From 9ad561b1b471ed841558b15aa8465596b0a29354 Mon Sep 17 00:00:00 2001
From: Berk Hess <hess@kth.se>
Date: Tue, 3 Sep 2019 11:06:54 +0200
Subject: [PATCH] Extract DDSystemInfo from gmx_domdec_comm_t

This is only refactoring.
This is preparation for separating the DD grid choice from
the initialization of gmx_domdec_t.

Change-Id: I83d8ecdd1a4d21d0a791c463d092f66d0b28df51
---
 src/gromacs/domdec/cellsizes.cpp     |  12 +--
 src/gromacs/domdec/domdec.cpp        | 134 ++++++++++++++-------------
 src/gromacs/domdec/domdec.h          |   4 +-
 src/gromacs/domdec/domdec_internal.h |  25 +++--
 src/gromacs/domdec/domdec_setup.cpp  |  17 ++--
 src/gromacs/domdec/partition.cpp     |  16 ++--
 6 files changed, 113 insertions(+), 95 deletions(-)

diff --git a/src/gromacs/domdec/cellsizes.cpp b/src/gromacs/domdec/cellsizes.cpp
index 8dbe017254..22c9e6f4bd 100644
--- a/src/gromacs/domdec/cellsizes.cpp
+++ b/src/gromacs/domdec/cellsizes.cpp
@@ -93,7 +93,7 @@ static void set_pme_maxshift(gmx_domdec_t *dd, gmx_ddpme_t *ddpme,
          * between performance and support for most charge-group/cut-off
          * combinations.
          */
-        range  = 2.0/3.0*comm->cutoff/ddbox->box_size[ddpme->dim];
+        range  = 2.0/3.0*comm->systemInfo.cutoff/ddbox->box_size[ddpme->dim];
         /* Avoid extra communication when we are exactly at a boundary */
         range *= 0.999;
 
@@ -192,7 +192,7 @@ static real cellsize_min_dlb(gmx_domdec_comm_t *comm, int dim_ind, int dim)
         /* The cut-off might have changed, e.g. by PME load balacning,
          * from the value used to set comm->cellsize_min, so check it.
          */
-        cellsize_min = std::max(cellsize_min, comm->cutoff/comm->cd[dim_ind].np_dlb);
+        cellsize_min = std::max(cellsize_min, comm->systemInfo.cutoff/comm->cd[dim_ind].np_dlb);
 
         if (comm->bPMELoadBalDLBLimits)
         {
@@ -246,7 +246,7 @@ set_dd_cell_sizes_slb(gmx_domdec_t *dd, const gmx_ddbox_t *ddbox,
                     break;
             }
             real cellsize = cell_dx*ddbox->skew_fac[d];
-            while (cellsize*npulse[d] < comm->cutoff)
+            while (cellsize*npulse[d] < comm->systemInfo.cutoff)
             {
                 npulse[d]++;
             }
@@ -276,7 +276,7 @@ set_dd_cell_sizes_slb(gmx_domdec_t *dd, const gmx_ddbox_t *ddbox,
                 real cell_dx  = ddbox->box_size[d]*comm->slb_frac[d][j];
                 cell_x[j+1]   = cell_x[j] + cell_dx;
                 real cellsize = cell_dx*ddbox->skew_fac[d];
-                while (cellsize*npulse[d] < comm->cutoff &&
+                while (cellsize*npulse[d] < comm->systemInfo.cutoff &&
                        npulse[d] < dd->nc[d]-1)
                 {
                     npulse[d]++;
@@ -301,7 +301,7 @@ set_dd_cell_sizes_slb(gmx_domdec_t *dd, const gmx_ddbox_t *ddbox,
             sprintf(error_string,
                     "The box size in direction %c (%f) times the triclinic skew factor (%f) is too small for a cut-off of %f with %d domain decomposition cells, use 1 or more than %d %s or increase the box size in this direction",
                     dim2char(d), ddbox->box_size[d], ddbox->skew_fac[d],
-                    comm->cutoff,
+                    comm->systemInfo.cutoff,
                     dd->nc[d], dd->nc[d],
                     dd->nnodes > dd->nc[d] ? "cells" : "ranks");
 
@@ -621,7 +621,7 @@ static void set_dd_cell_sizes_dlb_root(gmx_domdec_t *dd,
 
     real cellsize_limit_f  = cellsize_min_dlb(comm, d, dim)/ddbox->box_size[dim];
     cellsize_limit_f      *= DD_CELL_MARGIN;
-    real dist_min_f_hard   = grid_jump_limit(comm, comm->cutoff, d)/ddbox->box_size[dim];
+    real dist_min_f_hard   = grid_jump_limit(comm, comm->systemInfo.cutoff, d)/ddbox->box_size[dim];
     real dist_min_f        = dist_min_f_hard * DD_CELL_MARGIN;
     if (ddbox->tric_dir[dim])
     {
diff --git a/src/gromacs/domdec/domdec.cpp b/src/gromacs/domdec/domdec.cpp
index 21a5bb173e..ec25d892e5 100644
--- a/src/gromacs/domdec/domdec.cpp
+++ b/src/gromacs/domdec/domdec.cpp
@@ -649,34 +649,31 @@ void dd_atom_sum_real(gmx_domdec_t *dd, real v[])
 
 real dd_cutoff_multibody(const gmx_domdec_t *dd)
 {
-    gmx_domdec_comm_t *comm;
-    int                di;
-    real               r;
-
-    comm = dd->comm;
+    const gmx_domdec_comm_t &comm       = *dd->comm;
+    const DDSystemInfo      &systemInfo = comm.systemInfo;
 
-    r = -1;
-    if (comm->haveInterDomainMultiBodyBondeds)
+    real                     r = -1;
+    if (systemInfo.haveInterDomainMultiBodyBondeds)
     {
-        if (comm->cutoff_mbody > 0)
+        if (comm.cutoff_mbody > 0)
         {
-            r = comm->cutoff_mbody;
+            r = comm.cutoff_mbody;
         }
         else
         {
             /* cutoff_mbody=0 means we do not have DLB */
-            r = comm->cellsize_min[dd->dim[0]];
-            for (di = 1; di < dd->ndim; di++)
+            r = comm.cellsize_min[dd->dim[0]];
+            for (int di = 1; di < dd->ndim; di++)
             {
-                r = std::min(r, comm->cellsize_min[dd->dim[di]]);
+                r = std::min(r, comm.cellsize_min[dd->dim[di]]);
             }
-            if (comm->bBondComm)
+            if (comm.bBondComm)
             {
-                r = std::max(r, comm->cutoff_mbody);
+                r = std::max(r, comm.cutoff_mbody);
             }
             else
             {
-                r = std::min(r, comm->cutoff);
+                r = std::min(r, systemInfo.cutoff);
             }
         }
     }
@@ -690,7 +687,7 @@ real dd_cutoff_twobody(const gmx_domdec_t *dd)
 
     r_mb = dd_cutoff_multibody(dd);
 
-    return std::max(dd->comm->cutoff, r_mb);
+    return std::max(dd->comm->systemInfo.cutoff, r_mb);
 }
 
 
@@ -2157,10 +2154,12 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
         setupUpdateGroups(mdlog, *mtop, *ir, cutoffMargin, cr->nnodes, comm);
     }
 
+    DDSystemInfo &systemInfo = comm->systemInfo;
+
     // TODO: Check whether all bondeds are within update groups
-    comm->haveInterDomainBondeds          = (mtop->natoms > gmx_mtop_num_molecules(*mtop) ||
-                                             mtop->bIntermolecularInteractions);
-    comm->haveInterDomainMultiBodyBondeds = (multi_body_bondeds_count(mtop) > 0);
+    systemInfo.haveInterDomainBondeds          = (mtop->natoms > gmx_mtop_num_molecules(*mtop) ||
+                                                  mtop->bIntermolecularInteractions);
+    systemInfo.haveInterDomainMultiBodyBondeds = (multi_body_bondeds_count(mtop) > 0);
 
     if (comm->useUpdateGroups)
     {
@@ -2179,17 +2178,17 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
          * so we don't need if statements everywhere in the code.
          * We use sqrt, since the cut-off is squared in some places.
          */
-        comm->cutoff   = GMX_CUTOFF_INF;
+        systemInfo.cutoff = GMX_CUTOFF_INF;
     }
     else
     {
-        comm->cutoff   = atomToAtomIntoDomainToDomainCutoff(*comm, ir->rlist);
+        systemInfo.cutoff = atomToAtomIntoDomainToDomainCutoff(*comm, ir->rlist);
     }
-    comm->cutoff_mbody = 0;
+    systemInfo.minCutoffForMultiBody = 0;
 
     /* Determine the minimum cell size limit, affected by many factors */
-    comm->cellsize_limit = 0;
-    comm->bBondComm      = FALSE;
+    systemInfo.cellsizeLimit = 0;
+    comm->bBondComm          = FALSE;
 
     /* We do not allow home atoms to move beyond the neighboring domain
      * between domain decomposition steps, which limits the cell size.
@@ -2207,8 +2206,8 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
             "Minimum cell size due to atom displacement: %.3f nm",
             limitForAtomDisplacement);
 
-    comm->cellsize_limit = std::max(comm->cellsize_limit,
-                                    limitForAtomDisplacement);
+    systemInfo.cellsizeLimit = std::max(systemInfo.cellsizeLimit,
+                                        limitForAtomDisplacement);
 
     /* TODO: PME decomposition currently requires atoms not to be more than
      *       2/3 of comm->cutoff, which is >=rlist, outside of their domain.
@@ -2219,27 +2218,29 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
      *       Note that we would need to improve the pairlist buffer case.
      */
 
-    if (comm->haveInterDomainBondeds)
+    if (systemInfo.haveInterDomainBondeds)
     {
         if (options.minimumCommunicationRange > 0)
         {
-            comm->cutoff_mbody = atomToAtomIntoDomainToDomainCutoff(*comm, options.minimumCommunicationRange);
+            systemInfo.minCutoffForMultiBody =
+                atomToAtomIntoDomainToDomainCutoff(*comm, options.minimumCommunicationRange);
             if (options.useBondedCommunication)
             {
-                comm->bBondComm = (comm->cutoff_mbody > comm->cutoff);
+                comm->bBondComm = (systemInfo.minCutoffForMultiBody > systemInfo.cutoff);
             }
             else
             {
-                comm->cutoff = std::max(comm->cutoff, comm->cutoff_mbody);
+                systemInfo.cutoff = std::max(systemInfo.cutoff,
+                                             systemInfo.minCutoffForMultiBody);
             }
-            r_bonded_limit = comm->cutoff_mbody;
+            r_bonded_limit = systemInfo.minCutoffForMultiBody;
         }
         else if (ir->bPeriodicMols)
         {
             /* Can not easily determine the required cut-off */
             GMX_LOG(mdlog.warning).appendText("NOTE: Periodic molecules are present in this system. Because of this, the domain decomposition algorithm cannot easily determine the minimum cell size that it requires for treating bonded interactions. Instead, domain decomposition will assume that half the non-bonded cut-off will be a suitable lower bound.");
-            comm->cutoff_mbody = comm->cutoff/2;
-            r_bonded_limit     = comm->cutoff_mbody;
+            systemInfo.minCutoffForMultiBody = systemInfo.cutoff/2;
+            r_bonded_limit                   = systemInfo.minCutoffForMultiBody;
         }
         else
         {
@@ -2259,7 +2260,7 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
              */
             if (options.useBondedCommunication)
             {
-                if (std::max(r_2b, r_mb) > comm->cutoff)
+                if (std::max(r_2b, r_mb) > comm->systemInfo.cutoff)
                 {
                     r_bonded        = std::max(r_2b, r_mb);
                     r_bonded_limit  = tenPercentMargin*r_bonded;
@@ -2268,7 +2269,7 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
                 else
                 {
                     r_bonded       = r_mb;
-                    r_bonded_limit = std::min(tenPercentMargin*r_bonded, comm->cutoff);
+                    r_bonded_limit = std::min(tenPercentMargin*r_bonded, systemInfo.cutoff);
                 }
                 /* We determine cutoff_mbody later */
             }
@@ -2277,16 +2278,17 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
                 /* No special bonded communication,
                  * simply increase the DD cut-off.
                  */
-                r_bonded_limit     = tenPercentMargin*std::max(r_2b, r_mb);
-                comm->cutoff_mbody = r_bonded_limit;
-                comm->cutoff       = std::max(comm->cutoff, comm->cutoff_mbody);
+                r_bonded_limit                   = tenPercentMargin*std::max(r_2b, r_mb);
+                systemInfo.minCutoffForMultiBody = r_bonded_limit;
+                systemInfo.cutoff                = std::max(systemInfo.cutoff,
+                                                            systemInfo.minCutoffForMultiBody);
             }
         }
         GMX_LOG(mdlog.info).appendTextFormatted(
                 "Minimum cell size due to bonded interactions: %.3f nm",
                 r_bonded_limit);
 
-        comm->cellsize_limit = std::max(comm->cellsize_limit, r_bonded_limit);
+        systemInfo.cellsizeLimit = std::max(systemInfo.cellsizeLimit, r_bonded_limit);
     }
 
     real rconstr = 0;
@@ -2297,7 +2299,7 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
         GMX_LOG(mdlog.info).appendTextFormatted(
                 "Estimated maximum distance required for P-LINCS: %.3f nm",
                 rconstr);
-        if (rconstr > comm->cellsize_limit)
+        if (rconstr > systemInfo.cellsizeLimit)
         {
             GMX_LOG(mdlog.info).appendText("This distance will limit the DD cell size, you can override this with -rcon");
         }
@@ -2313,7 +2315,7 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
                 options.constraintCommunicationRange);
         rconstr = options.constraintCommunicationRange;
     }
-    comm->cellsize_limit = std::max(comm->cellsize_limit, rconstr);
+    systemInfo.cellsizeLimit = std::max(systemInfo.cellsizeLimit, rconstr);
 
     comm->cgs_gl = gmx_mtop_global_cgs(mtop);
 
@@ -2346,8 +2348,7 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
                            options.numPmeRanks,
                            !isDlbDisabled(comm),
                            options.dlbScaling,
-                           comm->cellsize_limit, comm->cutoff,
-                           comm->haveInterDomainBondeds);
+                           systemInfo);
 
         if (ddSetup.numDomains[XX] == 0)
         {
@@ -2369,7 +2370,7 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
     }
 
     const real acs = average_cellsize_min(*ddbox, ddSetup.numDomains);
-    if (acs < comm->cellsize_limit)
+    if (acs < systemInfo.cellsizeLimit)
     {
         if (options.numCells[XX] <= 0)
         {
@@ -2379,7 +2380,7 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
         {
             gmx_fatal_collective(FARGS, cr->mpi_comm_mysim, MASTER(cr),
                                  "The initial cell size (%f) is smaller than the cell size limit (%f), change options -dd, -rdd or -rcon, see the log file for details",
-                                 acs, comm->cellsize_limit);
+                                 acs, systemInfo.cellsizeLimit);
         }
     }
 
@@ -2467,7 +2468,10 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
         comm->slb_frac[ZZ] = get_slb_frac(mdlog, "z", dd->nc[ZZ], options.cellSizeZ);
     }
 
-    if (comm->haveInterDomainBondeds && comm->cutoff_mbody == 0)
+    /* Set the multi-body cut-off and cellsize limit for DLB */
+    comm->cutoff_mbody   = systemInfo.minCutoffForMultiBody;
+    comm->cellsize_limit = systemInfo.cellsizeLimit;
+    if (systemInfo.haveInterDomainBondeds && comm->cutoff_mbody == 0)
     {
         if (comm->bBondComm || !isDlbDisabled(comm))
         {
@@ -2486,15 +2490,15 @@ static void set_dd_limits_and_grid(const gmx::MDLogger &mdlog,
             if (!comm->bBondComm)
             {
                 /* Without bBondComm do not go beyond the n.b. cut-off */
-                comm->cutoff_mbody = std::min(comm->cutoff_mbody, comm->cutoff);
-                if (comm->cellsize_limit >= comm->cutoff)
+                comm->cutoff_mbody = std::min(comm->cutoff_mbody, systemInfo.cutoff);
+                if (comm->cellsize_limit >= systemInfo.cutoff)
                 {
                     /* We don't loose a lot of efficieny
                      * when increasing it to the n.b. cut-off.
                      * It can even be slightly faster, because we need
                      * less checks for the communication setup.
                      */
-                    comm->cutoff_mbody = comm->cutoff;
+                    comm->cutoff_mbody = systemInfo.cutoff;
                 }
             }
             /* Check if we did not end up below our original limit */
@@ -2636,7 +2640,7 @@ static void writeSettings(gmx::TextWriter       *log,
     const bool haveInterDomainVsites =
         (countInterUpdategroupVsites(*mtop, comm->updateGroupingPerMoleculetype) != 0);
 
-    if (comm->haveInterDomainBondeds ||
+    if (comm->systemInfo.haveInterDomainBondeds ||
         haveInterDomainVsites ||
         dd->splitConstraints || dd->splitSettles)
     {
@@ -2651,7 +2655,7 @@ static void writeSettings(gmx::TextWriter       *log,
         }
 
         log->writeLineFormatted("The maximum allowed distance for %s involved in interactions is:", decompUnits.c_str());
-        log->writeLineFormatted("%40s  %-7s %6.3f nm", "non-bonded interactions", "", comm->cutoff);
+        log->writeLineFormatted("%40s  %-7s %6.3f nm", "non-bonded interactions", "", comm->systemInfo.cutoff);
 
         if (bDynLoadBal)
         {
@@ -2670,14 +2674,14 @@ static void writeSettings(gmx::TextWriter       *log,
             }
         }
 
-        if (comm->haveInterDomainBondeds)
+        if (comm->systemInfo.haveInterDomainBondeds)
         {
             log->writeLineFormatted("%40s  %-7s %6.3f nm",
                                     "two-body bonded interactions", "(-rdd)",
-                                    std::max(comm->cutoff, comm->cutoff_mbody));
+                                    std::max(comm->systemInfo.cutoff, comm->cutoff_mbody));
             log->writeLineFormatted("%40s  %-7s %6.3f nm",
                                     "multi-body bonded interactions", "(-rdd)",
-                                    (comm->bBondComm || isDlbOn(dd->comm)) ? comm->cutoff_mbody : std::min(comm->cutoff, limit));
+                                    (comm->bBondComm || isDlbOn(dd->comm)) ? comm->cutoff_mbody : std::min(comm->systemInfo.cutoff, limit));
         }
         if (haveInterDomainVsites)
         {
@@ -2735,7 +2739,7 @@ static void set_cell_limits_dlb(const gmx::MDLogger &mdlog,
     comm->cellsize_limit = std::max(comm->cellsize_limit, comm->cutoff_mbody);
 
     /* Determine the maximum required number of grid pulses */
-    if (comm->cellsize_limit >= comm->cutoff)
+    if (comm->cellsize_limit >= comm->systemInfo.cutoff)
     {
         /* Only a single pulse is required */
         npulse = 1;
@@ -2748,7 +2752,7 @@ static void set_cell_limits_dlb(const gmx::MDLogger &mdlog,
          * Later cellsize_limit is redetermined,
          * so we can not miss interactions due to this rounding.
          */
-        npulse = static_cast<int>(0.96 + comm->cutoff/comm->cellsize_limit);
+        npulse = static_cast<int>(0.96 + comm->systemInfo.cutoff/comm->cellsize_limit);
     }
     else
     {
@@ -2763,7 +2767,7 @@ static void set_cell_limits_dlb(const gmx::MDLogger &mdlog,
         for (d = 0; d < dd->ndim; d++)
         {
             dim      = dd->dim[d];
-            npulse_d = static_cast<int>(1 + dd->nc[dim]*comm->cutoff
+            npulse_d = static_cast<int>(1 + dd->nc[dim]*comm->systemInfo.cutoff
                                         /(ddbox->box_size[dim]*ddbox->skew_fac[dim]*dlb_scale));
             npulse_d_max = std::max(npulse_d_max, npulse_d);
         }
@@ -2793,26 +2797,26 @@ static void set_cell_limits_dlb(const gmx::MDLogger &mdlog,
     if (!comm->bVacDLBNoLimit)
     {
         comm->cellsize_limit = std::max(comm->cellsize_limit,
-                                        comm->cutoff/comm->maxpulse);
+                                        comm->systemInfo.cutoff/comm->maxpulse);
     }
     comm->cellsize_limit = std::max(comm->cellsize_limit, comm->cutoff_mbody);
     /* Set the minimum cell size for each DD dimension */
     for (d = 0; d < dd->ndim; d++)
     {
         if (comm->bVacDLBNoLimit ||
-            comm->cd[d].np_dlb*comm->cellsize_limit >= comm->cutoff)
+            comm->cd[d].np_dlb*comm->cellsize_limit >= comm->systemInfo.cutoff)
         {
             comm->cellsize_min_dlb[dd->dim[d]] = comm->cellsize_limit;
         }
         else
         {
             comm->cellsize_min_dlb[dd->dim[d]] =
-                comm->cutoff/comm->cd[d].np_dlb;
+                comm->systemInfo.cutoff/comm->cd[d].np_dlb;
         }
     }
     if (comm->cutoff_mbody <= 0)
     {
-        comm->cutoff_mbody = std::min(comm->cutoff, comm->cellsize_limit);
+        comm->cutoff_mbody = std::min(comm->systemInfo.cutoff, comm->cellsize_limit);
     }
     if (isDlbOn(comm))
     {
@@ -2826,7 +2830,7 @@ gmx_bool dd_bonded_molpbc(const gmx_domdec_t *dd, int ePBC)
      * or we use domain decomposition for each periodic dimension,
      * we do not need to take pbc into account for the bonded interactions.
      */
-    return (ePBC != epbcNONE && dd->comm->haveInterDomainBondeds &&
+    return (ePBC != epbcNONE && dd->comm->systemInfo.haveInterDomainBondeds &&
             !(dd->nc[XX] > 1 &&
               dd->nc[YY] > 1 &&
               (dd->nc[ZZ] > 1 || ePBC == epbcXY)));
@@ -2864,7 +2868,7 @@ static void set_ddgrid_parameters(const gmx::MDLogger &mdlog,
 
     if (debug)
     {
-        fprintf(debug, "The DD cut-off is %f\n", comm->cutoff);
+        fprintf(debug, "The DD cut-off is %f\n", comm->systemInfo.cutoff);
     }
     if (!isDlbDisabled(comm))
     {
@@ -2880,7 +2884,7 @@ static void set_ddgrid_parameters(const gmx::MDLogger &mdlog,
     else
     {
         vol_frac =
-            (1 + comm_box_frac(dd->nc, comm->cutoff, ddbox))/static_cast<double>(dd->nnodes);
+            (1 + comm_box_frac(dd->nc, comm->systemInfo.cutoff, ddbox))/static_cast<double>(dd->nnodes);
     }
     if (debug)
     {
@@ -3060,7 +3064,7 @@ gmx_bool change_dd_cutoff(t_commrec     *cr,
 
     if (bCutoffAllowed)
     {
-        cr->dd->comm->cutoff = cutoffRequested;
+        cr->dd->comm->systemInfo.cutoff = cutoffRequested;
     }
 
     return bCutoffAllowed;
diff --git a/src/gromacs/domdec/domdec.h b/src/gromacs/domdec/domdec.h
index d140cca732..6f8fa8c8ef 100644
--- a/src/gromacs/domdec/domdec.h
+++ b/src/gromacs/domdec/domdec.h
@@ -67,6 +67,7 @@
 #include "gromacs/utility/real.h"
 
 struct cginfo_mb_t;
+struct DDSystemInfo;
 struct gmx_domdec_t;
 struct gmx_ddbox_t;
 struct gmx_domdec_zones_t;
@@ -338,7 +339,6 @@ dd_choose_grid(const gmx::MDLogger &mdlog,
                const matrix box, const gmx_ddbox_t *ddbox,
                int numPmeRanksRequested,
                gmx_bool bDynLoadBal, real dlb_scale,
-               real cellsize_limit, real cutoff_dd,
-               gmx_bool bInterCGBondeds);
+               const DDSystemInfo &systemInfo);
 
 #endif
diff --git a/src/gromacs/domdec/domdec_internal.h b/src/gromacs/domdec/domdec_internal.h
index bd7b57f9aa..0572224147 100644
--- a/src/gromacs/domdec/domdec_internal.h
+++ b/src/gromacs/domdec/domdec_internal.h
@@ -435,6 +435,22 @@ struct dd_comm_setup_work_t
     int                    nsend_zone = 0;
 };
 
+/*! \brief Information about the simulated system */
+struct DDSystemInfo
+{
+    //! Are there inter-domain bonded interactions?
+    bool haveInterDomainBondeds          = false;
+    //! Are there inter-domain multi-body interactions?
+    bool haveInterDomainMultiBodyBondeds = false;
+
+    //! Cut-off for multi-body interactions
+    real minCutoffForMultiBody = 0;
+    //! Cut-off for non-bonded/2-body interactions
+    real cutoff = 0;
+    //! The lower limit for the DD cell size
+    real cellsizeLimit = 0;
+};
+
 /*! \brief Struct for domain decomposition communication
  *
  * This struct contains most information about domain decomposition
@@ -490,10 +506,6 @@ struct gmx_domdec_comm_t // NOLINT (clang-analyzer-optin.performance.Padding)
     //! Centers of mass of local update groups
     std::unique_ptr<gmx::UpdateGroupsCog> updateGroupsCog;
 
-    /* Are there charge groups? */
-    bool haveInterDomainBondeds          = false; /**< Are there inter-domain bonded interactions? */
-    bool haveInterDomainMultiBodyBondeds = false; /**< Are there inter-domain multi-body interactions? */
-
     /* Data for the optional bonded interaction atom communication range */
     /**< Only communicate atoms beyond the non-bonded cut-off when they are involved in bonded interactions with non-local atoms */
     gmx_bool  bBondComm = false;
@@ -512,11 +524,12 @@ struct gmx_domdec_comm_t // NOLINT (clang-analyzer-optin.performance.Padding)
     /* Cell sizes for static load balancing, first index cartesian */
     real **slb_frac = nullptr;
 
+    /**< Information about the simulated system */
+    DDSystemInfo systemInfo;
+
     /* The width of the communicated boundaries */
     /**< Cut-off for multi-body interactions, also 2-body bonded when \p cutoff_mody > \p cutoff */
     real     cutoff_mbody = 0;
-    /**< Cut-off for non-bonded/2-body interactions */
-    real     cutoff = 0;
     /**< The minimum guaranteed cell-size, Cartesian indexing */
     rvec     cellsize_min = { };
     /**< The minimum guaranteed cell-size with dlb=auto */
diff --git a/src/gromacs/domdec/domdec_setup.cpp b/src/gromacs/domdec/domdec_setup.cpp
index ac4c9ac158..2c5698b152 100644
--- a/src/gromacs/domdec/domdec_setup.cpp
+++ b/src/gromacs/domdec/domdec_setup.cpp
@@ -65,6 +65,8 @@
 #include "gromacs/utility/logger.h"
 #include "gromacs/utility/stringutil.h"
 
+#include "domdec_internal.h"
+
 /*! \brief Margin for setting up the DD grid */
 #define DD_GRID_MARGIN_PRES_SCALE 1.05
 
@@ -606,8 +608,7 @@ static real optimize_ncells(const gmx::MDLogger &mdlog,
                             const gmx_mtop_t *mtop,
                             const matrix box, const gmx_ddbox_t *ddbox,
                             const t_inputrec *ir,
-                            real cellsize_limit, real cutoff,
-                            const bool haveInterDomainBondeds,
+                            const DDSystemInfo &systemInfo,
                             ivec nc)
 {
     int      npp, npme, d, nmax;
@@ -615,7 +616,7 @@ static real optimize_ncells(const gmx::MDLogger &mdlog,
     real     limit;
     ivec     itry;
 
-    limit  = cellsize_limit;
+    limit  = systemInfo.cellsizeLimit;
 
     npp = nnodes_tot - npme_only;
     if (EEL_PME(ir->coulombtype))
@@ -627,7 +628,7 @@ static real optimize_ncells(const gmx::MDLogger &mdlog,
         npme = 0;
     }
 
-    if (haveInterDomainBondeds)
+    if (systemInfo.haveInterDomainBondeds)
     {
         /* If we can skip PBC for distance calculations in plain-C bondeds,
          * we can save some time (e.g. 3D DD with pbc=xyz).
@@ -705,7 +706,7 @@ static real optimize_ncells(const gmx::MDLogger &mdlog,
     itry[YY] = 1;
     itry[ZZ] = 1;
     clear_ivec(nc);
-    assign_factors(limit, cutoff, box, ddbox, mtop->natoms, ir, pbcdxr,
+    assign_factors(limit, systemInfo.cutoff, box, ddbox, mtop->natoms, ir, pbcdxr,
                    npme, div.size(), div.data(), mdiv.data(), itry, nc);
 
     return limit;
@@ -719,8 +720,7 @@ dd_choose_grid(const gmx::MDLogger &mdlog,
                const matrix box, const gmx_ddbox_t *ddbox,
                const int numPmeRanksRequested,
                const gmx_bool bDynLoadBal, const real dlb_scale,
-               const real cellsize_limit, const real cutoff_dd,
-               const bool haveInterDomainBondeds)
+               const DDSystemInfo &systemInfo)
 {
     DDSetup ddSetup;
 
@@ -796,8 +796,7 @@ dd_choose_grid(const gmx::MDLogger &mdlog,
             optimize_ncells(mdlog, cr->nnodes, ddSetup.numPmeRanks,
                             bDynLoadBal, dlb_scale,
                             mtop, box, ddbox, ir,
-                            cellsize_limit, cutoff_dd,
-                            haveInterDomainBondeds,
+                            systemInfo,
                             ddSetup.numDomains);
     }
 
diff --git a/src/gromacs/domdec/partition.cpp b/src/gromacs/domdec/partition.cpp
index 23e5b93941..6cf0972984 100644
--- a/src/gromacs/domdec/partition.cpp
+++ b/src/gromacs/domdec/partition.cpp
@@ -282,10 +282,10 @@ static void dd_move_cellx(gmx_domdec_t      *dd,
                     {
                         c = 0;
                     }
-                    real det = (1 + c*c)*comm->cutoff*comm->cutoff - dist_d*dist_d;
+                    real det = (1 + c*c)*gmx::square(comm->systemInfo.cutoff) - dist_d*dist_d;
                     if (det > 0)
                     {
-                        dh[d1] = comm->cutoff - (c*dist_d + std::sqrt(det))/(1 + c*c);
+                        dh[d1] = comm->systemInfo.cutoff - (c*dist_d + std::sqrt(det))/(1 + c*c);
                     }
                     else
                     {
@@ -823,7 +823,7 @@ static void comm_dd_ns_cell_sizes(gmx_domdec_t *dd,
         dd_move_cellx(dd, ddbox, cell_ns_x0, cell_ns_x1);
         if (isDlbOn(dd->comm) && dd->ndim > 1)
         {
-            check_grid_jump(step, dd, dd->comm->cutoff, ddbox, TRUE);
+            check_grid_jump(step, dd, dd->comm->systemInfo.cutoff, ddbox, TRUE);
         }
     }
 }
@@ -1916,12 +1916,12 @@ static void setup_dd_communication(gmx_domdec_t *dd,
     bBondComm = comm->bBondComm;
 
     /* Do we need to determine extra distances for multi-body bondeds? */
-    bDistMB = (comm->haveInterDomainMultiBodyBondeds && isDlbOn(dd->comm) && dd->ndim > 1);
+    bDistMB = (comm->systemInfo.haveInterDomainMultiBodyBondeds && isDlbOn(dd->comm) && dd->ndim > 1);
 
     /* Do we need to determine extra distances for only two-body bondeds? */
     bDist2B = (bBondComm && !bDistMB);
 
-    const real r_comm2  = gmx::square(domainToDomainIntoAtomToDomainCutoff(*comm, comm->cutoff));
+    const real r_comm2  = gmx::square(domainToDomainIntoAtomToDomainCutoff(*comm, comm->systemInfo.cutoff));
     const real r_bcomm2 = gmx::square(domainToDomainIntoAtomToDomainCutoff(*comm, comm->cutoff_mbody));
 
     if (debug)
@@ -2296,7 +2296,9 @@ static void set_zones_size(gmx_domdec_t *dd,
     zones = &comm->zones;
 
     /* Do we need to determine extra distances for multi-body bondeds? */
-    bDistMB = (comm->haveInterDomainMultiBodyBondeds && isDlbOn(dd->comm) && dd->ndim > 1);
+    bDistMB = (comm->systemInfo.haveInterDomainMultiBodyBondeds &&
+               isDlbOn(dd->comm) &&
+               dd->ndim > 1);
 
     for (z = zone_start; z < zone_end; z++)
     {
@@ -2331,7 +2333,7 @@ static void set_zones_size(gmx_domdec_t *dd,
             }
         }
 
-        rcs   = comm->cutoff;
+        rcs   = comm->systemInfo.cutoff;
         rcmbs = comm->cutoff_mbody;
         if (ddbox->tric_dir[dim])
         {
-- 
2.22.0