
     rzx = pme->recipbox[ZZ][XX];
     rzy = pme->recipbox[ZZ][YY];
     rzz = pme->recipbox[ZZ][ZZ];
-    
+
     maxkx = (nx+1)/2;
     maxky = (ny+1)/2;
     maxkz = nz/2+1;
-       
-       mhx   = pme->work_mhx;
-       mhy   = pme->work_mhy;
-       mhz   = pme->work_mhz;
-       m2    = pme->work_m2;
-       denom = pme->work_denom;
-       tmp1  = pme->work_tmp1;
-       m2inv = pme->work_m2inv;        
 
-    for(iy=0;iy<local_ndata[YY];iy++)
+    work = &pme->work[thread];
+    mhx   = work->mhx;
+    mhy   = work->mhy;
+    mhz   = work->mhz;
+    m2    = work->m2;
+    denom = work->denom;
+    tmp1  = work->tmp1;
+    eterm = work->eterm;
+    m2inv = work->m2inv;
+
+    iyz0 = local_ndata[YY]*local_ndata[ZZ]* thread   /nthread;
+    iyz1 = local_ndata[YY]*local_ndata[ZZ]*(thread+1)/nthread;
+
+    for(iyz=iyz0; iyz<iyz1; iyz++)
     {
+        iy = iyz/local_ndata[ZZ];
+        iz = iyz - iy*local_ndata[ZZ];
+
         ky = iy + local_offset[YY];
-        
-        if (ky < maxky) 
+
+        if (ky < maxky)
         {
             my = ky;
         }
-        else 
+        else
         {
             my = (ky - ny);
         }
-        
+
         by = M_PI*vol*pme->bsp_mod[YY][ky];
 
-        for(iz=0;iz<local_ndata[ZZ];iz++)
-        {
-            kz = iz + local_offset[ZZ];
-            
-            mz = kz;
-
-            bz = pme->bsp_mod[ZZ][kz];
-            
-            /* 0.5 correction for corner points */
-                       corner_fac = 1;
-            if (kz == 0)
-                corner_fac = 0.5;
-            if (kz == (nz+1)/2)
-                corner_fac = 0.5;
-                      
-            p0 = grid + iy*local_size[ZZ]*local_size[XX] + iz*local_size[XX];
-            
-            /* We should skip the k-space point (0,0,0) */
-            if (local_offset[XX] > 0 ||
-                local_offset[YY] > 0 || ky > 0 ||
-                kz > 0)
+        kz = iz + local_offset[ZZ];
+
+        mz = kz;
+
+        bz = pme->bsp_mod[ZZ][kz];
+
+        /* 0.5 correction for corner points */
+        corner_fac = 1;
+        if (kz == 0 || kz == (nz+1)/2)
+        {
+            corner_fac = 0.5;
+        }
+
+        p0 = grid + iy*local_size[ZZ]*local_size[XX] + iz*local_size[XX];
+
+        /* We should skip the k-space point (0,0,0) */
+        if (local_offset[XX] > 0 || ky > 0 || kz > 0)
+        {
+            kxstart = local_offset[XX];
+        }
+        else
+        {
+            kxstart = local_offset[XX] + 1;
+            p0++;
+        }
+        kxend = local_offset[XX] + local_ndata[XX];
+
+        if (bEnerVir)
+        {
+            /* More expensive inner loop, especially because of the storage
+             * of the mh elements in array's.
+             * Because x is the minor grid index, all mh elements
+             * depend on kx for triclinic unit cells.
+             */
+
+                /* Two explicit loops to avoid a conditional inside the loop */
+            for(kx=kxstart; kx<maxkx; kx++)
             {
-                kxstart = local_offset[XX];
+                mx = kx;
+
+                mhxk      = mx * rxx;
+                mhyk      = mx * ryx + my * ryy;
+                mhzk      = mx * rzx + my * rzy + mz * rzz;
+                m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
+                mhx[kx]   = mhxk;
+                mhy[kx]   = mhyk;
+                mhz[kx]   = mhzk;
+                m2[kx]    = m2k;
+                denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
+                tmp1[kx]  = -factor*m2k;
             }
-            else
+
+            for(kx=maxkx; kx<kxend; kx++)
             {
-                kxstart = local_offset[XX] + 1;
-                p0++;
+                mx = (kx - nx);
+
+                mhxk      = mx * rxx;
+                mhyk      = mx * ryx + my * ryy;
+                mhzk      = mx * rzx + my * rzy + mz * rzz;
+                m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
+                mhx[kx]   = mhxk;
+                mhy[kx]   = mhyk;
+                mhz[kx]   = mhzk;
+                m2[kx]    = m2k;
+                denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
+                tmp1[kx]  = -factor*m2k;
             }
-            kxend = local_offset[XX] + local_ndata[XX];
-                       
-            if (bEnerVir)
+
+            for(kx=kxstart; kx<kxend; kx++)
             {
-                /* More expensive inner loop, especially because of the storage
-                 * of the mh elements in array's.
-                 * Because x is the minor grid index, all mh elements
-                 * depend on kx for triclinic unit cells.
-                 */
+                m2inv[kx] = 1.0/m2[kx];
+            }
 
-                /* Two explicit loops to avoid a conditional inside the loop */
-                for(kx=kxstart; kx<maxkx; kx++)
-                {
-                    mx = kx;
-                    
-                    mhxk      = mx * rxx;
-                    mhyk      = mx * ryx + my * ryy;
-                    mhzk      = mx * rzx + my * rzy + mz * rzz;
-                    m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
-                    mhx[kx]   = mhxk;
-                    mhy[kx]   = mhyk;
-                    mhz[kx]   = mhzk;
-                    m2[kx]    = m2k;
-                    denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
-                    tmp1[kx]  = -factor*m2k;
-                }
-                
-                for(kx=maxkx; kx<kxend; kx++)
-                {
-                    mx = (kx - nx);
-
-                    mhxk      = mx * rxx;
-                    mhyk      = mx * ryx + my * ryy;
-                    mhzk      = mx * rzx + my * rzy + mz * rzz;
-                    m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
-                    mhx[kx]   = mhxk;
-                    mhy[kx]   = mhyk;
-                    mhz[kx]   = mhzk;
-                    m2[kx]    = m2k;
-                    denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
-                    tmp1[kx]  = -factor*m2k;
-                }
-                
-                for(kx=kxstart; kx<kxend; kx++)
-                {
-                    m2inv[kx] = 1.0/m2[kx];
-                }
-                for(kx=kxstart; kx<kxend; kx++)
-                {
-                    denom[kx] = 1.0/denom[kx];
-                }
+            calc_exponentials(kxstart,kxend,elfac,denom,tmp1,eterm);
 
-                CALC_EXPONENTIALS(kxstart,kxend,tmp1);
+            for(kx=kxstart; kx<kxend; kx++,p0++)
+            {
+                d1      = p0->re;
+                d2      = p0->im;
 
-                for(kx=kxstart; kx<kxend; kx++,p0++)
-                {
-                    d1      = p0->re;
-                    d2      = p0->im;
-                    
-                    eterm    = ONE_4PI_EPS0/pme->epsilon_r*tmp1[kx]*denom[kx];
-                    
-                    p0->re  = d1*eterm;
-                    p0->im  = d2*eterm;
-                    
-                    struct2 = 2.0*(d1*d1+d2*d2);
-                    
-                    tmp1[kx] = eterm*struct2;
-                }
-                
-                for(kx=kxstart; kx<kxend; kx++)
-                {
-                    ets2     = corner_fac*tmp1[kx];
-                    vfactor  = (factor*m2[kx] + 1.0)*2.0*m2inv[kx];
-                    energy  += ets2;
-                    
-                    ets2vf   = ets2*vfactor;
-                    virxx   += ets2vf*mhx[kx]*mhx[kx] - ets2;
-                    virxy   += ets2vf*mhx[kx]*mhy[kx];
-                    virxz   += ets2vf*mhx[kx]*mhz[kx];
-                    viryy   += ets2vf*mhy[kx]*mhy[kx] - ets2;
-                    viryz   += ets2vf*mhy[kx]*mhz[kx];
-                    virzz   += ets2vf*mhz[kx]*mhz[kx] - ets2;
-                }
+                p0->re  = d1*eterm[kx];
+                p0->im  = d2*eterm[kx];
+
+                struct2 = 2.0*(d1*d1+d2*d2);
+
+                tmp1[kx] = eterm[kx]*struct2;
             }
-            else
+
+            for(kx=kxstart; kx<kxend; kx++)
             {
-                /* We don't need to calculate the energy and the virial.
-                 * In this case the triclinic overhead is small.
-                 */
+                ets2     = corner_fac*tmp1[kx];
+                vfactor  = (factor*m2[kx] + 1.0)*2.0*m2inv[kx];
+                energy  += ets2;
+
+                ets2vf   = ets2*vfactor;
+                virxx   += ets2vf*mhx[kx]*mhx[kx] - ets2;
+                virxy   += ets2vf*mhx[kx]*mhy[kx];
+                virxz   += ets2vf*mhx[kx]*mhz[kx];
+                viryy   += ets2vf*mhy[kx]*mhy[kx] - ets2;
+                viryz   += ets2vf*mhy[kx]*mhz[kx];
+                virzz   += ets2vf*mhz[kx]*mhz[kx] - ets2;
+            }
+        }
+        else
+        {
+            /* We don't need to calculate the energy and the virial.
+             * In this case the triclinic overhead is small.
+             */
 
-                /* Two explicit loops to avoid a conditional inside the loop */
+            /* Two explicit loops to avoid a conditional inside the loop */
 
-                for(kx=kxstart; kx<maxkx; kx++)
-                {
-                    mx = kx;
-                    
-                    mhxk      = mx * rxx;
-                    mhyk      = mx * ryx + my * ryy;
-                    mhzk      = mx * rzx + my * rzy + mz * rzz;
-                    m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
-                    denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
-                    tmp1[kx]  = -factor*m2k;
-                }
-                
-                for(kx=maxkx; kx<kxend; kx++)
-                {
-                    mx = (kx - nx);
-                    
-                    mhxk      = mx * rxx;
-                    mhyk      = mx * ryx + my * ryy;
-                    mhzk      = mx * rzx + my * rzy + mz * rzz;
-                    m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
-                    denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
-                    tmp1[kx]  = -factor*m2k;
-                }
-                
-                for(kx=kxstart; kx<kxend; kx++)
-                {
-                    denom[kx] = 1.0/denom[kx];
-                }
+            for(kx=kxstart; kx<maxkx; kx++)
+            {
+                mx = kx;
+
+                mhxk      = mx * rxx;
+                mhyk      = mx * ryx + my * ryy;
+                mhzk      = mx * rzx + my * rzy + mz * rzz;
+                m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
+                denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
+                tmp1[kx]  = -factor*m2k;
+            }
 
-                CALC_EXPONENTIALS(kxstart,kxend,tmp1);
-               
-                for(kx=kxstart; kx<kxend; kx++,p0++)
-                {
-                    d1      = p0->re;
-                    d2      = p0->im;
-                    
-                    eterm    = ONE_4PI_EPS0/pme->epsilon_r*tmp1[kx]*denom[kx];
-                    
-                    p0->re  = d1*eterm;
-                    p0->im  = d2*eterm;
-                }
+            for(kx=maxkx; kx<kxend; kx++)
+            {
+                mx = (kx - nx);
+
+                mhxk      = mx * rxx;
+                mhyk      = mx * ryx + my * ryy;
+                mhzk      = mx * rzx + my * rzy + mz * rzz;
+                m2k       = mhxk*mhxk + mhyk*mhyk + mhzk*mhzk;
+                denom[kx] = m2k*bz*by*pme->bsp_mod[XX][kx];
+                tmp1[kx]  = -factor*m2k;
+            }
+
+            calc_exponentials(kxstart,kxend,elfac,denom,tmp1,eterm);
+
+            for(kx=kxstart; kx<kxend; kx++,p0++)
+            {
+                d1      = p0->re;
+                d2      = p0->im;
+
+                p0->re  = d1*eterm[kx];
+                p0->im  = d2*eterm[kx];
             }
         }
     }
-    
+
     if (bEnerVir)
     {
         /* Update virial with local values.
@@ -1407,38 +2086,55 @@ static int solve_pme_yzx(gmx_pme_t pme,t_complex *grid,
          * experiencing problems on semiisotropic membranes.
          * IS THAT COMMENT STILL VALID??? (DvdS, 2001/02/07).
          */
-        vir[XX][XX] = 0.25*virxx;
-        vir[YY][YY] = 0.25*viryy;
-        vir[ZZ][ZZ] = 0.25*virzz;
-        vir[XX][YY] = vir[YY][XX] = 0.25*virxy;
-        vir[XX][ZZ] = vir[ZZ][XX] = 0.25*virxz;
-        vir[YY][ZZ] = vir[ZZ][YY] = 0.25*viryz;
-        
+        work->vir[XX][XX] = 0.25*virxx;
+        work->vir[YY][YY] = 0.25*viryy;
+        work->vir[ZZ][ZZ] = 0.25*virzz;
+        work->vir[XX][YY] = work->vir[YY][XX] = 0.25*virxy;
+        work->vir[XX][ZZ] = work->vir[ZZ][XX] = 0.25*virxz;
+        work->vir[YY][ZZ] = work->vir[ZZ][YY] = 0.25*viryz;
+
         /* This energy should be corrected for a charged system */
-        *mesh_energy = 0.5*energy;
+        work->energy = 0.5*energy;
     }
 
     /* Return the loop count */
-    return local_ndata[YY]*local_ndata[ZZ]*local_ndata[XX];
+    return local_ndata[YY]*local_ndata[XX];
 }
 
+static void get_pme_ener_vir(const gmx_pme_t pme,int nthread,
+                             real *mesh_energy,matrix vir)
+{
+    /* This function sums output over threads
+     * and should therefore only be called after thread synchronization.
+     */
+    int thread;
+
+    *mesh_energy = pme->work[0].energy;
+    copy_mat(pme->work[0].vir,vir);
+
+    for(thread=1; thread<nthread; thread++)
+    {
+        *mesh_energy += pme->work[thread].energy;
+        m_add(vir,pme->work[thread].vir,vir);
+    }
+}
 
 #define DO_FSPLINE(order)                      \
 for(ithx=0; (ithx<order); ithx++)              \
-{                                                                         \
+{                                              \
     index_x = (i0+ithx)*pny*pnz;               \
     tx      = thx[ithx];                       \
     dx      = dthx[ithx];                      \
                                                \
     for(ithy=0; (ithy<order); ithy++)          \
-    {                                                                             \
+    {                                          \
         index_xy = index_x+(j0+ithy)*pnz;      \
         ty       = thy[ithy];                  \
         dy       = dthy[ithy];                 \
         fxy1     = fz1 = 0;                    \
                                                \
         for(ithz=0; (ithz<order); ithz++)      \
-        {                                                                 \
+        {                                      \
             gval  = grid[index_xy+(k0+ithz)];  \
             fxy1 += thz[ithz]*gval;            \
             fz1  += dthz[ithz]*gval;           \
@@ -1450,10 +2146,12 @@ for(ithx=0; (ithx<order); ithx++)              \
 }
 
 
-void gather_f_bsplines(gmx_pme_t pme,real *grid,
-                       gmx_bool bClearF,pme_atomcomm_t *atc,real scale)
+static void gather_f_bsplines(gmx_pme_t pme,real *grid,
+                              gmx_bool bClearF,pme_atomcomm_t *atc,
+                              splinedata_t *spline,
+                              real scale)
 {
-    /* sum forces for local particles */  
+    /* sum forces for local particles */
     int     nn,n,ithx,ithy,ithz,i0,j0,k0;
     int     index_x,index_xy;
     int     nx,ny,nz,pnx,pny,pnz;
@@ -1465,21 +2163,25 @@ void gather_f_bsplines(gmx_pme_t pme,real *grid,
     int     norder;
     real    rxx,ryx,ryy,rzx,rzy,rzz;
     int     order;
-    
+
+    pme_spline_work_t *work;
+
+    work = pme->spline_work;
+
     order = pme->pme_order;
-    thx   = atc->theta[XX];
-    thy   = atc->theta[YY];
-    thz   = atc->theta[ZZ];
-    dthx  = atc->dtheta[XX];
-    dthy  = atc->dtheta[YY];
-    dthz  = atc->dtheta[ZZ];
+    thx   = spline->theta[XX];
+    thy   = spline->theta[YY];
+    thz   = spline->theta[ZZ];
+    dthx  = spline->dtheta[XX];
+    dthy  = spline->dtheta[YY];
+    dthz  = spline->dtheta[ZZ];
     nx    = pme->nkx;
     ny    = pme->nky;
     nz    = pme->nkz;
     pnx   = pme->pmegrid_nx;
     pny   = pme->pmegrid_ny;
     pnz   = pme->pmegrid_nz;
-    
+
     rxx   = pme->recipbox[XX][XX];
     ryx   = pme->recipbox[YY][XX];
     ryy   = pme->recipbox[YY][YY];
@@ -1487,41 +2189,63 @@ void gather_f_bsplines(gmx_pme_t pme,real *grid,
     rzy   = pme->recipbox[ZZ][YY];
     rzz   = pme->recipbox[ZZ][ZZ];
 
-    for(nn=0; (nn<atc->n); nn++) 
+    for(nn=0; nn<spline->n; nn++)
     {
-        n = nn;
-        qn      = scale*atc->q[n];
-        
-        if (bClearF) 
+        n  = spline->ind[nn];
+        qn = scale*atc->q[n];
+
+        if (bClearF)
         {
             atc->f[n][XX] = 0;
             atc->f[n][YY] = 0;
             atc->f[n][ZZ] = 0;
         }
-        if (qn != 0) 
+        if (qn != 0)
         {
             fx     = 0;
             fy     = 0;
             fz     = 0;
             idxptr = atc->idx[n];
-            norder = n*order;
-            
-            i0   = idxptr[XX]; 
+            norder = nn*order;
+
+            i0   = idxptr[XX];
             j0   = idxptr[YY];
             k0   = idxptr[ZZ];
-            
+
             /* Pointer arithmetic alert, next six statements */
-            thx  = atc->theta[XX] + norder;
-            thy  = atc->theta[YY] + norder;
-            thz  = atc->theta[ZZ] + norder;
-            dthx = atc->dtheta[XX] + norder;
-            dthy = atc->dtheta[YY] + norder;
-            dthz = atc->dtheta[ZZ] + norder;
-            
+            thx  = spline->theta[XX] + norder;
+            thy  = spline->theta[YY] + norder;
+            thz  = spline->theta[ZZ] + norder;
+            dthx = spline->dtheta[XX] + norder;
+            dthy = spline->dtheta[YY] + norder;
+            dthz = spline->dtheta[ZZ] + norder;
+
             switch (order) {
-            case 4:  DO_FSPLINE(4);     break;
-            case 5:  DO_FSPLINE(5);     break;
-            default: DO_FSPLINE(order); break;
+            case 4:
+#ifdef PME_SSE
+#ifdef PME_SSE_UNALIGNED
+#define PME_GATHER_F_SSE_ORDER4
+#else
+#define PME_GATHER_F_SSE_ALIGNED
+#define PME_ORDER 4
+#endif
+#include "pme_sse_single.h"
+#else
+                DO_FSPLINE(4);
+#endif
+                break;
+            case 5:
+#ifdef PME_SSE
+#define PME_GATHER_F_SSE_ALIGNED
+#define PME_ORDER 5
+#include "pme_sse_single.h"
+#else
+                DO_FSPLINE(5);
+#endif
+                break;
+            default:
+                DO_FSPLINE(order);
+                break;
             }
 
             atc->f[n][XX] += -qn*( fx*nx*rxx );
@@ -1540,9 +2264,11 @@ void gather_f_bsplines(gmx_pme_t pme,real *grid,
      */
 }
 
+
 static real gather_energy_bsplines(gmx_pme_t pme,real *grid,
                                    pme_atomcomm_t *atc)
 {
+    splinedata_t *spline;
     int     n,ithx,ithy,ithz,i0,j0,k0;
     int     index_x,index_xy;
     int *   idxptr;
@@ -1550,26 +2276,27 @@ static real gather_energy_bsplines(gmx_pme_t pme,real *grid,
     real    *thx,*thy,*thz;
     int     norder;
     int     order;
-    
-    
+
+    spline = &atc->spline[0];
+
     order = pme->pme_order;
-    
+
     energy = 0;
     for(n=0; (n<atc->n); n++) {
         qn      = atc->q[n];
-        
+
         if (qn != 0) {
             idxptr = atc->idx[n];
             norder = n*order;
-            
-            i0   = idxptr[XX]; 
+
+            i0   = idxptr[XX];
             j0   = idxptr[YY];
             k0   = idxptr[ZZ];
-            
+
             /* Pointer arithmetic alert, next three statements */
-            thx  = atc->theta[XX] + norder;
-            thy  = atc->theta[YY] + norder;
-            thz  = atc->theta[ZZ] + norder;
+            thx  = spline->theta[XX] + norder;
+            thy  = spline->theta[YY] + norder;
+            thz  = spline->theta[ZZ] + norder;
 
             pot = 0;
             for(ithx=0; (ithx<order); ithx++)
@@ -1598,54 +2325,81 @@ static real gather_energy_bsplines(gmx_pme_t pme,real *grid,
     return energy;
 }
 
+/* Macro to force loop unrolling by fixing order.
+ * This gives a significant performance gain.
+ */
+#define CALC_SPLINE(order)                     \
+{                                              \
+    int j,k,l;                                 \
+    real dr,div;                               \
+    real data[PME_ORDER_MAX];                  \
+    real ddata[PME_ORDER_MAX];                 \
+                                               \
+    for(j=0; (j<DIM); j++)                     \
+    {                                          \
+        dr  = xptr[j];                         \
+                                               \
+        /* dr is relative offset from lower cell limit */ \
+        data[order-1] = 0;                     \
+        data[1] = dr;                          \
+        data[0] = 1 - dr;                      \
+                                               \
+        for(k=3; (k<order); k++)               \
+        {                                      \
+            div = 1.0/(k - 1.0);               \
+            data[k-1] = div*dr*data[k-2];      \
+            for(l=1; (l<(k-1)); l++)           \
+            {                                  \
+                data[k-l-1] = div*((dr+l)*data[k-l-2]+(k-l-dr)* \
+                                   data[k-l-1]);                \
+            }                                  \
+            data[0] = div*(1-dr)*data[0];      \
+        }                                      \
+        /* differentiate */                    \
+        ddata[0] = -data[0];                   \
+        for(k=1; (k<order); k++)               \
+        {                                      \
+            ddata[k] = data[k-1] - data[k];    \
+        }                                      \
+                                               \
+        div = 1.0/(order - 1);                 \
+        data[order-1] = div*dr*data[order-2];  \
+        for(l=1; (l<(order-1)); l++)           \
+        {                                      \
+            data[order-l-1] = div*((dr+l)*data[order-l-2]+    \
+                               (order-l-dr)*data[order-l-1]); \
+        }                                      \
+        data[0] = div*(1 - dr)*data[0];        \
+                                               \
+        for(k=0; k<order; k++)                 \
+        {                                      \
+            theta[j][i*order+k]  = data[k];    \
+            dtheta[j][i*order+k] = ddata[k];   \
+        }                                      \
+    }                                          \
+}
+
 void make_bsplines(splinevec theta,splinevec dtheta,int order,
-                   rvec fractx[],int nr,real charge[],
+                   rvec fractx[],int nr,int ind[],real charge[],
                    gmx_bool bFreeEnergy)
 {
     /* construct splines for local atoms */
-    int  i,j,k,l;
-    real dr,div;
-    real *data,*ddata,*xptr;
-    
-    for(i=0; (i<nr); i++) {
+    int  i,ii;
+    real *xptr;
+
+    for(i=0; i<nr; i++)
+    {
         /* With free energy we do not use the charge check.
          * In most cases this will be more efficient than calling make_bsplines
          * twice, since usually more than half the particles have charges.
          */
-        if (bFreeEnergy || charge[i] != 0.0) {
-            xptr = fractx[i];
-            for(j=0; (j<DIM); j++) {
-                dr  = xptr[j];
-                
-                /* dr is relative offset from lower cell limit */
-                data=&(theta[j][i*order]);
-                data[order-1]=0;
-                data[1]=dr;
-                data[0]=1-dr;
-                
-                for(k=3; (k<order); k++) {
-                    div=1.0/(k-1.0);    
-                    data[k-1]=div*dr*data[k-2];
-                    for(l=1; (l<(k-1)); l++) {
-                        data[k-l-1]=div*((dr+l)*data[k-l-2]+(k-l-dr)*
-                                         data[k-l-1]);
-                    }
-                    data[0]=div*(1-dr)*data[0];
-                }
-                /* differentiate */
-                ddata    = &(dtheta[j][i*order]);
-                ddata[0] = -data[0];
-                for(k=1; (k<order); k++) {
-                    ddata[k]=data[k-1]-data[k];
-                }
-                
-                div=1.0/(order-1);
-                data[order-1]=div*dr*data[order-2];
-                for(l=1; (l<(order-1)); l++) {
-                    data[order-l-1]=div*((dr+l)*data[order-l-2]+
-                                         (order-l-dr)*data[order-l-1]);
-                }
-                data[0]=div*(1-dr)*data[0]; 
+        ii = ind[i];
+        if (bFreeEnergy || charge[ii] != 0.0) {
+            xptr = fractx[ii];
+            switch(order) {
+            case 4:  CALC_SPLINE(4);     break;
+            case 5:  CALC_SPLINE(5);     break;
+            default: CALC_SPLINE(order); break;
             }
         }
     }
@@ -1656,7 +2410,7 @@ void make_dft_mod(real *mod,real *data,int ndata)
 {
   int i,j;
   real sc,ss,arg;
-    
+
   for(i=0;i<ndata;i++) {
     sc=ss=0;
     for(j=0;j<ndata;j++) {
@@ -1672,14 +2426,14 @@ void make_dft_mod(real *mod,real *data,int ndata)
 }
 
 
-
-void make_bspline_moduli(splinevec bsp_mod,int nx,int ny,int nz,int order)
+static void make_bspline_moduli(splinevec bsp_mod,
+                                int nx,int ny,int nz,int order)
 {
   int nmax=max(nx,max(ny,nz));
   real *data,*ddata,*bsp_data;
   int i,k,l;
   real div;
-    
+
   snew(data,order);
   snew(ddata,order);
   snew(bsp_data,nmax);
@@ -1687,7 +2441,7 @@ void make_bspline_moduli(splinevec bsp_mod,int nx,int ny,int nz,int order)
   data[order-1]=0;
   data[1]=0;
   data[0]=1;
-           
+
   for(k=3;k<order;k++) {
     div=1.0/(k-1.0);
     data[k-1]=0;
@@ -1703,13 +2457,13 @@ void make_bspline_moduli(splinevec bsp_mod,int nx,int ny,int nz,int order)
   data[order-1]=0;
   for(l=1;l<(order-1);l++)
     data[order-l-1]=div*(l*data[order-l-2]+(order-l)*data[order-l-1]);
-  data[0]=div*data[0]; 
+  data[0]=div*data[0];
 
   for(i=0;i<nmax;i++)
     bsp_data[i]=0;
   for(i=1;i<=order;i++)
     bsp_data[i]=data[i-1];
-    
+
   make_dft_mod(bsp_mod[XX],bsp_data,nx);
   make_dft_mod(bsp_mod[YY],bsp_data,ny);
   make_dft_mod(bsp_mod[ZZ],bsp_data,nz);
@@ -1719,22 +2473,103 @@ void make_bspline_moduli(splinevec bsp_mod,int nx,int ny,int nz,int order)
   sfree(bsp_data);
 }
 
-static void setup_coordinate_communication(pme_atomcomm_t *atc)
+
+/* Return the P3M optimal influence function */
+static double do_p3m_influence(double z, int order)
 {
-  int nslab,n,i;
-  int fw,bw;
+    double z2,z4;
 
-  nslab = atc->nslab;
+    z2 = z*z;
+    z4 = z2*z2;
 
-  n = 0;
-  for(i=1; i<=nslab/2; i++) {
-    fw = (atc->nodeid + i) % nslab;
-    bw = (atc->nodeid - i + nslab) % nslab;
-    if (n < nslab - 1) {
-      atc->node_dest[n] = fw;
-      atc->node_src[n]  = bw;
-      n++;
-    } 
+    /* The formula and most constants can be found in:
+     * Ballenegger et al., JCTC 8, 936 (2012)
+     */
+    switch(order)
+    {
+    case 2:
+        return 1.0 - 2.0*z2/3.0;
+        break;
+    case 3:
+        return 1.0 - z2 + 2.0*z4/15.0;
+        break;
+    case 4:
+        return 1.0 - 4.0*z2/3.0 + 2.0*z4/5.0 + 4.0*z2*z4/315.0;
+        break;
+    case 5:
+        return 1.0 - 5.0*z2/3.0 + 7.0*z4/9.0 - 17.0*z2*z4/189.0 + 2.0*z4*z4/2835.0;
+        break;
+    case 6:
+        return 1.0 - 2.0*z2 + 19.0*z4/15.0 - 256.0*z2*z4/945.0 + 62.0*z4*z4/4725.0 + 4.0*z2*z4*z4/155925.0;
+        break;
+    case 7:
+        return 1.0 - 7.0*z2/3.0 + 28.0*z4/15.0 - 16.0*z2*z4/27.0 + 26.0*z4*z4/405.0 - 2.0*z2*z4*z4/1485.0 + 4.0*z4*z4*z4/6081075.0;
+    case 8:
+        return 1.0 - 8.0*z2/3.0 + 116.0*z4/45.0 - 344.0*z2*z4/315.0 + 914.0*z4*z4/4725.0 - 248.0*z4*z4*z2/22275.0 + 21844.0*z4*z4*z4/212837625.0 - 8.0*z4*z4*z4*z2/638512875.0;
+        break;
+    }
+
+    return 0.0;
+}
+
+/* Calculate the P3M B-spline moduli for one dimension */
+static void make_p3m_bspline_moduli_dim(real *bsp_mod,int n,int order)
+{
+    double zarg,zai,sinzai,infl;
+    int    maxk,i;
+
+    if (order > 8)
+    {
+        gmx_fatal(FARGS,"The current P3M code only supports orders up to 8");
+    }
+
+    zarg = M_PI/n;
+
+    maxk = (n + 1)/2;
+
+    for(i=-maxk; i<0; i++)
+    {
+        zai    = zarg*i;
+        sinzai = sin(zai);
+        infl   = do_p3m_influence(sinzai,order);
+        bsp_mod[n+i] = infl*infl*pow(sinzai/zai,-2.0*order);
+    }
+    bsp_mod[0] = 1.0;
+    for(i=1; i<maxk; i++)
+    {
+        zai    = zarg*i;
+        sinzai = sin(zai);
+        infl   = do_p3m_influence(sinzai,order);
+        bsp_mod[i] = infl*infl*pow(sinzai/zai,-2.0*order);
+    }
+}
+
+/* Calculate the P3M B-spline moduli */
+static void make_p3m_bspline_moduli(splinevec bsp_mod,
+                                    int nx,int ny,int nz,int order)
+{
+    make_p3m_bspline_moduli_dim(bsp_mod[XX],nx,order);
+    make_p3m_bspline_moduli_dim(bsp_mod[YY],ny,order);
+    make_p3m_bspline_moduli_dim(bsp_mod[ZZ],nz,order);
+}
+
+
+static void setup_coordinate_communication(pme_atomcomm_t *atc)
+{
+  int nslab,n,i;
+  int fw,bw;
+
+  nslab = atc->nslab;
+
+  n = 0;
+  for(i=1; i<=nslab/2; i++) {
+    fw = (atc->nodeid + i) % nslab;
+    bw = (atc->nodeid - i + nslab) % nslab;
+    if (n < nslab - 1) {
+      atc->node_dest[n] = fw;
+      atc->node_src[n]  = bw;
+      n++;
+    }
     if (n < nslab - 1) {
       atc->node_dest[n] = bw;
       atc->node_src[n]  = fw;
@@ -1745,6 +2580,8 @@ static void setup_coordinate_communication(pme_atomcomm_t *atc)
 
 int gmx_pme_destroy(FILE *log,gmx_pme_t *pmedata)
 {
+    int thread;
+
     if(NULL != log)
     {
         fprintf(log,"Destroying PME data structures.\n");
@@ -1753,28 +2590,29 @@ int gmx_pme_destroy(FILE *log,gmx_pme_t *pmedata)
     sfree((*pmedata)->nnx);
     sfree((*pmedata)->nny);
     sfree((*pmedata)->nnz);
-       
-    sfree((*pmedata)->pmegridA);
+
+    pmegrids_destroy(&(*pmedata)->pmegridA);
+
     sfree((*pmedata)->fftgridA);
     sfree((*pmedata)->cfftgridA);
     gmx_parallel_3dfft_destroy((*pmedata)->pfft_setupA);
-    
-    if((*pmedata)->pmegridB)
+
+    if ((*pmedata)->pmegridB.grid.grid != NULL)
     {
-        sfree((*pmedata)->pmegridB);
+        pmegrids_destroy(&(*pmedata)->pmegridB);
         sfree((*pmedata)->fftgridB);
         sfree((*pmedata)->cfftgridB);
         gmx_parallel_3dfft_destroy((*pmedata)->pfft_setupB);
     }
-    sfree((*pmedata)->work_mhz);
-    sfree((*pmedata)->work_m2);
-    sfree((*pmedata)->work_denom);
-    sfree((*pmedata)->work_tmp1_alloc);
-    sfree((*pmedata)->work_m2inv);
-       
+    for(thread=0; thread<(*pmedata)->nthread; thread++)
+    {
+        free_work(&(*pmedata)->work[thread]);
+    }
+    sfree((*pmedata)->work);
+
     sfree(*pmedata);
     *pmedata = NULL;
-  
+
   return 0;
 }
 
@@ -1804,7 +2642,7 @@ static double pme_load_imbalance(gmx_pme_t pme)
 static void init_atomcomm(gmx_pme_t pme,pme_atomcomm_t *atc, t_commrec *cr,
                           int dimind,gmx_bool bSpread)
 {
-    int nk,k,s;
+    int nk,k,s,thread;
 
     atc->dimind = dimind;
     atc->nslab  = 1;
@@ -1832,22 +2670,43 @@ static void init_atomcomm(gmx_pme_t pme,pme_atomcomm_t *atc, t_commrec *cr,
         snew(atc->node_dest,atc->nslab);
         snew(atc->node_src,atc->nslab);
         setup_coordinate_communication(atc);
-        
-        snew(atc->count,atc->nslab);
+
+        snew(atc->count_thread,pme->nthread);
+        for(thread=0; thread<pme->nthread; thread++)
+        {
+            snew(atc->count_thread[thread],atc->nslab);
+        }
+        atc->count = atc->count_thread[0];
         snew(atc->rcount,atc->nslab);
         snew(atc->buf_index,atc->nslab);
     }
+
+    atc->nthread = pme->nthread;
+    if (atc->nthread > 1)
+    {
+        snew(atc->thread_plist,atc->nthread);
+    }
+    snew(atc->spline,atc->nthread);
+    for(thread=0; thread<atc->nthread; thread++)
+    {
+        if (atc->nthread > 1)
+        {
+            snew(atc->thread_plist[thread].n,atc->nthread+2*GMX_CACHE_SEP);
+            atc->thread_plist[thread].n += GMX_CACHE_SEP;
+        }
+    }
 }
 
-static void 
+static void
 init_overlap_comm(pme_overlap_t *  ol,
                   int              norder,
 #ifdef GMX_MPI
-                  MPI_Comm         comm,  
+                  MPI_Comm         comm,
 #endif
-                  int              nnodes, 
+                  int              nnodes,
                   int              nodeid,
-                  int              ndata)
+                  int              ndata,
+                  int              commplainsize)
 {
     int lbnd,rbnd,maxlr,b,i;
     int exten;
@@ -1855,11 +2714,11 @@ init_overlap_comm(pme_overlap_t *  ol,
     pme_grid_comm_t *pgc;
     gmx_bool bCont;
     int fft_start,fft_end,send_index1,recv_index1;
-    
+
 #ifdef GMX_MPI
     ol->mpi_comm = comm;
 #endif
-    
+
     ol->nnodes = nnodes;
     ol->nodeid = nodeid;
 
@@ -1873,7 +2732,7 @@ init_overlap_comm(pme_overlap_t *  ol,
     snew(ol->s2g0,ol->nnodes+1);
     snew(ol->s2g1,ol->nnodes);
     if (debug) { fprintf(debug,"PME slab boundaries:"); }
-    for(i=0; i<nnodes; i++) 
+    for(i=0; i<nnodes; i++)
     {
         /* s2g0 the local interpolation grid start.
          * s2g1 the local interpolation grid end.
@@ -1946,6 +2805,10 @@ init_overlap_comm(pme_overlap_t *  ol,
         pgc->recv_index0 = fft_start;
         pgc->recv_nindex = max(0,recv_index1 - pgc->recv_index0);
     }
+
+    /* For non-divisible grid we need pme_order iso pme_order-1 */
+    snew(ol->sendbuf,norder*commplainsize);
+    snew(ol->recvbuf,norder*commplainsize);
 }
 
 static void
@@ -1985,7 +2848,7 @@ make_gridindex5_to_localindex(int n,int local_start,int local_range,
                 if (gtl[i] == n-1)
                 {
                     gtl[i] = 0;
-                    fsh[i] = -1; 
+                    fsh[i] = -1;
                 }
                 else if (gtl[i] == local_range)
                 {
@@ -2000,6 +2863,41 @@ make_gridindex5_to_localindex(int n,int local_start,int local_range,
     *fraction_shift  = fsh;
 }
 
+static pme_spline_work_t *make_pme_spline_work(int order)
+{
+    pme_spline_work_t *work;
+
+#ifdef PME_SSE
+    float  tmp[8];
+    __m128 zero_SSE;
+    int    of,i;
+
+    snew_aligned(work,1,16);
+
+    zero_SSE = _mm_setzero_ps();
+
+    /* Generate bit masks to mask out the unused grid entries,
+     * as we only operate on order of the 8 grid entries that are
+     * load into 2 SSE float registers.
+     */
+    for(of=0; of<8-(order-1); of++)
+    {
+        for(i=0; i<8; i++)
+        {
+            tmp[i] = (i >= of && i < of+order ? 1 : 0);
+        }
+        work->mask_SSE0[of] = _mm_loadu_ps(tmp);
+        work->mask_SSE1[of] = _mm_loadu_ps(tmp+4);
+        work->mask_SSE0[of] = _mm_cmpgt_ps(work->mask_SSE0[of],zero_SSE);
+        work->mask_SSE1[of] = _mm_cmpgt_ps(work->mask_SSE1[of],zero_SSE);
+    }
+#else
+    work = NULL;
+#endif
+
+    return work;
+}
+
 static void
 gmx_pme_check_grid_restrictions(FILE *fplog,char dim,int nnodes,int *nk)
 {
@@ -2014,13 +2912,13 @@ gmx_pme_check_grid_restrictions(FILE *fplog,char dim,int nnodes,int *nk)
             gmx_fatal(FARGS,"The PME grid size in dim %c (%d) is not divisble by the number of nodes doing PME in dim %c (%d). The grid size would have to be increased by more than 50%% to make the grid divisible. Change the total number of nodes or the number of domain decomposition cells in x or the PME grid %c dimension (and the cut-off).",
                       dim,*nk,dim,nnodes,dim);
         }
-        
+
         if (fplog != NULL)
         {
             fprintf(fplog,"\nNOTE: The PME grid size in dim %c (%d) is not divisble by the number of nodes doing PME in dim %c (%d). Increasing the PME grid size in dim %c to %d. This will increase the accuracy and will not decrease the performance significantly on this number of nodes. For optimal performance change the total number of nodes or the number of domain decomposition cells in x or the PME grid %c dimension (and the cut-off).\n\n",
                     dim,*nk,dim,nnodes,dim,nk_new,dim);
         }
-            
+
         *nk = nk_new;
     }
 }
@@ -2031,36 +2929,36 @@ int gmx_pme_init(gmx_pme_t *         pmedata,
                  int                 nnodes_minor,
                  t_inputrec *        ir,
                  int                 homenr,
-                 gmx_bool                bFreeEnergy,
-                 gmx_bool                bReproducible)
+                 gmx_bool            bFreeEnergy,
+                 gmx_bool            bReproducible,
+                 int                 nthread)
 {
     gmx_pme_t pme=NULL;
-    
+
     pme_atomcomm_t *atc;
-    int bufsizex,bufsizey,bufsize;
     ivec ndata;
-    
+
     if (debug)
         fprintf(debug,"Creating PME data structures.\n");
     snew(pme,1);
-        
+
     pme->redist_init         = FALSE;
     pme->sum_qgrid_tmp       = NULL;
     pme->sum_qgrid_dd_tmp    = NULL;
     pme->buf_nalloc          = 0;
     pme->redist_buf_nalloc   = 0;
-    
+
     pme->nnodes              = 1;
     pme->bPPnode             = TRUE;
-    
+
     pme->nnodes_major        = nnodes_major;
     pme->nnodes_minor        = nnodes_minor;
 
 #ifdef GMX_MPI
-    if (nnodes_major*nnodes_minor > 1 && PAR(cr)) 
+    if (nnodes_major*nnodes_minor > 1)
     {
         pme->mpi_comm = cr->mpi_comm_mygroup;
-        
+
         MPI_Comm_rank(pme->mpi_comm,&pme->nodeid);
         MPI_Comm_size(pme->mpi_comm,&pme->nnodes);
         if (pme->nnodes != nnodes_major*nnodes_minor)
@@ -2083,6 +2981,9 @@ int gmx_pme_init(gmx_pme_t *         pmedata,
         pme->ndecompdim = 0;
         pme->nodeid_major = 0;
         pme->nodeid_minor = 0;
+#ifdef GMX_MPI
+        pme->mpi_comm_d[0] = pme->mpi_comm_d[1] = MPI_COMM_NULL;
+#endif
     }
     else
     {
@@ -2095,7 +2996,7 @@ int gmx_pme_init(gmx_pme_t *         pmedata,
             pme->ndecompdim = 1;
             pme->nodeid_major = pme->nodeid;
             pme->nodeid_minor = 0;
-            
+
         }
         else if (nnodes_major == 1)
         {
@@ -2107,20 +3008,20 @@ int gmx_pme_init(gmx_pme_t *         pmedata,
             pme->nodeid_major = 0;
             pme->nodeid_minor = pme->nodeid;
         }
-        else 
+        else
         {
             if (pme->nnodes % nnodes_major != 0)
             {
                 gmx_incons("For 2D PME decomposition, #PME nodes must be divisible by the number of nodes in the major dimension");
             }
             pme->ndecompdim = 2;
-            
+
 #ifdef GMX_MPI
             MPI_Comm_split(pme->mpi_comm,pme->nodeid % nnodes_minor,
                            pme->nodeid,&pme->mpi_comm_d[0]);  /* My communicator along major dimension */
             MPI_Comm_split(pme->mpi_comm,pme->nodeid/nnodes_minor,
                            pme->nodeid,&pme->mpi_comm_d[1]);  /* My communicator along minor dimension */
-            
+
             MPI_Comm_rank(pme->mpi_comm_d[0],&pme->nodeid_major);
             MPI_Comm_size(pme->mpi_comm_d[0],&pme->nnodes_major);
             MPI_Comm_rank(pme->mpi_comm_d[1],&pme->nodeid_minor);
@@ -2129,19 +3030,28 @@ int gmx_pme_init(gmx_pme_t *         pmedata,
         }
         pme->bPPnode = (cr->duty & DUTY_PP);
     }
-    
+
+    pme->nthread = nthread;
+
     if (ir->ePBC == epbcSCREW)
     {
         gmx_fatal(FARGS,"pme does not (yet) work with pbc = screw");
     }
-    
+
     pme->bFEP        = ((ir->efep != efepNO) && bFreeEnergy);
     pme->nkx         = ir->nkx;
     pme->nky         = ir->nky;
     pme->nkz         = ir->nkz;
+    pme->bP3M        = (ir->coulombtype == eelP3M_AD || getenv("GMX_PME_P3M") != NULL);
     pme->pme_order   = ir->pme_order;
     pme->epsilon_r   = ir->epsilon_r;
-    
+
+    if (pme->pme_order > PME_ORDER_MAX)
+    {
+        gmx_fatal(FARGS,"pme_order (%d) is larger than the maximum allowed value (%d). Modify and recompile the code if you really need such a high order.",
+                  pme->pme_order,PME_ORDER_MAX);
+    }
+
     /* Currently pme.c supports only the fft5d FFT code.
      * Therefore the grid always needs to be divisible by nnodes.
      * When the old 1D code is also supported again, change this check.
@@ -2165,180 +3075,838 @@ int gmx_pme_init(gmx_pme_t *         pmedata,
         pme->nky <= pme->pme_order*(pme->nnodes_minor > 1 ? 2 : 1) ||
         pme->nkz <= pme->pme_order)
     {
-        gmx_fatal(FARGS,"The pme grid dimensions need to be larger than pme_order (%d) and in parallel larger than 2*pme_order for x and/or y",pme->pme_order);
+        gmx_fatal(FARGS,"The pme grid dimensions need to be larger than pme_order (%d) and in parallel larger than 2*pme_ordern for x and/or y",pme->pme_order);
     }
 
     if (pme->nnodes > 1) {
         double imbal;
 
 #ifdef GMX_MPI
-        MPI_Type_contiguous(DIM, mpi_type, &(pme->rvec_mpi));
-        MPI_Type_commit(&(pme->rvec_mpi));
+        MPI_Type_contiguous(DIM, mpi_type, &(pme->rvec_mpi));
+        MPI_Type_commit(&(pme->rvec_mpi));
+#endif
+
+        /* Note that the charge spreading and force gathering, which usually
+         * takes about the same amount of time as FFT+solve_pme,
+         * is always fully load balanced
+         * (unless the charge distribution is inhomogeneous).
+         */
+
+        imbal = pme_load_imbalance(pme);
+        if (imbal >= 1.2 && pme->nodeid_major == 0 && pme->nodeid_minor == 0)
+        {
+            fprintf(stderr,
+                    "\n"
+                    "NOTE: The load imbalance in PME FFT and solve is %d%%.\n"
+                    "      For optimal PME load balancing\n"
+                    "      PME grid_x (%d) and grid_y (%d) should be divisible by #PME_nodes_x (%d)\n"
+                    "      and PME grid_y (%d) and grid_z (%d) should be divisible by #PME_nodes_y (%d)\n"
+                    "\n",
+                    (int)((imbal-1)*100 + 0.5),
+                    pme->nkx,pme->nky,pme->nnodes_major,
+                    pme->nky,pme->nkz,pme->nnodes_minor);
+        }
+    }
+
+    /* For non-divisible grid we need pme_order iso pme_order-1 */
+    /* In sum_qgrid_dd x overlap is copied in place: take padding into account.
+     * y is always copied through a buffer: we don't need padding in z,
+     * but we do need the overlap in x because of the communication order.
+     */
+    init_overlap_comm(&pme->overlap[0],pme->pme_order,
+#ifdef GMX_MPI
+                      pme->mpi_comm_d[0],
+#endif
+                      pme->nnodes_major,pme->nodeid_major,
+                      pme->nkx,
+                      (div_round_up(pme->nky,pme->nnodes_minor)+pme->pme_order)*(pme->nkz+pme->pme_order-1));
+
+    init_overlap_comm(&pme->overlap[1],pme->pme_order,
+#ifdef GMX_MPI
+                      pme->mpi_comm_d[1],
+#endif
+                      pme->nnodes_minor,pme->nodeid_minor,
+                      pme->nky,
+                      (div_round_up(pme->nkx,pme->nnodes_major)+pme->pme_order)*pme->nkz);
+
+    /* Check for a limitation of the (current) sum_fftgrid_dd code */
+    if (pme->nthread > 1 &&
+        (pme->overlap[0].noverlap_nodes > 1 ||
+         pme->overlap[1].noverlap_nodes > 1))
+    {
+        gmx_fatal(FARGS,"With threads the number of grid lines per node along x and or y should be pme_order (%d) or more or exactly pme_order-1",pme->pme_order);
+    }
+
+    snew(pme->bsp_mod[XX],pme->nkx);
+    snew(pme->bsp_mod[YY],pme->nky);
+    snew(pme->bsp_mod[ZZ],pme->nkz);
+
+    /* The required size of the interpolation grid, including overlap.
+     * The allocated size (pmegrid_n?) might be slightly larger.
+     */
+    pme->pmegrid_nx = pme->overlap[0].s2g1[pme->nodeid_major] -
+                      pme->overlap[0].s2g0[pme->nodeid_major];
+    pme->pmegrid_ny = pme->overlap[1].s2g1[pme->nodeid_minor] -
+                      pme->overlap[1].s2g0[pme->nodeid_minor];
+    pme->pmegrid_nz_base = pme->nkz;
+    pme->pmegrid_nz = pme->pmegrid_nz_base + pme->pme_order - 1;
+    set_grid_alignment(&pme->pmegrid_nz,pme->pme_order);
+
+    pme->pmegrid_start_ix = pme->overlap[0].s2g0[pme->nodeid_major];
+    pme->pmegrid_start_iy = pme->overlap[1].s2g0[pme->nodeid_minor];
+    pme->pmegrid_start_iz = 0;
+
+    make_gridindex5_to_localindex(pme->nkx,
+                                  pme->pmegrid_start_ix,
+                                  pme->pmegrid_nx - (pme->pme_order-1),
+                                  &pme->nnx,&pme->fshx);
+    make_gridindex5_to_localindex(pme->nky,
+                                  pme->pmegrid_start_iy,
+                                  pme->pmegrid_ny - (pme->pme_order-1),
+                                  &pme->nny,&pme->fshy);
+    make_gridindex5_to_localindex(pme->nkz,
+                                  pme->pmegrid_start_iz,
+                                  pme->pmegrid_nz_base,
+                                  &pme->nnz,&pme->fshz);
+
+    pmegrids_init(&pme->pmegridA,
+                  pme->pmegrid_nx,pme->pmegrid_ny,pme->pmegrid_nz,
+                  pme->pmegrid_nz_base,
+                  pme->pme_order,
+                  pme->nthread,
+                  pme->overlap[0].s2g1[pme->nodeid_major]-pme->overlap[0].s2g0[pme->nodeid_major+1],
+                  pme->overlap[1].s2g1[pme->nodeid_minor]-pme->overlap[1].s2g0[pme->nodeid_minor+1]);
+
+    pme->spline_work = make_pme_spline_work(pme->pme_order);
+
+    ndata[0] = pme->nkx;
+    ndata[1] = pme->nky;
+    ndata[2] = pme->nkz;
+
+    /* This routine will allocate the grid data to fit the FFTs */
+    gmx_parallel_3dfft_init(&pme->pfft_setupA,ndata,
+                            &pme->fftgridA,&pme->cfftgridA,
+                            pme->mpi_comm_d,
+                            pme->overlap[0].s2g0,pme->overlap[1].s2g0,
+                            bReproducible,pme->nthread);
+
+    if (bFreeEnergy)
+    {
+        pmegrids_init(&pme->pmegridB,
+                      pme->pmegrid_nx,pme->pmegrid_ny,pme->pmegrid_nz,
+                      pme->pmegrid_nz_base,
+                      pme->pme_order,
+                      pme->nthread,
+                      pme->nkx % pme->nnodes_major != 0,
+                      pme->nky % pme->nnodes_minor != 0);
+
+        gmx_parallel_3dfft_init(&pme->pfft_setupB,ndata,
+                                &pme->fftgridB,&pme->cfftgridB,
+                                pme->mpi_comm_d,
+                                pme->overlap[0].s2g0,pme->overlap[1].s2g0,
+                                bReproducible,pme->nthread);
+    }
+    else
+    {
+        pme->pmegridB.grid.grid = NULL;
+        pme->fftgridB           = NULL;
+        pme->cfftgridB          = NULL;
+    }
+
+    if (!pme->bP3M)
+    {
+        /* Use plain SPME B-spline interpolation */
+        make_bspline_moduli(pme->bsp_mod,pme->nkx,pme->nky,pme->nkz,pme->pme_order);
+    }
+    else
+    {
+        /* Use the P3M grid-optimized influence function */
+        make_p3m_bspline_moduli(pme->bsp_mod,pme->nkx,pme->nky,pme->nkz,pme->pme_order);
+    }
+
+    /* Use atc[0] for spreading */
+    init_atomcomm(pme,&pme->atc[0],cr,nnodes_major > 1 ? 0 : 1,TRUE);
+    if (pme->ndecompdim >= 2)
+    {
+        init_atomcomm(pme,&pme->atc[1],cr,1,FALSE);
+    }
+
+    if (pme->nnodes == 1) {
+        pme->atc[0].n = homenr;
+        pme_realloc_atomcomm_things(&pme->atc[0]);
+    }
+
+    {
+        int thread;
+
+        /* Use fft5d, order after FFT is y major, z, x minor */
+
+        snew(pme->work,pme->nthread);
+        for(thread=0; thread<pme->nthread; thread++)
+        {
+            realloc_work(&pme->work[thread],pme->nkx);
+        }
+    }
+
+    *pmedata = pme;
+
+    return 0;
+}
+
+
+static void copy_local_grid(gmx_pme_t pme,
+                            pmegrids_t *pmegrids,int thread,real *fftgrid)
+{
+    ivec local_fft_ndata,local_fft_offset,local_fft_size;
+    int  fft_my,fft_mz;
+    int  nsx,nsy,nsz;
+    ivec nf;
+    int  offx,offy,offz,x,y,z,i0,i0t;
+    int  d;
+    pmegrid_t *pmegrid;
+    real *grid_th;
+
+    gmx_parallel_3dfft_real_limits(pme->pfft_setupA,
+                                   local_fft_ndata,
+                                   local_fft_offset,
+                                   local_fft_size);
+    fft_my = local_fft_size[YY];
+    fft_mz = local_fft_size[ZZ];
+
+    pmegrid = &pmegrids->grid_th[thread];
+
+    nsx = pmegrid->n[XX];
+    nsy = pmegrid->n[YY];
+    nsz = pmegrid->n[ZZ];
+
+    for(d=0; d<DIM; d++)
+    {
+        nf[d] = min(pmegrid->n[d] - (pmegrid->order - 1),
+                    local_fft_ndata[d] - pmegrid->offset[d]);
+    }
+
+    offx = pmegrid->offset[XX];
+    offy = pmegrid->offset[YY];
+    offz = pmegrid->offset[ZZ];
+
+    /* Directly copy the non-overlapping parts of the local grids.
+     * This also initializes the full grid.
+     */
+    grid_th = pmegrid->grid;
+    for(x=0; x<nf[XX]; x++)
+    {
+        for(y=0; y<nf[YY]; y++)
+        {
+            i0  = ((offx + x)*fft_my + (offy + y))*fft_mz + offz;
+            i0t = (x*nsy + y)*nsz;
+            for(z=0; z<nf[ZZ]; z++)
+            {
+                fftgrid[i0+z] = grid_th[i0t+z];
+            }
+        }
+    }
+}
+
+static void print_sendbuf(gmx_pme_t pme,real *sendbuf)
+{
+    ivec local_fft_ndata,local_fft_offset,local_fft_size;
+    pme_overlap_t *overlap;
+    int datasize,nind;
+    int i,x,y,z,n;
+
+    gmx_parallel_3dfft_real_limits(pme->pfft_setupA,
+                                   local_fft_ndata,
+                                   local_fft_offset,
+                                   local_fft_size);
+    /* Major dimension */
+    overlap = &pme->overlap[0];
+
+    nind   = overlap->comm_data[0].send_nindex;
+
+    for(y=0; y<local_fft_ndata[YY]; y++) {
+         printf(" %2d",y);
+    }
+    printf("\n");
+
+    i = 0;
+    for(x=0; x<nind; x++) {
+        for(y=0; y<local_fft_ndata[YY]; y++) {
+            n = 0;
+            for(z=0; z<local_fft_ndata[ZZ]; z++) {
+                if (sendbuf[i] != 0) n++;
+                i++;
+            }
+            printf(" %2d",n);
+        }
+        printf("\n");
+    }
+}
+
+static void
+reduce_threadgrid_overlap(gmx_pme_t pme,
+                          const pmegrids_t *pmegrids,int thread,
+                          real *fftgrid,real *commbuf_x,real *commbuf_y)
+{
+    ivec local_fft_ndata,local_fft_offset,local_fft_size;
+    int  fft_nx,fft_ny,fft_nz;
+    int  fft_my,fft_mz;
+    int  buf_my=-1;
+    int  nsx,nsy,nsz;
+    ivec ne;
+    int  offx,offy,offz,x,y,z,i0,i0t;
+    int  sx,sy,sz,fx,fy,fz,tx1,ty1,tz1,ox,oy,oz;
+    gmx_bool bClearBufX,bClearBufY,bClearBufXY,bClearBuf;
+    gmx_bool bCommX,bCommY;
+    int  d;
+    int  thread_f;
+    const pmegrid_t *pmegrid,*pmegrid_g,*pmegrid_f;
+    const real *grid_th;
+    real *commbuf=NULL;
+
+    gmx_parallel_3dfft_real_limits(pme->pfft_setupA,
+                                   local_fft_ndata,
+                                   local_fft_offset,
+                                   local_fft_size);
+    fft_nx = local_fft_ndata[XX];
+    fft_ny = local_fft_ndata[YY];
+    fft_nz = local_fft_ndata[ZZ];
+
+    fft_my = local_fft_size[YY];
+    fft_mz = local_fft_size[ZZ];
+
+    /* This routine is called when all thread have finished spreading.
+     * Here each thread sums grid contributions calculated by other threads
+     * to the thread local grid volume.
+     * To minimize the number of grid copying operations,
+     * this routines sums immediately from the pmegrid to the fftgrid.
+     */
+
+    /* Determine which part of the full node grid we should operate on,
+     * this is our thread local part of the full grid.
+     */
+    pmegrid = &pmegrids->grid_th[thread];
+
+    for(d=0; d<DIM; d++)
+    {
+        ne[d] = min(pmegrid->offset[d]+pmegrid->n[d]-(pmegrid->order-1),
+                    local_fft_ndata[d]);
+    }
+
+    offx = pmegrid->offset[XX];
+    offy = pmegrid->offset[YY];
+    offz = pmegrid->offset[ZZ];
+
+
+    bClearBufX  = TRUE;
+    bClearBufY  = TRUE;
+    bClearBufXY = TRUE;
+
+    /* Now loop over all the thread data blocks that contribute
+     * to the grid region we (our thread) are operating on.
+     */
+    /* Note that ffy_nx/y is equal to the number of grid points
+     * between the first point of our node grid and the one of the next node.
+     */
+    for(sx=0; sx>=-pmegrids->nthread_comm[XX]; sx--)
+    {
+        fx = pmegrid->ci[XX] + sx;
+        ox = 0;
+        bCommX = FALSE;
+        if (fx < 0) {
+            fx += pmegrids->nc[XX];
+            ox -= fft_nx;
+            bCommX = (pme->nnodes_major > 1);
+        }
+        pmegrid_g = &pmegrids->grid_th[fx*pmegrids->nc[YY]*pmegrids->nc[ZZ]];
+        ox += pmegrid_g->offset[XX];
+        if (!bCommX)
+        {
+            tx1 = min(ox + pmegrid_g->n[XX],ne[XX]);
+        }
+        else
+        {
+            tx1 = min(ox + pmegrid_g->n[XX],pme->pme_order);
+        }
+
+        for(sy=0; sy>=-pmegrids->nthread_comm[YY]; sy--)
+        {
+            fy = pmegrid->ci[YY] + sy;
+            oy = 0;
+            bCommY = FALSE;
+            if (fy < 0) {
+                fy += pmegrids->nc[YY];
+                oy -= fft_ny;
+                bCommY = (pme->nnodes_minor > 1);
+            }
+            pmegrid_g = &pmegrids->grid_th[fy*pmegrids->nc[ZZ]];
+            oy += pmegrid_g->offset[YY];
+            if (!bCommY)
+            {
+                ty1 = min(oy + pmegrid_g->n[YY],ne[YY]);
+            }
+            else
+            {
+                ty1 = min(oy + pmegrid_g->n[YY],pme->pme_order);
+            }
+
+            for(sz=0; sz>=-pmegrids->nthread_comm[ZZ]; sz--)
+            {
+                fz = pmegrid->ci[ZZ] + sz;
+                oz = 0;
+                if (fz < 0)
+                {
+                    fz += pmegrids->nc[ZZ];
+                    oz -= fft_nz;
+                }
+                pmegrid_g = &pmegrids->grid_th[fz];
+                oz += pmegrid_g->offset[ZZ];
+                tz1 = min(oz + pmegrid_g->n[ZZ],ne[ZZ]);
+
+                if (sx == 0 && sy == 0 && sz == 0)
+                {
+                    /* We have already added our local contribution
+                     * before calling this routine, so skip it here.
+                     */
+                    continue;
+                }
+
+                thread_f = (fx*pmegrids->nc[YY] + fy)*pmegrids->nc[ZZ] + fz;
+
+                pmegrid_f = &pmegrids->grid_th[thread_f];
+
+                grid_th = pmegrid_f->grid;
+
+                nsx = pmegrid_f->n[XX];
+                nsy = pmegrid_f->n[YY];
+                nsz = pmegrid_f->n[ZZ];
+
+#ifdef DEBUG_PME_REDUCE
+                printf("n%d t%d add %d  %2d %2d %2d  %2d %2d %2d  %2d-%2d %2d-%2d, %2d-%2d %2d-%2d, %2d-%2d %2d-%2d\n",
+                       pme->nodeid,thread,thread_f,
+                       pme->pmegrid_start_ix,
+                       pme->pmegrid_start_iy,
+                       pme->pmegrid_start_iz,
+                       sx,sy,sz,
+                       offx-ox,tx1-ox,offx,tx1,
+                       offy-oy,ty1-oy,offy,ty1,
+                       offz-oz,tz1-oz,offz,tz1);
+#endif
+
+                if (!(bCommX || bCommY))
+                {
+                    /* Copy from the thread local grid to the node grid */
+                    for(x=offx; x<tx1; x++)
+                    {
+                        for(y=offy; y<ty1; y++)
+                        {
+                            i0  = (x*fft_my + y)*fft_mz;
+                            i0t = ((x - ox)*nsy + (y - oy))*nsz - oz;
+                            for(z=offz; z<tz1; z++)
+                            {
+                                fftgrid[i0+z] += grid_th[i0t+z];
+                            }
+                        }
+                    }
+                }
+                else
+                {
+                    /* The order of this conditional decides
+                     * where the corner volume gets stored with x+y decomp.
+                     */
+                    if (bCommY)
+                    {
+                        commbuf = commbuf_y;
+                        buf_my  = ty1 - offy;
+                        if (bCommX)
+                        {
+                            /* We index commbuf modulo the local grid size */
+                            commbuf += buf_my*fft_nx*fft_nz;
+
+                            bClearBuf  = bClearBufXY;
+                            bClearBufXY = FALSE;
+                        }
+                        else
+                        {
+                            bClearBuf  = bClearBufY;
+                            bClearBufY = FALSE;
+                        }
+                    }
+                    else
+                    {
+                        commbuf = commbuf_x;
+                        buf_my  = fft_ny;
+                        bClearBuf  = bClearBufX;
+                        bClearBufX = FALSE;
+                    }
+
+                    /* Copy to the communication buffer */
+                    for(x=offx; x<tx1; x++)
+                    {
+                        for(y=offy; y<ty1; y++)
+                        {
+                            i0  = (x*buf_my + y)*fft_nz;
+                            i0t = ((x - ox)*nsy + (y - oy))*nsz - oz;
+
+                            if (bClearBuf)
+                            {
+                                /* First access of commbuf, initialize it */
+                                for(z=offz; z<tz1; z++)
+                                {
+                                    commbuf[i0+z]  = grid_th[i0t+z];
+                                }
+                            }
+                            else
+                            {
+                                for(z=offz; z<tz1; z++)
+                                {
+                                    commbuf[i0+z] += grid_th[i0t+z];
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+
+static void sum_fftgrid_dd(gmx_pme_t pme,real *fftgrid)
+{
+    ivec local_fft_ndata,local_fft_offset,local_fft_size;
+    pme_overlap_t *overlap;
+    int  send_nindex;
+    int  recv_index0,recv_nindex;
+#ifdef GMX_MPI
+    MPI_Status stat;
+#endif
+    int  ipulse,send_id,recv_id,datasize,gridsize,size_yx;
+    real *sendptr,*recvptr;
+    int  x,y,z,indg,indb;
+
+    /* Note that this routine is only used for forward communication.
+     * Since the force gathering, unlike the charge spreading,
+     * can be trivially parallelized over the particles,
+     * the backwards process is much simpler and can use the "old"
+     * communication setup.
+     */
+
+    gmx_parallel_3dfft_real_limits(pme->pfft_setupA,
+                                   local_fft_ndata,
+                                   local_fft_offset,
+                                   local_fft_size);
+
+    /* Currently supports only a single communication pulse */
+
+/* for(ipulse=0;ipulse<overlap->noverlap_nodes;ipulse++) */
+    if (pme->nnodes_minor > 1)
+    {
+        /* Major dimension */
+        overlap = &pme->overlap[1];
+
+        if (pme->nnodes_major > 1)
+        {
+             size_yx = pme->overlap[0].comm_data[0].send_nindex;
+        }
+        else
+        {
+            size_yx = 0;
+        }
+        datasize = (local_fft_ndata[XX]+size_yx)*local_fft_ndata[ZZ];
+
+        ipulse = 0;
+
+        send_id = overlap->send_id[ipulse];
+        recv_id = overlap->recv_id[ipulse];
+        send_nindex   = overlap->comm_data[ipulse].send_nindex;
+        /* recv_index0   = overlap->comm_data[ipulse].recv_index0; */
+        recv_index0 = 0;
+        recv_nindex   = overlap->comm_data[ipulse].recv_nindex;
+
+        sendptr = overlap->sendbuf;
+        recvptr = overlap->recvbuf;
+
+        /*
+        printf("node %d comm %2d x %2d x %2d\n",pme->nodeid,
+               local_fft_ndata[XX]+size_yx,send_nindex,local_fft_ndata[ZZ]);
+        printf("node %d send %f, %f\n",pme->nodeid,
+               sendptr[0],sendptr[send_nindex*datasize-1]);
+        */
+
+#ifdef GMX_MPI
+        MPI_Sendrecv(sendptr,send_nindex*datasize,GMX_MPI_REAL,
+                     send_id,ipulse,
+                     recvptr,recv_nindex*datasize,GMX_MPI_REAL,
+                     recv_id,ipulse,
+                     overlap->mpi_comm,&stat);
+#endif
+
+        for(x=0; x<local_fft_ndata[XX]; x++)
+        {
+            for(y=0; y<recv_nindex; y++)
+            {
+                indg = (x*local_fft_size[YY] + y)*local_fft_size[ZZ];
+                indb = (x*recv_nindex        + y)*local_fft_ndata[ZZ];
+                for(z=0; z<local_fft_ndata[ZZ]; z++)
+                {
+                    fftgrid[indg+z] += recvptr[indb+z];
+                }
+            }
+        }
+        if (pme->nnodes_major > 1)
+        {
+            sendptr = pme->overlap[0].sendbuf;
+            for(x=0; x<size_yx; x++)
+            {
+                for(y=0; y<recv_nindex; y++)
+                {
+                    indg = (x*local_fft_ndata[YY] + y)*local_fft_ndata[ZZ];
+                    indb = ((local_fft_ndata[XX] + x)*recv_nindex +y)*local_fft_ndata[ZZ];
+                    for(z=0; z<local_fft_ndata[ZZ]; z++)
+                    {
+                        sendptr[indg+z] += recvptr[indb+z];
+                    }
+                }
+            }
+        }
+    }
+
+    /* for(ipulse=0;ipulse<overlap->noverlap_nodes;ipulse++) */
+    if (pme->nnodes_major > 1)
+    {
+        /* Major dimension */
+        overlap = &pme->overlap[0];
+
+        datasize = local_fft_ndata[YY]*local_fft_ndata[ZZ];
+        gridsize = local_fft_size[YY] *local_fft_size[ZZ];
+
+        ipulse = 0;
+
+        send_id = overlap->send_id[ipulse];
+        recv_id = overlap->recv_id[ipulse];
+        send_nindex   = overlap->comm_data[ipulse].send_nindex;
+        /* recv_index0   = overlap->comm_data[ipulse].recv_index0; */
+        recv_index0 = 0;
+        recv_nindex   = overlap->comm_data[ipulse].recv_nindex;
+
+        sendptr = overlap->sendbuf;
+        recvptr = overlap->recvbuf;
+
+        if (debug != NULL)
+        {
+            fprintf(debug,"PME fftgrid comm %2d x %2d x %2d\n",
+                   send_nindex,local_fft_ndata[YY],local_fft_ndata[ZZ]);
+        }
+
+#ifdef GMX_MPI
+        MPI_Sendrecv(sendptr,send_nindex*datasize,GMX_MPI_REAL,
+                     send_id,ipulse,
+                     recvptr,recv_nindex*datasize,GMX_MPI_REAL,
+                     recv_id,ipulse,
+                     overlap->mpi_comm,&stat);
 #endif
-        
-        /* Note that the charge spreading and force gathering, which usually
-         * takes about the same amount of time as FFT+solve_pme,
-         * is always fully load balanced
-         * (unless the charge distribution is inhomogeneous).
-         */
-        
-        imbal = pme_load_imbalance(pme);
-        if (imbal >= 1.2 && pme->nodeid_major == 0 && pme->nodeid_minor == 0)
+
+        for(x=0; x<recv_nindex; x++)
         {
-            fprintf(stderr,
-                    "\n"
-                    "NOTE: The load imbalance in PME FFT and solve is %d%%.\n"
-                    "      For optimal PME load balancing\n"
-                    "      PME grid_x (%d) and grid_y (%d) should be divisible by #PME_nodes_x (%d)\n"
-                    "      and PME grid_y (%d) and grid_z (%d) should be divisible by #PME_nodes_y (%d)\n"
-                    "\n",
-                    (int)((imbal-1)*100 + 0.5),
-                    pme->nkx,pme->nky,pme->nnodes_major,
-                    pme->nky,pme->nkz,pme->nnodes_minor);
+            for(y=0; y<local_fft_ndata[YY]; y++)
+            {
+                indg = (x*local_fft_size[YY]  + y)*local_fft_size[ZZ];
+                indb = (x*local_fft_ndata[YY] + y)*local_fft_ndata[ZZ];
+                for(z=0; z<local_fft_ndata[ZZ]; z++)
+                {
+                    fftgrid[indg+z] += recvptr[indb+z];
+                }
+            }
         }
     }
+}
 
-    init_overlap_comm(&pme->overlap[0],pme->pme_order,
-#ifdef GMX_MPI
-                      pme->mpi_comm_d[0],
+
+static void spread_on_grid(gmx_pme_t pme,
+                           pme_atomcomm_t *atc,pmegrids_t *grids,
+                           gmx_bool bCalcSplines,gmx_bool bSpread,
+                           real *fftgrid)
+{
+    int nthread,thread;
+#ifdef PME_TIME_THREADS
+    gmx_cycles_t c1,c2,c3,ct1a,ct1b,ct1c;
+    static double cs1=0,cs2=0,cs3=0;
+    static double cs1a[6]={0,0,0,0,0,0};
+    static int cnt=0;
 #endif
-                      pme->nnodes_major,pme->nodeid_major,pme->nkx);
-    
-    init_overlap_comm(&pme->overlap[1],pme->pme_order,
-#ifdef GMX_MPI
-                      pme->mpi_comm_d[1],
+
+    nthread = pme->nthread;
+    assert(nthread>0);
+
+#ifdef PME_TIME_THREADS
+    c1 = omp_cyc_start();
 #endif
-                      pme->nnodes_minor,pme->nodeid_minor,pme->nky);
-    
-    snew(pme->bsp_mod[XX],pme->nkx);
-    snew(pme->bsp_mod[YY],pme->nky);
-    snew(pme->bsp_mod[ZZ],pme->nkz);
-    
-    /* Allocate data for the interpolation grid, including overlap */
-    pme->pmegrid_nx = pme->overlap[0].s2g1[pme->nodeid_major] -
-                      pme->overlap[0].s2g0[pme->nodeid_major];
-    pme->pmegrid_ny = pme->overlap[1].s2g1[pme->nodeid_minor] - 
-                      pme->overlap[1].s2g0[pme->nodeid_minor];
-    pme->pmegrid_nz = pme->nkz + pme->pme_order - 1;
-    
-    pme->pmegrid_start_ix = pme->overlap[0].s2g0[pme->nodeid_major];
-    pme->pmegrid_start_iy = pme->overlap[1].s2g0[pme->nodeid_minor];
-    pme->pmegrid_start_iz = 0;
-    
-    make_gridindex5_to_localindex(pme->nkx,
-                                  pme->pmegrid_start_ix,
-                                  pme->pmegrid_nx - (pme->pme_order-1),
-                                  &pme->nnx,&pme->fshx);
-    make_gridindex5_to_localindex(pme->nky,
-                                  pme->pmegrid_start_iy,
-                                  pme->pmegrid_ny - (pme->pme_order-1),
-                                  &pme->nny,&pme->fshy);
-    make_gridindex5_to_localindex(pme->nkz,
-                                  pme->pmegrid_start_iz,
-                                  pme->pmegrid_nz - (pme->pme_order-1),
-                                  &pme->nnz,&pme->fshz);
-    
-    snew(pme->pmegridA,pme->pmegrid_nx*pme->pmegrid_ny*pme->pmegrid_nz);
-    
-    /* For non-divisible grid we need pme_order iso pme_order-1 */
-    /* x overlap is copied in place: take padding into account.
-     * y is always copied through a buffer: we don't need padding in z,
-     * but we do need the overlap in x because of the communication order.
-     */
-    bufsizex = pme->pme_order*pme->pmegrid_ny*pme->pmegrid_nz;
-    bufsizey = pme->pme_order*pme->pmegrid_nx*pme->nkz;
-    bufsize  = (bufsizex>bufsizey) ? bufsizex : bufsizey;
-    
-    snew(pme->pmegrid_sendbuf,bufsize);
-    snew(pme->pmegrid_recvbuf,bufsize);
-    
-    ndata[0] = pme->nkx;
-    ndata[1] = pme->nky;
-    ndata[2] = pme->nkz;
-    
-    /* This routine will allocate the grid data to fit the FFTs */
-    gmx_parallel_3dfft_init(&pme->pfft_setupA,ndata,
-                            &pme->fftgridA,&pme->cfftgridA,
-                            pme->mpi_comm_d,
-                            pme->overlap[0].s2g0,pme->overlap[1].s2g0,
-                            bReproducible);
-    
-    if (bFreeEnergy)
-    {
-        snew(pme->pmegridB,pme->pmegrid_nx*pme->pmegrid_ny*pme->pmegrid_nz);    
-        gmx_parallel_3dfft_init(&pme->pfft_setupB,ndata,
-                                &pme->fftgridB,&pme->cfftgridB,
-                                pme->mpi_comm_d,
-                                pme->overlap[0].s2g0,pme->overlap[1].s2g0,
-                                bReproducible);
-    } else 
+    if (bCalcSplines)
     {
-        pme->pmegridB    = NULL;
-        pme->fftgridB    = NULL;
-        pme->cfftgridB   = NULL;
+#pragma omp parallel for num_threads(nthread) schedule(static)
+        for(thread=0; thread<nthread; thread++)
+        {
+            int start,end;
+
+            start = atc->n* thread   /nthread;
+            end   = atc->n*(thread+1)/nthread;
+
+            /* Compute fftgrid index for all atoms,
+             * with help of some extra variables.
+             */
+            calc_interpolation_idx(pme,atc,start,end,thread);
+        }
     }
-    
-    make_bspline_moduli(pme->bsp_mod,pme->nkx,pme->nky,pme->nkz,pme->pme_order);
-    
-    /* Use atc[0] for spreading */
-    init_atomcomm(pme,&pme->atc[0],cr,nnodes_major > 1 ? 0 : 1,TRUE);
-    if (pme->ndecompdim >= 2)
+#ifdef PME_TIME_THREADS
+    c1 = omp_cyc_end(c1);
+    cs1 += (double)c1;
+#endif
+
+#ifdef PME_TIME_THREADS
+    c2 = omp_cyc_start();
+#endif
+#pragma omp parallel for num_threads(nthread) schedule(static)
+    for(thread=0; thread<nthread; thread++)
     {
-        init_atomcomm(pme,&pme->atc[1],cr,1,FALSE);
+        splinedata_t *spline;
+        pmegrid_t *grid;
+
+        /* make local bsplines  */
+        if (grids == NULL || grids->nthread == 1)
+        {
+            spline = &atc->spline[0];
+
+            spline->n = atc->n;
+
+            grid = &grids->grid;
+        }
+        else
+        {
+            spline = &atc->spline[thread];
+
+            make_thread_local_ind(atc,thread,spline);
+
+            grid = &grids->grid_th[thread];
+        }
+
+        if (bCalcSplines)
+        {
+            make_bsplines(spline->theta,spline->dtheta,pme->pme_order,
+                          atc->fractx,spline->n,spline->ind,atc->q,pme->bFEP);
+        }
+
+        if (bSpread)
+        {
+            /* put local atoms on grid. */
+#ifdef PME_TIME_SPREAD
+            ct1a = omp_cyc_start();
+#endif
+            spread_q_bsplines_thread(grid,atc,spline,pme->spline_work);
+
+            if (grids->nthread > 1)
+            {
+                copy_local_grid(pme,grids,thread,fftgrid);
+            }
+#ifdef PME_TIME_SPREAD
+            ct1a = omp_cyc_end(ct1a);
+            cs1a[thread] += (double)ct1a;
+#endif
+        }
     }
-    
-    if (pme->nnodes == 1) {
-        pme->atc[0].n = homenr;
-        pme_realloc_atomcomm_things(&pme->atc[0]);
+#ifdef PME_TIME_THREADS
+    c2 = omp_cyc_end(c2);
+    cs2 += (double)c2;
+#endif
+
+    if (bSpread && grids->nthread > 1)
+    {
+#ifdef PME_TIME_THREADS
+        c3 = omp_cyc_start();
+#endif
+#pragma omp parallel for num_threads(grids->nthread) schedule(static)
+        for(thread=0; thread<grids->nthread; thread++)
+        {
+            reduce_threadgrid_overlap(pme,grids,thread,
+                                      fftgrid,
+                                      pme->overlap[0].sendbuf,
+                                      pme->overlap[1].sendbuf);
+#ifdef PRINT_PME_SENDBUF
+            print_sendbuf(pme,pme->overlap[0].sendbuf);
+#endif
+        }
+#ifdef PME_TIME_THREADS
+        c3 = omp_cyc_end(c3);
+        cs3 += (double)c3;
+#endif
+
+        if (pme->nnodes > 1)
+        {
+            /* Communicate the overlapping part of the fftgrid */
+            sum_fftgrid_dd(pme,fftgrid);
+        }
     }
-    
-    /* Use fft5d, order after FFT is y major, z, x minor */
-    pme->work_nalloc = pme->nkx;
-    snew(pme->work_mhx,pme->work_nalloc);
-    snew(pme->work_mhy,pme->work_nalloc);
-    snew(pme->work_mhz,pme->work_nalloc);
-    snew(pme->work_m2,pme->work_nalloc);
-    snew(pme->work_denom,pme->work_nalloc);
-    /* Allocate an aligned pointer for SSE operations, including 3 extra
-     * elements at the end since SSE operates on 4 elements at a time.
-     */
-    snew(pme->work_tmp1_alloc,pme->work_nalloc+8);
-    pme->work_tmp1 = (real *) (((size_t) pme->work_tmp1_alloc + 16) & (~((size_t) 15)));
-    snew(pme->work_m2inv,pme->work_nalloc);
 
-    *pmedata = pme;
-    
-    return 0;
+#ifdef PME_TIME_THREADS
+    cnt++;
+    if (cnt % 20 == 0)
+    {
+        printf("idx %.2f spread %.2f red %.2f",
+               cs1*1e-9,cs2*1e-9,cs3*1e-9);
+#ifdef PME_TIME_SPREAD
+        for(thread=0; thread<nthread; thread++)
+            printf(" %.2f",cs1a[thread]*1e-9);
+#endif
+        printf("\n");
+    }
+#endif
 }
 
-static void spread_on_grid(gmx_pme_t pme,
-                           pme_atomcomm_t *atc,real *grid,
-                           gmx_bool bCalcSplines,gmx_bool bSpread)
-{    
-    if (bCalcSplines)
-    {
-    
-        /* Compute fftgrid index for all atoms,
-         * with help of some extra variables.
-         */
-        calc_interpolation_idx(pme,atc);
-        
-        /* make local bsplines  */
-        make_bsplines(atc->theta,atc->dtheta,pme->pme_order,
-                      atc->fractx,atc->n,atc->q,pme->bFEP);
-    }    
-    
-    if (bSpread)
+
+static void dump_grid(FILE *fp,
+                      int sx,int sy,int sz,int nx,int ny,int nz,
+                      int my,int mz,const real *g)
+{
+    int x,y,z;
+
+    for(x=0; x<nx; x++)
     {
-        /* put local atoms on grid. */
-        spread_q_bsplines(pme,atc,grid);
+        for(y=0; y<ny; y++)
+        {
+            for(z=0; z<nz; z++)
+            {
+                fprintf(fp,"%2d %2d %2d %6.3f\n",
+                        sx+x,sy+y,sz+z,g[(x*my + y)*mz + z]);
+            }
+        }
     }
 }
 
+static void dump_local_fftgrid(gmx_pme_t pme,const real *fftgrid)
+{
+    ivec local_fft_ndata,local_fft_offset,local_fft_size;
+
+    gmx_parallel_3dfft_real_limits(pme->pfft_setupA,
+                                   local_fft_ndata,
+                                   local_fft_offset,
+                                   local_fft_size);
+
+    dump_grid(stderr,
+              pme->pmegrid_start_ix,
+              pme->pmegrid_start_iy,
+              pme->pmegrid_start_iz,
+              pme->pmegrid_nx-pme->pme_order+1,
+              pme->pmegrid_ny-pme->pme_order+1,
+              pme->pmegrid_nz-pme->pme_order+1,
+              local_fft_size[YY],
+              local_fft_size[ZZ],
+              fftgrid);
+}
+
+
 void gmx_pme_calc_energy(gmx_pme_t pme,int n,rvec *x,real *q,real *V)
 {
     pme_atomcomm_t *atc;
-    real *grid;
+    pmegrids_t *grid;
 
     if (pme->nnodes > 1)
     {
@@ -2350,6 +3918,11 @@ void gmx_pme_calc_energy(gmx_pme_t pme,int n,rvec *x,real *q,real *V)
     }
 
     atc = &pme->atc_energy;
+    atc->nthread   = 1;
+    if (atc->spline == NULL)
+    {
+        snew(atc->spline,atc->nthread);
+    }
     atc->nslab     = 1;
     atc->bSpread   = TRUE;
     atc->pme_order = pme->pme_order;
@@ -2357,13 +3930,13 @@ void gmx_pme_calc_energy(gmx_pme_t pme,int n,rvec *x,real *q,real *V)
     pme_realloc_atomcomm_things(atc);
     atc->x         = x;
     atc->q         = q;
-    
+
     /* We only use the A-charges grid */
-    grid = pme->pmegridA;
+    grid = &pme->pmegridA;
 
-    spread_on_grid(pme,atc,NULL,TRUE,FALSE);
+    spread_on_grid(pme,atc,NULL,TRUE,FALSE,pme->fftgridA);
 
-    *V = gather_energy_bsplines(pme,grid,atc);
+    *V = gather_energy_bsplines(pme,grid->grid.grid,atc);
 }
 
 
@@ -2399,12 +3972,12 @@ int gmx_pmeonly(gmx_pme_t pme,
     int  count;
     gmx_bool bEnerVir;
     gmx_large_int_t step,step_rel;
-    
-    
+
+
     pme_pp = gmx_pme_pp_init(cr);
-    
+
     init_nrnb(nrnb);
-    
+
     count = 0;
     do /****** this is a quasi-loop over time steps! */
     {
@@ -2415,32 +3988,32 @@ int gmx_pmeonly(gmx_pme_t pme,
                                   &pme->bFEP,&lambda,
                                   &bEnerVir,
                                   &step);
-        
+
         if (natoms == -1) {
             /* We should stop: break out of the loop */
             break;
         }
-        
+
         step_rel = step - ir->init_step;
-        
+
         if (count == 0)
             wallcycle_start(wcycle,ewcRUN);
-        
+
         wallcycle_start(wcycle,ewcPMEMESH);
-        
+
         dvdlambda = 0;
         clear_mat(vir);
         gmx_pme_do(pme,0,natoms,x_pp,f_pp,chargeA,chargeB,box,
                    cr,maxshift_x,maxshift_y,nrnb,wcycle,vir,ewaldcoeff,
                    &energy,lambda,&dvdlambda,
                    GMX_PME_DO_ALL_F | (bEnerVir ? GMX_PME_CALC_ENER_VIR : 0));
-        
+
         cycles = wallcycle_stop(wcycle,ewcPMEMESH);
-        
+
         gmx_pme_send_force_vir_ener(pme_pp,
                                     f_pp,vir,energy,dvdlambda,
                                     cycles);
-        
+
         count++;
 
         if (step_rel == wcycle_get_reset_counters(wcycle))
@@ -2449,10 +4022,10 @@ int gmx_pmeonly(gmx_pme_t pme,
             reset_pmeonly_counters(cr,wcycle,nrnb,ir,step_rel);
             wcycle_set_reset_counters(wcycle, 0);
         }
-        
+
     } /***** end of quasi-loop, we stop with the break above */
     while (TRUE);
-    
+
     return 0;
 }
 
@@ -2460,28 +4033,34 @@ int gmx_pme_do(gmx_pme_t pme,
                int start,       int homenr,
                rvec x[],        rvec f[],
                real *chargeA,   real *chargeB,
-               matrix box,     t_commrec *cr,
+               matrix box, t_commrec *cr,
                int  maxshift_x, int maxshift_y,
                t_nrnb *nrnb,    gmx_wallcycle_t wcycle,
                matrix vir,      real ewaldcoeff,
-               real *energy,    real lambda, 
+               real *energy,    real lambda,
                real *dvdlambda, int flags)
 {
     int     q,d,i,j,ntot,npme;
     int     nx,ny,nz;
     int     n_d,local_ny;
-    int     loop_count;
     pme_atomcomm_t *atc=NULL;
-    real *  grid=NULL;
+    pmegrids_t *pmegrid=NULL;
+    real    *grid=NULL;
     real    *ptr;
     rvec    *x_d,*f_d;
-    real    *charge=NULL,*q_d,vol;
+    real    *charge=NULL,*q_d;
     real    energy_AB[2];
     matrix  vir_AB[2];
-    gmx_bool    bClearF;
+    gmx_bool bClearF;
     gmx_parallel_3dfft_t pfft_setup;
     real *  fftgrid;
     t_complex * cfftgrid;
+    int     thread;
+    const gmx_bool bCalcEnerVir = flags & GMX_PME_CALC_ENER_VIR;
+    const gmx_bool bCalcF = flags & GMX_PME_CALC_F;
+
+    assert(pme->nnodes > 0);
+    assert(pme->nnodes == 1 || pme->ndecompdim > 0);
 
     if (pme->nnodes > 1) {
         atc = &pme->atc[0];
@@ -2497,21 +4076,22 @@ int gmx_pme_do(gmx_pme_t pme,
         /* This could be necessary for TPI */
         pme->atc[0].n = homenr;
     }
-    
+
     for(q=0; q<(pme->bFEP ? 2 : 1); q++) {
         if (q == 0) {
-            grid = pme->pmegridA;
+            pmegrid = &pme->pmegridA;
             fftgrid = pme->fftgridA;
             cfftgrid = pme->cfftgridA;
             pfft_setup = pme->pfft_setupA;
             charge = chargeA+start;
         } else {
-            grid = pme->pmegridB;
+            pmegrid = &pme->pmegridB;
             fftgrid = pme->fftgridB;
             cfftgrid = pme->cfftgridB;
             pfft_setup = pme->pfft_setupB;
             charge = chargeB+start;
         }
+        grid = pmegrid->grid.grid;
         /* Unpack structure */
         if (debug) {
             fprintf(debug,"PME: nnodes = %d, nodeid = %d\n",
@@ -2521,8 +4101,8 @@ int gmx_pme_do(gmx_pme_t pme,
                 gmx_fatal(FARGS,"No grid!");
         }
         where();
-        
-        m_inv_ur0(box,pme->recipbox); 
+
+        m_inv_ur0(box,pme->recipbox);
 
         if (pme->nnodes == 1) {
             atc = &pme->atc[0];
@@ -2556,9 +4136,9 @@ int gmx_pme_do(gmx_pme_t pme,
                     srenew(atc->pd,atc->pd_nalloc);
                 }
                 atc->maxshift = (atc->dimind==0 ? maxshift_x : maxshift_y);
-                pme_calc_pidx(n_d,pme->recipbox,x_d,atc);
+                pme_calc_pidx_wrapper(n_d,pme->recipbox,x_d,atc);
                 where();
-                
+
                 GMX_BARRIER(cr->mpi_comm_mygroup);
                 /* Redistribute x (only once) and qA or qB */
                 if (DOMAINDECOMP(cr)) {
@@ -2571,7 +4151,7 @@ int gmx_pme_do(gmx_pme_t pme,
 
             wallcycle_stop(wcycle,ewcPME_REDISTXF);
         }
-        
+
         if (debug)
             fprintf(debug,"Node= %6d, pme local particles=%6d\n",
                     cr->nodeid,atc->n);
@@ -2582,9 +4162,9 @@ int gmx_pme_do(gmx_pme_t pme,
 
             /* Spread the charges on a grid */
             GMX_MPE_LOG(ev_spread_on_grid_start);
-            
+
             /* Spread the charges on a grid */
-            spread_on_grid(pme,&pme->atc[0],grid,q==0,TRUE);
+            spread_on_grid(pme,&pme->atc[0],pmegrid,q==0,TRUE,fftgrid);
             GMX_MPE_LOG(ev_spread_on_grid_finish);
 
             if (q == 0)
@@ -2594,75 +4174,114 @@ int gmx_pme_do(gmx_pme_t pme,
             inc_nrnb(nrnb,eNR_SPREADQBSP,
                      pme->pme_order*pme->pme_order*pme->pme_order*atc->n);
 
-            wrap_periodic_pmegrid(pme,grid);
+            if (pme->nthread == 1)
+            {
+                wrap_periodic_pmegrid(pme,grid);
 
-            /* sum contributions to local grid from other nodes */
+                /* sum contributions to local grid from other nodes */
 #ifdef GMX_MPI
-            if (pme->nnodes > 1) {
-                GMX_BARRIER(cr->mpi_comm_mygroup);
-                gmx_sum_qgrid_dd(pme,grid,GMX_SUM_QGRID_FORWARD);
-                where();
-            }
+                if (pme->nnodes > 1)
+                {
+                    GMX_BARRIER(cr->mpi_comm_mygroup);
+                    gmx_sum_qgrid_dd(pme,grid,GMX_SUM_QGRID_FORWARD);
+                    where();
+                }
 #endif
-            where();
 
-            copy_pmegrid_to_fftgrid(pme,grid,fftgrid);
+                copy_pmegrid_to_fftgrid(pme,grid,fftgrid);
+            }
 
             wallcycle_stop(wcycle,ewcPME_SPREADGATHER);
-        }
-         
-        if (flags & GMX_PME_SOLVE)
-        {
-            /* do 3d-fft */ 
-            GMX_BARRIER(cr->mpi_comm_mygroup);
-            GMX_MPE_LOG(ev_gmxfft3d_start);
-            wallcycle_start(wcycle,ewcPME_FFT);
-            gmx_parallel_3dfft_execute(pfft_setup,GMX_FFT_REAL_TO_COMPLEX,fftgrid,cfftgrid);
-            wallcycle_stop(wcycle,ewcPME_FFT);
-            GMX_MPE_LOG(ev_gmxfft3d_finish);
-            where();
-            
-            /* solve in k-space for our local cells */
-            vol = det(box);
-            GMX_BARRIER(cr->mpi_comm_mygroup);
-            GMX_MPE_LOG(ev_solve_pme_start);
-            wallcycle_start(wcycle,ewcPME_SOLVE);
-            loop_count =
-                solve_pme_yzx(pme,cfftgrid,ewaldcoeff,vol,
-                              flags & GMX_PME_CALC_ENER_VIR,
-                              &energy_AB[q],vir_AB[q]);
-            wallcycle_stop(wcycle,ewcPME_SOLVE);
-            where();
-            GMX_MPE_LOG(ev_solve_pme_finish);
-            inc_nrnb(nrnb,eNR_SOLVEPME,loop_count);
+
+            /*
+            dump_local_fftgrid(pme,fftgrid);
+            exit(0);
+            */
         }
 
-        if ((flags & GMX_PME_CALC_F) ||
-            (flags & GMX_PME_CALC_POT))
+        /* Here we start a large thread parallel region */
+#pragma omp parallel for num_threads(pme->nthread) schedule(static)
+        for(thread=0; thread<pme->nthread; thread++)
         {
-            
-            /* do 3d-invfft */
-            GMX_BARRIER(cr->mpi_comm_mygroup);
-            GMX_MPE_LOG(ev_gmxfft3d_start);
-            where();
-            wallcycle_start(wcycle,ewcPME_FFT);
-            gmx_parallel_3dfft_execute(pfft_setup,GMX_FFT_COMPLEX_TO_REAL,cfftgrid,fftgrid);
-            wallcycle_stop(wcycle,ewcPME_FFT);
+            if (flags & GMX_PME_SOLVE)
+            {
+                int loop_count;
 
-            where();
-            GMX_MPE_LOG(ev_gmxfft3d_finish);
+                /* do 3d-fft */
+                if (thread == 0)
+                {
+                    GMX_BARRIER(cr->mpi_comm_mygroup);
+                    GMX_MPE_LOG(ev_gmxfft3d_start);
+                    wallcycle_start(wcycle,ewcPME_FFT);
+                }
+                gmx_parallel_3dfft_execute(pfft_setup,GMX_FFT_REAL_TO_COMPLEX,
+                                           fftgrid,cfftgrid,thread,wcycle);
+                if (thread == 0)
+                {
+                    wallcycle_stop(wcycle,ewcPME_FFT);
+                    GMX_MPE_LOG(ev_gmxfft3d_finish);
+                }
+                where();
 
-            if (pme->nodeid == 0)
-            {
-                ntot = pme->nkx*pme->nky*pme->nkz;
-                npme  = ntot*log((real)ntot)/log(2.0);
-                inc_nrnb(nrnb,eNR_FFT,2*npme);
+                /* solve in k-space for our local cells */
+                if (thread == 0)
+                {
+                    GMX_BARRIER(cr->mpi_comm_mygroup);
+                    GMX_MPE_LOG(ev_solve_pme_start);
+                    wallcycle_start(wcycle,ewcPME_SOLVE);
+                }
+                loop_count =
+                    solve_pme_yzx(pme,cfftgrid,ewaldcoeff,
+                                  box[XX][XX]*box[YY][YY]*box[ZZ][ZZ],
+                                  bCalcEnerVir,
+                                  pme->nthread,thread);
+                if (thread == 0)
+                {
+                    wallcycle_stop(wcycle,ewcPME_SOLVE);
+                    where();
+                    GMX_MPE_LOG(ev_solve_pme_finish);
+                    inc_nrnb(nrnb,eNR_SOLVEPME,loop_count);
+                }
             }
 
-            wallcycle_start(wcycle,ewcPME_SPREADGATHER);
+            if (bCalcF)
+            {
+                /* do 3d-invfft */
+                if (thread == 0)
+                {
+                    GMX_BARRIER(cr->mpi_comm_mygroup);
+                    GMX_MPE_LOG(ev_gmxfft3d_start);
+                    where();
+                    wallcycle_start(wcycle,ewcPME_FFT);
+                }
+                gmx_parallel_3dfft_execute(pfft_setup,GMX_FFT_COMPLEX_TO_REAL,
+                                           cfftgrid,fftgrid,thread,wcycle);
+                if (thread == 0)
+                {
+                    wallcycle_stop(wcycle,ewcPME_FFT);
 
-            copy_fftgrid_to_pmegrid(pme,fftgrid,grid);
+                    where();
+                    GMX_MPE_LOG(ev_gmxfft3d_finish);
+
+                    if (pme->nodeid == 0)
+                    {
+                        ntot = pme->nkx*pme->nky*pme->nkz;
+                        npme  = ntot*log((real)ntot)/log(2.0);
+                        inc_nrnb(nrnb,eNR_FFT,2*npme);
+                    }
+
+                    wallcycle_start(wcycle,ewcPME_SPREADGATHER);
+                }
+
+                copy_fftgrid_to_pmegrid(pme,fftgrid,grid,pme->nthread,thread);
+            }
+        }
+        /* End of thread parallel section.
+         * With MPI we have to synchronize here before gmx_sum_qgrid_dd.
+         */
 
+        if (bCalcF)
+        {
             /* distribute local grid to all nodes */
 #ifdef GMX_MPI
             if (pme->nnodes > 1) {
@@ -2673,34 +4292,45 @@ int gmx_pme_do(gmx_pme_t pme,
             where();
 
             unwrap_periodic_pmegrid(pme,grid);
-        }
 
-        if (flags & GMX_PME_CALC_F)
-        {
             /* interpolate forces for our local atoms */
             GMX_BARRIER(cr->mpi_comm_mygroup);
             GMX_MPE_LOG(ev_gather_f_bsplines_start);
 
             where();
-            
+
             /* If we are running without parallelization,
              * atc->f is the actual force array, not a buffer,
              * therefore we should not clear it.
              */
             bClearF = (q == 0 && PAR(cr));
-            gather_f_bsplines(pme,grid,bClearF,&pme->atc[0],
-                              pme->bFEP ? (q==0 ? 1.0-lambda : lambda) : 1.0);
+#pragma omp parallel for num_threads(pme->nthread) schedule(static)
+            for(thread=0; thread<pme->nthread; thread++)
+            {
+                gather_f_bsplines(pme,grid,bClearF,atc,
+                                  &atc->spline[thread],
+                                  pme->bFEP ? (q==0 ? 1.0-lambda : lambda) : 1.0);
+            }
+
             where();
-            
+
             GMX_MPE_LOG(ev_gather_f_bsplines_finish);
-            
+
             inc_nrnb(nrnb,eNR_GATHERFBSP,
                      pme->pme_order*pme->pme_order*pme->pme_order*pme->atc[0].n);
             wallcycle_stop(wcycle,ewcPME_SPREADGATHER);
-       }
+        }
+
+        if (bCalcEnerVir)
+        {
+            /* This should only be called on the master thread
+             * and after the threads have synchronized.
+             */
+            get_pme_ener_vir(pme,pme->nthread,&energy_AB[q],vir_AB[q]);
+        }
     } /* of q-loop */
-    
-    if ((flags & GMX_PME_CALC_F) && pme->nnodes > 1) {
+
+    if (bCalcF && pme->nnodes > 1) {
         wallcycle_start(wcycle,ewcPME_REDISTXF);
         for(d=0; d<pme->ndecompdim; d++)
         {
@@ -2727,20 +4357,34 @@ int gmx_pme_do(gmx_pme_t pme,
         wallcycle_stop(wcycle,ewcPME_REDISTXF);
     }
     where();
-    
-    if (!pme->bFEP) {
-        *energy = energy_AB[0];
-        m_add(vir,vir_AB[0],vir);
-    } else {
-        *energy = (1.0-lambda)*energy_AB[0] + lambda*energy_AB[1];
-        *dvdlambda += energy_AB[1] - energy_AB[0];
-        for(i=0; i<DIM; i++)
-            for(j=0; j<DIM; j++)
-                vir[i][j] += (1.0-lambda)*vir_AB[0][i][j] + lambda*vir_AB[1][i][j];
+
+    if (bCalcEnerVir)
+    {
+        if (!pme->bFEP) {
+            *energy = energy_AB[0];
+            m_add(vir,vir_AB[0],vir);
+        } else {
+            *energy = (1.0-lambda)*energy_AB[0] + lambda*energy_AB[1];
+            *dvdlambda += energy_AB[1] - energy_AB[0];
+            for(i=0; i<DIM; i++)
+            {
+                for(j=0; j<DIM; j++)
+                {
+                    vir[i][j] += (1.0-lambda)*vir_AB[0][i][j] + 
+                        lambda*vir_AB[1][i][j];
+                }
+            }
+        }
+    }
+    else
+    {
+        *energy = 0;
     }
 
     if (debug)
+    {
         fprintf(debug,"PME mesh energy: %g\n",*energy);
-    
+    }
+
     return 0;
 }