Remove unused thole polarization rfac parameter
[alexxy/gromacs.git] / src / gromacs / fileio / tpxio.cpp
index 801174e5e55f312f5f50c5bb489a3336350ef257..f8b0ced58defbeb726d921d29b5b9480923a4e01 100644 (file)
@@ -3,7 +3,8 @@
  *
  * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
  * Copyright (c) 2001-2004, The GROMACS development team.
- * Copyright (c) 2013,2014,2015,2016,2017,2018,2019, by the GROMACS development team, led by
+ * Copyright (c) 2013,2014,2015,2016,2017 by the GROMACS development team.
+ * Copyright (c) 2018,2019,2020,2021, by the GROMACS development team, led by
  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
  * and including many others, as listed in the AUTHORS file in the
  * top-level source directory and at http://www.gromacs.org.
@@ -38,7 +39,7 @@
 
 /* This file is completely threadsafe - keep it that way! */
 
-#include "tpxio.h"
+#include "gromacs/fileio/tpxio.h"
 
 #include <cstdio>
 #include <cstdlib>
@@ -48,6 +49,7 @@
 #include <memory>
 #include <vector>
 
+#include "gromacs/applied_forces/awh/read_params.h"
 #include "gromacs/fileio/filetypes.h"
 #include "gromacs/fileio/gmxfio.h"
 #include "gromacs/fileio/gmxfio_xdr.h"
@@ -57,6 +59,7 @@
 #include "gromacs/mdtypes/awh_params.h"
 #include "gromacs/mdtypes/inputrec.h"
 #include "gromacs/mdtypes/md_enums.h"
+#include "gromacs/mdtypes/multipletimestepping.h"
 #include "gromacs/mdtypes/pull_params.h"
 #include "gromacs/mdtypes/state.h"
 #include "gromacs/pbcutil/boxutilities.h"
@@ -73,6 +76,7 @@
 #include "gromacs/utility/futil.h"
 #include "gromacs/utility/gmxassert.h"
 #include "gromacs/utility/inmemoryserializer.h"
+#include "gromacs/utility/iserializer.h"
 #include "gromacs/utility/keyvaluetreebuilder.h"
 #include "gromacs/utility/keyvaluetreeserializer.h"
 #include "gromacs/utility/smalloc.h"
@@ -91,7 +95,7 @@
  * merging with mainstream GROMACS, set this tag string back to
  * TPX_TAG_RELEASE, and instead add an element to tpxv.
  */
-static const char* tpx_tag = TPX_TAG_RELEASE;
+static const std::string tpx_tag = TPX_TAG_RELEASE;
 
 /*! \brief Enum of values that describe the contents of a tpr file
  * whose format matches a version number
@@ -129,7 +133,15 @@ enum tpxv
     tpxv_GenericInternalParameters, /**< Added internal parameters for mdrun modules*/
     tpxv_VSite2FD,                  /**< Added 2FD type virtual site */
     tpxv_AddSizeField, /**< Added field with information about the size of the serialized tpr file in bytes, excluding the header */
-    tpxv_Count         /**< the total number of tpxv versions */
+    tpxv_StoreNonBondedInteractionExclusionGroup, /**< Store the non bonded interaction exclusion group in the topology */
+    tpxv_VSite1,                                  /**< Added 1 type virtual site */
+    tpxv_MTS,                                     /**< Added multiple time stepping */
+    tpxv_RemovedConstantAcceleration, /**< Removed support for constant acceleration NEMD. */
+    tpxv_TransformationPullCoord,     /**< Support for transformation pull coordinates */
+    tpxv_SoftcoreGapsys,              /**< Added gapsys softcore function */
+    tpxv_ReaddedConstantAcceleration, /**< Re-added support for constant acceleration NEMD. */
+    tpxv_RemoveTholeRfac,             /**< Remove unused rfac parameter from thole listed force */
+    tpxv_Count                        /**< the total number of tpxv versions */
 };
 
 /*! \brief Version number of the file format written to run input
@@ -146,8 +158,13 @@ enum tpxv
 static const int tpx_version = tpxv_Count - 1;
 
 
-/* This number should only be increased when you edit the TOPOLOGY section
- * or the HEADER of the tpx format.
+/*! \brief
+ * Enum keeping track of incompatible changes for older TPR versions.
+ *
+ * The enum should be updated with a new field when editing the TOPOLOGY
+ * or HEADER of the tpx format. In particular, updating ftupd or
+ * changing the fields of TprHeaderVersion often trigger such needs.
+ *
  * This way we can maintain forward compatibility too for all analysis tools
  * and/or external programs that only need to know the atom/residue names,
  * charges, and bond connectivity.
@@ -158,10 +175,17 @@ static const int tpx_version = tpxv_Count - 1;
  *
  * In particular, it must be increased when adding new elements to
  * ftupd, so that old code can read new .tpr files.
- *
- * Updated for added field that contains the number of bytes of the tpr body, excluding the header.
  */
-static const int tpx_generation = 27;
+enum class TpxGeneration : int
+{
+    Initial = 26, //! First version is 26
+    AddSizeField, //! TPR header modified for writing as a block.
+    AddVSite1,    //! ftupd changed to include VSite1 type.
+    Count         //! Number of entries.
+};
+
+//! Value of Current TPR generation.
+static const int tpx_generation = static_cast<int>(TpxGeneration::Count) - 1;
 
 /* This number should be the most recent backwards incompatible version
  * I.e., if this number is 9, we cannot read tpx version 9 with this code.
@@ -189,6 +213,9 @@ typedef struct
  * obsolete t_interaction_function types. Any data read from such
  * fields is discarded. Their names have _NOLONGERUSED appended to
  * them to make things clear.
+ *
+ * When adding to or making breaking changes to reading this struct,
+ * update TpxGeneration.
  */
 static const t_ftupd ftupd[] = {
     { 70, F_RESTRBONDS },
@@ -203,10 +230,13 @@ static const t_ftupd ftupd[] = {
     { 72, F_GBPOL_NOLONGERUSED },
     { 72, F_NPSOLVATION_NOLONGERUSED },
     { 93, F_LJ_RECIP },
+    { 76, F_ANHARM_POL },
     { 90, F_FBPOSRES },
+    { tpxv_VSite1, F_VSITE1 },
+    { tpxv_VSite2FD, F_VSITE2FD },
+    { tpxv_GenericInternalParameters, F_DENSITYFITTING },
     { 69, F_VTEMP_NOLONGERUSED },
     { 66, F_PDISPCORR },
-    { 76, F_ANHARM_POL },
     { 79, F_DVDL_COUL },
     {
             79,
@@ -218,14 +248,9 @@ static const t_ftupd ftupd[] = {
     },
     { 79, F_DVDL_RESTRAINT },
     { 79, F_DVDL_TEMPERATURE },
-    { tpxv_GenericInternalParameters, F_DENSITYFITTING },
-    { tpxv_VSite2FD, F_VSITE2FD },
 };
 #define NFTUPD asize(ftupd)
 
-/* Needed for backward compatibility */
-#define MAXNODES 256
-
 /**************************************************************
  *
  * Now the higer level routines that do io of the structures and arrays
@@ -235,20 +260,16 @@ static void do_pullgrp_tpx_pre95(gmx::ISerializer* serializer, t_pull_group* pgr
 {
     rvec tmp;
 
-    serializer->doInt(&pgrp->nat);
-    if (serializer->reading())
-    {
-        snew(pgrp->ind, pgrp->nat);
-    }
-    serializer->doIntArray(pgrp->ind, pgrp->nat);
-    serializer->doInt(&pgrp->nweight);
-    if (serializer->reading())
-    {
-        snew(pgrp->weight, pgrp->nweight);
-    }
-    serializer->doRealArray(pgrp->weight, pgrp->nweight);
+    int numAtoms = pgrp->ind.size();
+    serializer->doInt(&numAtoms);
+    pgrp->ind.resize(numAtoms);
+    serializer->doIntArray(pgrp->ind.data(), numAtoms);
+    int numWeights = pgrp->weight.size();
+    serializer->doInt(&numWeights);
+    pgrp->weight.resize(numWeights);
+    serializer->doRealArray(pgrp->weight.data(), numWeights);
     serializer->doInt(&pgrp->pbcatom);
-    serializer->doRvec(&pcrd->vec);
+    serializer->doRvec(&pcrd->vec.as_vec());
     clear_rvec(pcrd->origin);
     serializer->doRvec(&tmp);
     pcrd->init = tmp[0];
@@ -259,68 +280,54 @@ static void do_pullgrp_tpx_pre95(gmx::ISerializer* serializer, t_pull_group* pgr
 
 static void do_pull_group(gmx::ISerializer* serializer, t_pull_group* pgrp)
 {
-    serializer->doInt(&pgrp->nat);
-    if (serializer->reading())
-    {
-        snew(pgrp->ind, pgrp->nat);
-    }
-    serializer->doIntArray(pgrp->ind, pgrp->nat);
-    serializer->doInt(&pgrp->nweight);
-    if (serializer->reading())
-    {
-        snew(pgrp->weight, pgrp->nweight);
-    }
-    serializer->doRealArray(pgrp->weight, pgrp->nweight);
+    int numAtoms = pgrp->ind.size();
+    serializer->doInt(&numAtoms);
+    pgrp->ind.resize(numAtoms);
+    serializer->doIntArray(pgrp->ind.data(), numAtoms);
+    int numWeights = pgrp->weight.size();
+    serializer->doInt(&numWeights);
+    pgrp->weight.resize(numWeights);
+    serializer->doRealArray(pgrp->weight.data(), numWeights);
     serializer->doInt(&pgrp->pbcatom);
 }
 
 static void do_pull_coord(gmx::ISerializer* serializer,
                           t_pull_coord*     pcrd,
                           int               file_version,
-                          int               ePullOld,
-                          int               eGeomOld,
+                          PullingAlgorithm  ePullOld,
+                          PullGroupGeometry eGeomOld,
                           ivec              dimOld)
 {
     if (file_version >= tpxv_PullCoordNGroup)
     {
-        serializer->doInt(&pcrd->eType);
+        serializer->doEnumAsInt(&pcrd->eType);
         if (file_version >= tpxv_PullExternalPotential)
         {
-            if (pcrd->eType == epullEXTERNAL)
+            if (pcrd->eType == PullingAlgorithm::External)
             {
-                std::string buf;
-                if (serializer->reading())
-                {
-                    serializer->doString(&buf);
-                    pcrd->externalPotentialProvider = gmx_strdup(buf.c_str());
-                }
-                else
-                {
-                    buf = pcrd->externalPotentialProvider;
-                    serializer->doString(&buf);
-                }
+                serializer->doString(&pcrd->externalPotentialProvider);
             }
             else
             {
-                pcrd->externalPotentialProvider = nullptr;
+                pcrd->externalPotentialProvider.clear();
             }
         }
         else
         {
             if (serializer->reading())
             {
-                pcrd->externalPotentialProvider = nullptr;
+                pcrd->externalPotentialProvider.clear();
             }
         }
         /* Note that we try to support adding new geometries without
          * changing the tpx version. This requires checks when printing the
          * geometry string and a check and fatal_error in init_pull.
          */
-        serializer->doInt(&pcrd->eGeom);
+        serializer->doEnumAsInt(&pcrd->eGeom);
         serializer->doInt(&pcrd->ngroup);
         if (pcrd->ngroup <= c_pullCoordNgroupMax)
         {
-            serializer->doIntArray(pcrd->group, pcrd->ngroup);
+            serializer->doIntArray(pcrd->group.data(), pcrd->ngroup);
         }
         else
         {
@@ -336,7 +343,18 @@ static void do_pull_coord(gmx::ISerializer* serializer,
 
             pcrd->ngroup = 0;
         }
-        serializer->doIvec(&pcrd->dim);
+        serializer->doIvec(&pcrd->dim.as_vec());
+        if (file_version >= tpxv_TransformationPullCoord)
+        {
+            serializer->doString(&pcrd->expression);
+        }
+        else
+        {
+            if (serializer->reading())
+            {
+                pcrd->expression.clear();
+            }
+        }
     }
     else
     {
@@ -345,15 +363,15 @@ static void do_pull_coord(gmx::ISerializer* serializer,
         serializer->doInt(&pcrd->group[1]);
         if (file_version >= tpxv_PullCoordTypeGeom)
         {
-            pcrd->ngroup = (pcrd->eGeom == epullgDIRRELATIVE ? 4 : 2);
-            serializer->doInt(&pcrd->eType);
-            serializer->doInt(&pcrd->eGeom);
+            pcrd->ngroup = (pcrd->eGeom == PullGroupGeometry::DirectionRelative ? 4 : 2);
+            serializer->doEnumAsInt(&pcrd->eType);
+            serializer->doEnumAsInt(&pcrd->eGeom);
             if (pcrd->ngroup == 4)
             {
                 serializer->doInt(&pcrd->group[2]);
                 serializer->doInt(&pcrd->group[3]);
             }
-            serializer->doIvec(&pcrd->dim);
+            serializer->doIvec(&pcrd->dim.as_vec());
         }
         else
         {
@@ -362,8 +380,8 @@ static void do_pull_coord(gmx::ISerializer* serializer,
             copy_ivec(dimOld, pcrd->dim);
         }
     }
-    serializer->doRvec(&pcrd->origin);
-    serializer->doRvec(&pcrd->vec);
+    serializer->doRvec(&pcrd->origin.as_vec());
+    serializer->doRvec(&pcrd->vec.as_vec());
     if (file_version >= tpxv_PullCoordTypeGeom)
     {
         serializer->doBool(&pcrd->bStart);
@@ -390,17 +408,14 @@ static void do_expandedvals(gmx::ISerializer* serializer, t_expanded* expand, t_
     {
         if (n_lambda > 0)
         {
-            if (serializer->reading())
-            {
-                snew(expand->init_lambda_weights, n_lambda);
-            }
-            serializer->doRealArray(expand->init_lambda_weights, n_lambda);
+            expand->init_lambda_weights.resize(n_lambda);
+            serializer->doRealArray(expand->init_lambda_weights.data(), n_lambda);
             serializer->doBool(&expand->bInit_weights);
         }
 
         serializer->doInt(&expand->nstexpanded);
-        serializer->doInt(&expand->elmcmove);
-        serializer->doInt(&expand->elamstats);
+        serializer->doEnumAsInt(&expand->elmcmove);
+        serializer->doEnumAsInt(&expand->elamstats);
         serializer->doInt(&expand->lmc_repeats);
         serializer->doInt(&expand->gibbsdeltalam);
         serializer->doInt(&expand->lmc_forced_nstart);
@@ -414,7 +429,7 @@ static void do_expandedvals(gmx::ISerializer* serializer, t_expanded* expand, t_
         serializer->doReal(&expand->wl_ratio);
         serializer->doReal(&expand->init_wl_delta);
         serializer->doBool(&expand->bWLoneovert);
-        serializer->doInt(&expand->elmceq);
+        serializer->doEnumAsInt(&expand->elmceq);
         serializer->doInt(&expand->equil_steps);
         serializer->doInt(&expand->equil_samples);
         serializer->doInt(&expand->equil_n_at_lam);
@@ -427,16 +442,16 @@ static void do_simtempvals(gmx::ISerializer* serializer, t_simtemp* simtemp, int
 {
     if (file_version >= 79)
     {
-        serializer->doInt(&simtemp->eSimTempScale);
+        serializer->doEnumAsInt(&simtemp->eSimTempScale);
         serializer->doReal(&simtemp->simtemp_high);
         serializer->doReal(&simtemp->simtemp_low);
         if (n_lambda > 0)
         {
             if (serializer->reading())
             {
-                snew(simtemp->temperatures, n_lambda);
+                simtemp->temperatures.resize(n_lambda);
             }
-            serializer->doRealArray(simtemp->temperatures, n_lambda);
+            serializer->doRealArray(simtemp->temperatures.data(), n_lambda);
         }
     }
 }
@@ -454,7 +469,6 @@ static void do_imd(gmx::ISerializer* serializer, t_IMD* imd)
 static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file_version)
 {
     /* i is defined in the ndo_double macro; use g to iterate. */
-    int  g;
     real rdum;
 
     /* free energy values */
@@ -480,24 +494,17 @@ static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file
     if (file_version >= 79)
     {
         serializer->doInt(&fepvals->n_lambda);
-        if (serializer->reading())
-        {
-            snew(fepvals->all_lambda, efptNR);
-        }
-        for (g = 0; g < efptNR; g++)
+        for (auto g : keysOf(fepvals->all_lambda))
         {
             if (fepvals->n_lambda > 0)
             {
-                if (serializer->reading())
-                {
-                    snew(fepvals->all_lambda[g], fepvals->n_lambda);
-                }
-                serializer->doDoubleArray(fepvals->all_lambda[g], fepvals->n_lambda);
-                serializer->doBoolArray(fepvals->separate_dvdl, efptNR);
+                fepvals->all_lambda[g].resize(fepvals->n_lambda);
+                serializer->doDoubleArray(fepvals->all_lambda[g].data(), fepvals->n_lambda);
+                serializer->doBoolArray(fepvals->separate_dvdl.begin(), fepvals->separate_dvdl.size());
             }
             else if (fepvals->init_lambda >= 0)
             {
-                fepvals->separate_dvdl[efptFEP] = TRUE;
+                fepvals->separate_dvdl[FreeEnergyPerturbationCouplingType::Fep] = TRUE;
             }
         }
     }
@@ -506,36 +513,33 @@ static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file
         serializer->doInt(&fepvals->n_lambda);
         if (serializer->reading())
         {
-            int g;
-
-            snew(fepvals->all_lambda, efptNR);
             /* still allocate the all_lambda array's contents. */
-            for (g = 0; g < efptNR; g++)
+            for (auto g : keysOf(fepvals->all_lambda))
             {
                 if (fepvals->n_lambda > 0)
                 {
-                    snew(fepvals->all_lambda[g], fepvals->n_lambda);
+                    fepvals->all_lambda[g].resize(fepvals->n_lambda);
                 }
             }
         }
-        serializer->doDoubleArray(fepvals->all_lambda[efptFEP], fepvals->n_lambda);
+        serializer->doDoubleArray(fepvals->all_lambda[FreeEnergyPerturbationCouplingType::Fep].data(),
+                                  fepvals->n_lambda);
         if (fepvals->init_lambda >= 0)
         {
-            int g, h;
-
-            fepvals->separate_dvdl[efptFEP] = TRUE;
+            fepvals->separate_dvdl[FreeEnergyPerturbationCouplingType::Fep] = TRUE;
 
             if (serializer->reading())
             {
                 /* copy the contents of the efptFEP lambda component to all
                    the other components */
-                for (g = 0; g < efptNR; g++)
+                for (auto g : keysOf(fepvals->all_lambda))
                 {
-                    for (h = 0; h < fepvals->n_lambda; h++)
+                    for (int h = 0; h < fepvals->n_lambda; h++)
                     {
-                        if (g != efptFEP)
+                        if (g != FreeEnergyPerturbationCouplingType::Fep)
                         {
-                            fepvals->all_lambda[g][h] = fepvals->all_lambda[efptFEP][h];
+                            fepvals->all_lambda[g][h] =
+                                    fepvals->all_lambda[FreeEnergyPerturbationCouplingType::Fep][h];
                         }
                     }
                 }
@@ -544,11 +548,10 @@ static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file
     }
     else
     {
-        fepvals->n_lambda   = 0;
-        fepvals->all_lambda = nullptr;
+        fepvals->n_lambda = 0;
         if (fepvals->init_lambda >= 0)
         {
-            fepvals->separate_dvdl[efptFEP] = TRUE;
+            fepvals->separate_dvdl[FreeEnergyPerturbationCouplingType::Fep] = TRUE;
         }
     }
     serializer->doReal(&fepvals->sc_alpha);
@@ -561,6 +564,10 @@ static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file
     {
         fepvals->sc_r_power = 6.0;
     }
+    if (fepvals->sc_r_power != 6.0)
+    {
+        gmx_fatal(FARGS, "sc-r-power=48 is no longer supported");
+    }
     serializer->doReal(&fepvals->sc_sigma);
     if (serializer->reading())
     {
@@ -592,13 +599,13 @@ static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file
 
     if (file_version >= 73)
     {
-        serializer->doInt(&fepvals->separate_dhdl_file);
-        serializer->doInt(&fepvals->dhdl_derivatives);
+        serializer->doEnumAsInt(&fepvals->separate_dhdl_file);
+        serializer->doEnumAsInt(&fepvals->dhdl_derivatives);
     }
     else
     {
-        fepvals->separate_dhdl_file = esepdhdlfileYES;
-        fepvals->dhdl_derivatives   = edhdlderivativesYES;
+        fepvals->separate_dhdl_file = SeparateDhdlFile::Yes;
+        fepvals->dhdl_derivatives   = DhDlDerivativeCalculation::Yes;
     }
     if (file_version >= 71)
     {
@@ -612,11 +619,25 @@ static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file
     }
     if (file_version >= 79)
     {
-        serializer->doInt(&fepvals->edHdLPrintEnergy);
+        serializer->doEnumAsInt(&fepvals->edHdLPrintEnergy);
     }
     else
     {
-        fepvals->edHdLPrintEnergy = edHdLPrintEnergyNO;
+        fepvals->edHdLPrintEnergy = FreeEnergyPrintEnergy::No;
+    }
+    if (file_version >= tpxv_SoftcoreGapsys)
+    {
+        serializer->doInt(reinterpret_cast<int*>(&fepvals->softcoreFunction));
+        serializer->doReal(&fepvals->scGapsysScaleLinpointLJ);
+        serializer->doReal(&fepvals->scGapsysScaleLinpointQ);
+        serializer->doReal(&fepvals->scGapsysSigmaLJ);
+    }
+    else
+    {
+        fepvals->softcoreFunction        = SoftcoreType::Beutler;
+        fepvals->scGapsysScaleLinpointLJ = 0.85;
+        fepvals->scGapsysScaleLinpointQ  = 0.3;
+        fepvals->scGapsysSigmaLJ         = 0.3;
     }
 
     /* handle lambda_neighbors */
@@ -650,68 +671,11 @@ static void do_fepvals(gmx::ISerializer* serializer, t_lambda* fepvals, int file
     }
 }
 
-static void do_awhBias(gmx::ISerializer* serializer, gmx::AwhBiasParams* awhBiasParams, int gmx_unused file_version)
-{
-    serializer->doInt(&awhBiasParams->eTarget);
-    serializer->doDouble(&awhBiasParams->targetBetaScaling);
-    serializer->doDouble(&awhBiasParams->targetCutoff);
-    serializer->doInt(&awhBiasParams->eGrowth);
-    serializer->doInt(&awhBiasParams->bUserData);
-    serializer->doDouble(&awhBiasParams->errorInitial);
-    serializer->doInt(&awhBiasParams->ndim);
-    serializer->doInt(&awhBiasParams->shareGroup);
-    serializer->doBool(&awhBiasParams->equilibrateHistogram);
-
-    if (serializer->reading())
-    {
-        snew(awhBiasParams->dimParams, awhBiasParams->ndim);
-    }
-
-    for (int d = 0; d < awhBiasParams->ndim; d++)
-    {
-        gmx::AwhDimParams* dimParams = &awhBiasParams->dimParams[d];
-
-        serializer->doInt(&dimParams->eCoordProvider);
-        serializer->doInt(&dimParams->coordIndex);
-        serializer->doDouble(&dimParams->origin);
-        serializer->doDouble(&dimParams->end);
-        serializer->doDouble(&dimParams->period);
-        serializer->doDouble(&dimParams->forceConstant);
-        serializer->doDouble(&dimParams->diffusion);
-        serializer->doDouble(&dimParams->coordValueInit);
-        serializer->doDouble(&dimParams->coverDiameter);
-    }
-}
-
-static void do_awh(gmx::ISerializer* serializer, gmx::AwhParams* awhParams, int gmx_unused file_version)
+static void do_pull(gmx::ISerializer* serializer, pull_params_t* pull, int file_version, PullingAlgorithm ePullOld)
 {
-    serializer->doInt(&awhParams->numBias);
-    serializer->doInt(&awhParams->nstOut);
-    serializer->doInt64(&awhParams->seed);
-    serializer->doInt(&awhParams->nstSampleCoord);
-    serializer->doInt(&awhParams->numSamplesUpdateFreeEnergy);
-    serializer->doInt(&awhParams->ePotential);
-    serializer->doBool(&awhParams->shareBiasMultisim);
-
-    if (awhParams->numBias > 0)
-    {
-        if (serializer->reading())
-        {
-            snew(awhParams->awhBiasParams, awhParams->numBias);
-        }
-
-        for (int k = 0; k < awhParams->numBias; k++)
-        {
-            do_awhBias(serializer, &awhParams->awhBiasParams[k], file_version);
-        }
-    }
-}
-
-static void do_pull(gmx::ISerializer* serializer, pull_params_t* pull, int file_version, int ePullOld)
-{
-    int  eGeomOld = -1;
-    ivec dimOld;
-    int  g;
+    PullGroupGeometry eGeomOld = PullGroupGeometry::Count;
+    ivec              dimOld;
+    int               g;
 
     if (file_version >= 95)
     {
@@ -726,7 +690,7 @@ static void do_pull(gmx::ISerializer* serializer, pull_params_t* pull, int file_
     {
         real dum;
 
-        serializer->doInt(&eGeomOld);
+        serializer->doEnumAsInt(&eGeomOld);
         serializer->doIvec(&dimOld);
         /* The inner cylinder radius, now removed */
         serializer->doReal(&dum);
@@ -765,21 +729,30 @@ static void do_pull(gmx::ISerializer* serializer, pull_params_t* pull, int file_
     {
         pull->bSetPbcRefToPrevStepCOM = FALSE;
     }
-    if (serializer->reading())
-    {
-        snew(pull->group, pull->ngroup);
-        snew(pull->coord, pull->ncoord);
-    }
+    pull->group.resize(pull->ngroup);
+    pull->coord.resize(pull->ncoord);
     if (file_version < 95)
     {
         /* epullgPOS for position pulling, before epullgDIRPBC was removed */
-        if (eGeomOld == epullgDIRPBC)
+        if (eGeomOld == PullGroupGeometry::DirectionPBC)
         {
             gmx_fatal(FARGS, "pull-geometry=position is no longer supported");
         }
-        if (eGeomOld > epullgDIRPBC)
+        if (eGeomOld > PullGroupGeometry::DirectionPBC)
         {
-            eGeomOld -= 1;
+            switch (eGeomOld)
+            {
+                case (PullGroupGeometry::DirectionRelative):
+                    eGeomOld = PullGroupGeometry::DirectionPBC;
+                    break;
+                case (PullGroupGeometry::Angle):
+                    eGeomOld = PullGroupGeometry::DirectionRelative;
+                    break;
+                case (PullGroupGeometry::Dihedral): eGeomOld = PullGroupGeometry::Angle; break;
+                case (PullGroupGeometry::AngleAxis): eGeomOld = PullGroupGeometry::Dihedral; break;
+                case (PullGroupGeometry::Count): eGeomOld = PullGroupGeometry::AngleAxis; break;
+                default: GMX_RELEASE_ASSERT(false, "Unhandled old pull type");
+            }
         }
 
         for (g = 0; g < pull->ngroup; g++)
@@ -793,7 +766,7 @@ static void do_pull(gmx::ISerializer* serializer, pull_params_t* pull, int file_
             }
         }
 
-        pull->bPrintCOM = (pull->group[0].nat > 0);
+        pull->bPrintCOM = (!pull->group[0].ind.empty());
     }
     else
     {
@@ -804,6 +777,10 @@ static void do_pull(gmx::ISerializer* serializer, pull_params_t* pull, int file_
         for (g = 0; g < pull->ncoord; g++)
         {
             do_pull_coord(serializer, &pull->coord[g], file_version, ePullOld, eGeomOld, dimOld);
+            if (serializer->reading())
+            {
+                pull->coord[g].coordIndex = g;
+            }
         }
     }
     if (file_version >= tpxv_PullAverage)
@@ -822,8 +799,18 @@ static void do_pull(gmx::ISerializer* serializer, pull_params_t* pull, int file_
 
 static void do_rotgrp(gmx::ISerializer* serializer, t_rotgrp* rotg)
 {
-    serializer->doInt(&rotg->eType);
-    serializer->doInt(&rotg->bMassW);
+    serializer->doEnumAsInt(&rotg->eType);
+    if (serializer->reading())
+    {
+        int temp = 0;
+        serializer->doInt(&temp);
+        rotg->bMassW = static_cast<bool>(temp);
+    }
+    else
+    {
+        int temp = static_cast<int>(rotg->bMassW);
+        serializer->doInt(&temp);
+    }
     serializer->doInt(&rotg->nat);
     if (serializer->reading())
     {
@@ -842,7 +829,7 @@ static void do_rotgrp(gmx::ISerializer* serializer, t_rotgrp* rotg)
     serializer->doReal(&rotg->slab_dist);
     serializer->doReal(&rotg->min_gaussian);
     serializer->doReal(&rotg->eps);
-    serializer->doInt(&rotg->eFittype);
+    serializer->doEnumAsInt(&rotg->eFittype);
     serializer->doInt(&rotg->PotAngle_nstep);
     serializer->doReal(&rotg->PotAngle_step);
 }
@@ -892,7 +879,7 @@ static void do_swapgroup(gmx::ISerializer* serializer, t_swapGroup* g)
     serializer->doIntArray(g->ind, g->nat);
 
     /* Requested counts for compartments A and B */
-    serializer->doIntArray(g->nmolReq, eCompNR);
+    serializer->doIntArray(g->nmolReq.data(), static_cast<int>(Compartment::Count));
 }
 
 static void do_swapcoords_tpx(gmx::ISerializer* serializer, t_swapcoords* swap, int file_version)
@@ -944,17 +931,18 @@ static void do_swapcoords_tpx(gmx::ISerializer* serializer, t_swapcoords* swap,
         swap->ngrp = 5;
         snew(swap->grp, swap->ngrp);
 
-        swap->grp[eGrpSplit0].molname  = gmx_strdup("split0");  // group 0: split0
-        swap->grp[eGrpSplit1].molname  = gmx_strdup("split1");  // group 1: split1
-        swap->grp[eGrpSolvent].molname = gmx_strdup("solvent"); // group 2: solvent
-        swap->grp[3].molname           = gmx_strdup("anions");  // group 3: anions
-        swap->grp[4].molname           = gmx_strdup("cations"); // group 4: cations
+        swap->grp[static_cast<int>(SwapGroupSplittingType::Split0)].molname = gmx_strdup("split0"); // group 0: split0
+        swap->grp[static_cast<int>(SwapGroupSplittingType::Split1)].molname = gmx_strdup("split1"); // group 1: split1
+        swap->grp[static_cast<int>(SwapGroupSplittingType::Solvent)].molname =
+                gmx_strdup("solvent");                // group 2: solvent
+        swap->grp[3].molname = gmx_strdup("anions");  // group 3: anions
+        swap->grp[4].molname = gmx_strdup("cations"); // group 4: cations
 
         serializer->doInt(&swap->grp[3].nat);
-        serializer->doInt(&swap->grp[eGrpSolvent].nat);
-        serializer->doInt(&swap->grp[eGrpSplit0].nat);
+        serializer->doInt(&swap->grp[static_cast<int>(SwapGroupSplittingType::Solvent)].nat);
+        serializer->doInt(&swap->grp[static_cast<int>(SwapGroupSplittingType::Split0)].nat);
         serializer->doBool(&swap->massw_split[eChannel0]);
-        serializer->doInt(&swap->grp[eGrpSplit1].nat);
+        serializer->doInt(&swap->grp[static_cast<int>(SwapGroupSplittingType::Split1)].nat);
         serializer->doBool(&swap->massw_split[eChannel1]);
         serializer->doInt(&swap->nstswap);
         serializer->doInt(&swap->nAverage);
@@ -969,7 +957,10 @@ static void do_swapcoords_tpx(gmx::ISerializer* serializer, t_swapcoords* swap,
         // The order[] array keeps compatibility with older .tpr files
         // by reading in the groups in the classic order
         {
-            const int order[4] = { 3, eGrpSolvent, eGrpSplit0, eGrpSplit1 };
+            const int order[4] = { 3,
+                                   static_cast<int>(SwapGroupSplittingType::Solvent),
+                                   static_cast<int>(SwapGroupSplittingType::Split0),
+                                   static_cast<int>(SwapGroupSplittingType::Split1) };
 
             for (int ig = 0; ig < 4; ig++)
             {
@@ -1051,7 +1042,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     gmx::KeyValueTreeObjectBuilder paramsObj = paramsBuilder.rootObject();
 
     /* Basic inputrec stuff */
-    serializer->doInt(&ir->eI);
+    serializer->doEnumAsInt(&ir->eI);
     if (file_version >= 62)
     {
         serializer->doInt64(&ir->nsteps);
@@ -1074,6 +1065,29 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
 
     serializer->doInt(&ir->simulation_part);
 
+    if (file_version >= tpxv_MTS)
+    {
+        serializer->doBool(&ir->useMts);
+        int numLevels = ir->mtsLevels.size();
+        if (ir->useMts)
+        {
+            serializer->doInt(&numLevels);
+        }
+        ir->mtsLevels.resize(numLevels);
+        for (auto& mtsLevel : ir->mtsLevels)
+        {
+            int forceGroups = mtsLevel.forceGroups.to_ulong();
+            serializer->doInt(&forceGroups);
+            mtsLevel.forceGroups = std::bitset<static_cast<int>(gmx::MtsForceGroups::Count)>(forceGroups);
+            serializer->doInt(&mtsLevel.stepFactor);
+        }
+    }
+    else
+    {
+        ir->useMts = false;
+        ir->mtsLevels.clear();
+    }
+
     if (file_version >= 67)
     {
         serializer->doInt(&ir->nstcalcenergy);
@@ -1084,15 +1098,21 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     }
     if (file_version >= 81)
     {
-        serializer->doInt(&ir->cutoff_scheme);
+        serializer->doEnumAsInt(&ir->cutoff_scheme);
         if (file_version < 94)
         {
-            ir->cutoff_scheme = 1 - ir->cutoff_scheme;
+            // Need to invert the scheme order
+            switch (ir->cutoff_scheme)
+            {
+                case (CutoffScheme::Group): ir->cutoff_scheme = CutoffScheme::Verlet; break;
+                case (CutoffScheme::Verlet): ir->cutoff_scheme = CutoffScheme::Group; break;
+                default: GMX_RELEASE_ASSERT(false, "Unhandled cutoff scheme type");
+            }
         }
     }
     else
     {
-        ir->cutoff_scheme = ecutsGROUP;
+        ir->cutoff_scheme = CutoffScheme::Group;
     }
     serializer->doInt(&idum); /* used to be ns_type; not used anymore */
     serializer->doInt(&ir->nstlist);
@@ -1101,7 +1121,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     serializer->doReal(&ir->rtpi);
 
     serializer->doInt(&ir->nstcomm);
-    serializer->doInt(&ir->comm_mode);
+    serializer->doEnumAsInt(&ir->comm_mode);
 
     /* ignore nstcheckpoint */
     if (file_version < tpxv_RemoveObsoleteParameters1)
@@ -1150,20 +1170,14 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
             real dummy_rlistlong = -1;
             serializer->doReal(&dummy_rlistlong);
 
-            if (ir->rlist > 0 && (dummy_rlistlong == 0 || dummy_rlistlong > ir->rlist))
-            {
-                // Get mdrun to issue an error (regardless of
-                // ir->cutoff_scheme).
-                ir->useTwinRange = true;
-            }
-            else
-            {
-                // grompp used to set rlistlong actively. Users were
-                // probably also confused and set rlistlong == rlist.
-                // However, in all remaining cases, it is safe to let
-                // mdrun proceed normally.
-                ir->useTwinRange = false;
-            }
+            ir->useTwinRange = (ir->rlist > 0 && (dummy_rlistlong == 0 || dummy_rlistlong > ir->rlist));
+            // When true, this forces mdrun to issue an error (regardless of
+            // ir->cutoff_scheme).
+            //
+            // Otherwise, grompp used to set rlistlong actively. Users
+            // were probably also confused and set rlistlong == rlist.
+            // However, in all remaining cases, it is safe to let
+            // mdrun proceed normally.
         }
     }
     else
@@ -1179,29 +1193,31 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
         int dummy_nstcalclr = -1;
         serializer->doInt(&dummy_nstcalclr);
     }
-    serializer->doInt(&ir->coulombtype);
+    serializer->doEnumAsInt(&ir->coulombtype);
     if (file_version >= 81)
     {
-        serializer->doInt(&ir->coulomb_modifier);
+        serializer->doEnumAsInt(&ir->coulomb_modifier);
     }
     else
     {
-        ir->coulomb_modifier = (ir->cutoff_scheme == ecutsVERLET ? eintmodPOTSHIFT : eintmodNONE);
+        ir->coulomb_modifier = (ir->cutoff_scheme == CutoffScheme::Verlet ? InteractionModifiers::PotShift
+                                                                          : InteractionModifiers::None);
     }
     serializer->doReal(&ir->rcoulomb_switch);
     serializer->doReal(&ir->rcoulomb);
-    serializer->doInt(&ir->vdwtype);
+    serializer->doEnumAsInt(&ir->vdwtype);
     if (file_version >= 81)
     {
-        serializer->doInt(&ir->vdw_modifier);
+        serializer->doEnumAsInt(&ir->vdw_modifier);
     }
     else
     {
-        ir->vdw_modifier = (ir->cutoff_scheme == ecutsVERLET ? eintmodPOTSHIFT : eintmodNONE);
+        ir->vdw_modifier = (ir->cutoff_scheme == CutoffScheme::Verlet ? InteractionModifiers::PotShift
+                                                                      : InteractionModifiers::None);
     }
     serializer->doReal(&ir->rvdw_switch);
     serializer->doReal(&ir->rvdw);
-    serializer->doInt(&ir->eDispCorr);
+    serializer->doEnumAsInt(&ir->eDispCorr);
     serializer->doReal(&ir->epsilon_r);
     serializer->doReal(&ir->epsilon_rf);
     serializer->doReal(&ir->tabext);
@@ -1260,7 +1276,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     {
         ir->ewald_rtol_lj = ir->ewald_rtol;
     }
-    serializer->doInt(&ir->ewald_geometry);
+    serializer->doEnumAsInt(&ir->ewald_geometry);
     serializer->doReal(&ir->epsilon_surface);
 
     /* ignore bOptFFT */
@@ -1271,10 +1287,10 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
 
     if (file_version >= 93)
     {
-        serializer->doInt(&ir->ljpme_combination_rule);
+        serializer->doEnumAsInt(&ir->ljpme_combination_rule);
     }
     serializer->doBool(&ir->bContinuation);
-    serializer->doInt(&ir->etc);
+    serializer->doEnumAsInt(&ir->etc);
     /* before version 18, ir->etc was a gmx_bool (ir->btc),
      * but the values 0 and 1 still mean no and
      * berendsen temperature coupling, respectively.
@@ -1291,8 +1307,8 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     {
         ir->nsttcouple = ir->nstcalcenergy;
     }
-    serializer->doInt(&ir->epc);
-    serializer->doInt(&ir->epct);
+    serializer->doEnumAsInt(&ir->epc);
+    serializer->doEnumAsInt(&ir->epct);
     if (file_version >= 71)
     {
         serializer->doInt(&ir->nstpcouple);
@@ -1308,7 +1324,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     serializer->doRvec(&ir->compress[XX]);
     serializer->doRvec(&ir->compress[YY]);
     serializer->doRvec(&ir->compress[ZZ]);
-    serializer->doInt(&ir->refcoord_scaling);
+    serializer->doEnumAsInt(&ir->refcoord_scaling);
     serializer->doRvec(&ir->posres_com);
     serializer->doRvec(&ir->posres_comB);
 
@@ -1323,8 +1339,12 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
 
     serializer->doReal(&ir->shake_tol);
 
-    serializer->doInt(&ir->efep);
-    do_fepvals(serializer, ir->fepvals, file_version);
+    serializer->doEnumAsInt(&ir->efep);
+    if (serializer->reading())
+    {
+        ir->fepvals = std::make_unique<t_lambda>();
+    }
+    do_fepvals(serializer, ir->fepvals.get(), file_version);
 
     if (file_version >= 79)
     {
@@ -1340,28 +1360,28 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     }
     if (ir->bSimTemp)
     {
-        do_simtempvals(serializer, ir->simtempvals, ir->fepvals->n_lambda, file_version);
+        if (serializer->reading())
+        {
+            ir->simtempvals = std::make_unique<t_simtemp>();
+        }
+        do_simtempvals(serializer, ir->simtempvals.get(), ir->fepvals->n_lambda, file_version);
     }
 
     if (file_version >= 79)
     {
         serializer->doBool(&ir->bExpanded);
-        if (ir->bExpanded)
-        {
-            ir->bExpanded = TRUE;
-        }
-        else
-        {
-            ir->bExpanded = FALSE;
-        }
     }
     if (ir->bExpanded)
     {
-        do_expandedvals(serializer, ir->expandedvals, ir->fepvals, file_version);
+        if (serializer->reading())
+        {
+            ir->expandedvals = std::make_unique<t_expanded>();
+        }
+        do_expandedvals(serializer, ir->expandedvals.get(), ir->fepvals.get(), file_version);
     }
 
-    serializer->doInt(&ir->eDisre);
-    serializer->doInt(&ir->eDisreWeighting);
+    serializer->doEnumAsInt(&ir->eDisre);
+    serializer->doEnumAsInt(&ir->eDisreWeighting);
     serializer->doBool(&ir->bDisreMixed);
     serializer->doReal(&ir->dr_fc);
     serializer->doReal(&ir->dr_tau);
@@ -1381,7 +1401,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     serializer->doBool(&ir->bShakeSOR);
     serializer->doInt(&ir->niter);
     serializer->doReal(&ir->fc_stepsize);
-    serializer->doInt(&ir->eConstrAlg);
+    serializer->doEnumAsInt(&ir->eConstrAlg);
     serializer->doInt(&ir->nProjOrder);
     serializer->doReal(&ir->LincsWarnAngle);
     serializer->doInt(&ir->nLincsIter);
@@ -1452,7 +1472,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
 
     /* pull stuff */
     {
-        int ePullOld = 0;
+        PullingAlgorithm ePullOld = PullingAlgorithm::Umbrella;
 
         if (file_version >= tpxv_PullCoordTypeGeom)
         {
@@ -1460,18 +1480,36 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
         }
         else
         {
-            serializer->doInt(&ePullOld);
-            ir->bPull = (ePullOld > 0);
+            serializer->doEnumAsInt(&ePullOld);
+            ir->bPull = (ePullOld != PullingAlgorithm::Umbrella);
             /* We removed the first ePull=ePullNo for the enum */
-            ePullOld -= 1;
+            switch (ePullOld)
+            {
+                case (PullingAlgorithm::Umbrella): break; // this is equal to not using pulling
+                case (PullingAlgorithm::Constraint): ePullOld = PullingAlgorithm::Umbrella; break;
+                case (PullingAlgorithm::ConstantForce):
+                    ePullOld = PullingAlgorithm::Constraint;
+                    break;
+                case (PullingAlgorithm::FlatBottom):
+                    ePullOld = PullingAlgorithm::ConstantForce;
+                    break;
+                case (PullingAlgorithm::FlatBottomHigh):
+                    ePullOld = PullingAlgorithm::FlatBottom;
+                    break;
+                case (PullingAlgorithm::External):
+                    ePullOld = PullingAlgorithm::FlatBottomHigh;
+                    break;
+                case (PullingAlgorithm::Count): ePullOld = PullingAlgorithm::External; break;
+                default: GMX_RELEASE_ASSERT(false, "Unhandled old pull algorithm");
+            }
         }
         if (ir->bPull)
         {
             if (serializer->reading())
             {
-                snew(ir->pull, 1);
+                ir->pull = std::make_unique<pull_params_t>();
             }
-            do_pull(serializer, ir->pull, file_version, ePullOld);
+            do_pull(serializer, ir->pull.get(), file_version, ePullOld);
         }
     }
 
@@ -1483,9 +1521,12 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
         {
             if (serializer->reading())
             {
-                snew(ir->awhParams, 1);
+                ir->awhParams = std::make_unique<gmx::AwhParams>(serializer);
+            }
+            else
+            {
+                ir->awhParams->serialize(serializer);
             }
-            do_awh(serializer, ir->awhParams, file_version);
         }
     }
     else
@@ -1540,7 +1581,15 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     {
         ir->opts.nhchainlength = 1;
     }
-    serializer->doInt(&ir->opts.ngacc);
+    if (serializer->reading() && file_version >= tpxv_RemovedConstantAcceleration
+        && file_version < tpxv_ReaddedConstantAcceleration)
+    {
+        ir->opts.ngacc = 0;
+    }
+    else
+    {
+        serializer->doInt(&ir->opts.ngacc);
+    }
     serializer->doInt(&ir->opts.ngfrz);
     serializer->doInt(&ir->opts.ngener);
 
@@ -1554,7 +1603,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
         snew(ir->opts.anneal_temp, ir->opts.ngtc);
         snew(ir->opts.tau_t, ir->opts.ngtc);
         snew(ir->opts.nFreeze, ir->opts.ngfrz);
-        snew(ir->opts.acc, ir->opts.ngacc);
+        snew(ir->opts.acceleration, ir->opts.ngacc);
         snew(ir->opts.egp_flags, ir->opts.ngener * ir->opts.ngener);
     }
     if (ir->opts.ngtc > 0)
@@ -1569,12 +1618,23 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     }
     if (ir->opts.ngacc > 0)
     {
-        serializer->doRvecArray(ir->opts.acc, ir->opts.ngacc);
+        serializer->doRvecArray(ir->opts.acceleration, ir->opts.ngacc);
+    }
+    if (serializer->reading())
+    {
+        ir->useConstantAcceleration = false;
+        for (int g = 0; g < ir->opts.ngacc; g++)
+        {
+            if (norm2(ir->opts.acceleration[g]) != 0)
+            {
+                ir->useConstantAcceleration = true;
+            }
+        }
     }
     serializer->doIntArray(ir->opts.egp_flags, ir->opts.ngener * ir->opts.ngener);
 
     /* First read the lists with annealing and npoints for each group */
-    serializer->doIntArray(ir->opts.annealing, ir->opts.ngtc);
+    serializer->doEnumArrayAsInt(ir->opts.annealing, ir->opts.ngtc);
     serializer->doIntArray(ir->opts.anneal_npoints, ir->opts.ngtc);
     for (j = 0; j < (ir->opts.ngtc); j++)
     {
@@ -1590,7 +1650,7 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     /* Walls */
     {
         serializer->doInt(&ir->nwall);
-        serializer->doInt(&ir->wall_type);
+        serializer->doEnumAsInt(&ir->wall_type);
         serializer->doReal(&ir->wall_r_linpot);
         serializer->doInt(&ir->wall_atomtype[0]);
         serializer->doInt(&ir->wall_atomtype[1]);
@@ -1608,8 +1668,8 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
     /* Swap ions */
     if (file_version >= tpxv_ComputationalElectrophysiology)
     {
-        serializer->doInt(&ir->eSwapCoords);
-        if (ir->eSwapCoords != eswapNO)
+        serializer->doEnumAsInt(&ir->eSwapCoords);
+        if (ir->eSwapCoords != SwapType::No)
         {
             if (serializer->reading())
             {
@@ -1619,43 +1679,43 @@ static void do_inputrec(gmx::ISerializer* serializer, t_inputrec* ir, int file_v
         }
     }
 
-    /* QMMM stuff */
+    /* QMMM reading - despite defunct we require reading for backwards
+     * compability and correct serialization
+     */
     {
         serializer->doBool(&ir->bQMMM);
-        serializer->doInt(&ir->QMMMscheme);
-        serializer->doReal(&ir->scalefactor);
+        int qmmmScheme;
+        serializer->doInt(&qmmmScheme);
+        real unusedScalefactor;
+        serializer->doReal(&unusedScalefactor);
+
+        // this is still used in Mimic
         serializer->doInt(&ir->opts.ngQM);
-        if (serializer->reading())
-        {
-            snew(ir->opts.QMmethod, ir->opts.ngQM);
-            snew(ir->opts.QMbasis, ir->opts.ngQM);
-            snew(ir->opts.QMcharge, ir->opts.ngQM);
-            snew(ir->opts.QMmult, ir->opts.ngQM);
-            snew(ir->opts.bSH, ir->opts.ngQM);
-            snew(ir->opts.CASorbitals, ir->opts.ngQM);
-            snew(ir->opts.CASelectrons, ir->opts.ngQM);
-            snew(ir->opts.SAon, ir->opts.ngQM);
-            snew(ir->opts.SAoff, ir->opts.ngQM);
-            snew(ir->opts.SAsteps, ir->opts.ngQM);
-        }
         if (ir->opts.ngQM > 0 && ir->bQMMM)
         {
-            serializer->doIntArray(ir->opts.QMmethod, ir->opts.ngQM);
-            serializer->doIntArray(ir->opts.QMbasis, ir->opts.ngQM);
-            serializer->doIntArray(ir->opts.QMcharge, ir->opts.ngQM);
-            serializer->doIntArray(ir->opts.QMmult, ir->opts.ngQM);
-            serializer->doBoolArray(ir->opts.bSH, ir->opts.ngQM);
-            serializer->doIntArray(ir->opts.CASorbitals, ir->opts.ngQM);
-            serializer->doIntArray(ir->opts.CASelectrons, ir->opts.ngQM);
-            serializer->doRealArray(ir->opts.SAon, ir->opts.ngQM);
-            serializer->doRealArray(ir->opts.SAoff, ir->opts.ngQM);
-            serializer->doIntArray(ir->opts.SAsteps, ir->opts.ngQM);
             /* We leave in dummy i/o for removed parameters to avoid
-             * changing the tpr format for every QMMM change.
+             * changing the tpr format.
              */
-            std::vector<int> dummy(ir->opts.ngQM, 0);
-            serializer->doIntArray(dummy.data(), ir->opts.ngQM);
-            serializer->doIntArray(dummy.data(), ir->opts.ngQM);
+            std::vector<int> dummyIntVec(4 * ir->opts.ngQM, 0);
+            serializer->doIntArray(dummyIntVec.data(), dummyIntVec.size());
+            dummyIntVec.clear();
+
+            // std::vector<bool> has no data()
+            std::vector<char> dummyBoolVec(ir->opts.ngQM * sizeof(bool) / sizeof(char));
+            serializer->doBoolArray(reinterpret_cast<bool*>(dummyBoolVec.data()), dummyBoolVec.size());
+            dummyBoolVec.clear();
+
+            dummyIntVec.resize(2 * ir->opts.ngQM, 0);
+            serializer->doIntArray(dummyIntVec.data(), dummyIntVec.size());
+            dummyIntVec.clear();
+
+            std::vector<real> dummyRealVec(2 * ir->opts.ngQM, 0);
+            serializer->doRealArray(dummyRealVec.data(), dummyRealVec.size());
+            dummyRealVec.clear();
+
+            dummyIntVec.resize(3 * ir->opts.ngQM, 0);
+            serializer->doIntArray(dummyIntVec.data(), dummyIntVec.size());
+            dummyIntVec.clear();
         }
         /* end of QMMM stuff */
     }
@@ -1840,7 +1900,12 @@ static void do_iparams(gmx::ISerializer* serializer, t_functype ftype, t_iparams
             serializer->doReal(&iparams->thole.a);
             serializer->doReal(&iparams->thole.alpha1);
             serializer->doReal(&iparams->thole.alpha2);
-            serializer->doReal(&iparams->thole.rfac);
+            if (file_version < tpxv_RemoveTholeRfac)
+            {
+                real noRfac = 0;
+                serializer->doReal(&noRfac);
+            }
+
             break;
         case F_LJ:
             serializer->doReal(&iparams->lj.c6);
@@ -1931,9 +1996,7 @@ static void do_iparams(gmx::ISerializer* serializer, t_functype ftype, t_iparams
             break;
         case F_CBTDIHS: serializer->doRealArray(iparams->cbtdihs.cbtcA, NR_CBTDIHS); break;
         case F_RBDIHS:
-            serializer->doRealArray(iparams->rbdihs.rbcA, NR_RBDIHS);
-            serializer->doRealArray(iparams->rbdihs.rbcB, NR_RBDIHS);
-            break;
+            // Fall-through intended
         case F_FOURDIHS:
             /* Fourier dihedrals are internally represented
              * as Ryckaert-Bellemans since those are faster to compute.
@@ -1950,6 +2013,7 @@ static void do_iparams(gmx::ISerializer* serializer, t_functype ftype, t_iparams
             serializer->doReal(&iparams->settle.doh);
             serializer->doReal(&iparams->settle.dhh);
             break;
+        case F_VSITE1: break; // VSite1 has 0 parameters
         case F_VSITE2:
         case F_VSITE2FD: serializer->doReal(&iparams->vsite.a); break;
         case F_VSITE3:
@@ -1997,8 +2061,12 @@ static void do_iparams(gmx::ISerializer* serializer, t_functype ftype, t_iparams
             serializer->doInt(&iparams->cmap.cmapB);
             break;
         default:
-            gmx_fatal(FARGS, "unknown function type %d (%s) in %s line %d", ftype,
-                      interaction_function[ftype].name, __FILE__, __LINE__);
+            gmx_fatal(FARGS,
+                      "unknown function type %d (%s) in %s line %d",
+                      ftype,
+                      interaction_function[ftype].name,
+                      __FILE__,
+                      __LINE__);
     }
 }
 
@@ -2102,7 +2170,7 @@ static void do_ilists(gmx::ISerializer* serializer, InteractionLists* ilists, in
         else
         {
             do_ilist(serializer, &ilist);
-            if (file_version < 78 && j == F_SETTLE && ilist.size() > 0)
+            if (file_version < 78 && j == F_SETTLE && !ilist.empty())
             {
                 add_settle_atoms(&ilist);
             }
@@ -2194,7 +2262,7 @@ static void do_atom(gmx::ISerializer* serializer, t_atom* atom)
     serializer->doReal(&atom->qB);
     serializer->doUShort(&atom->type);
     serializer->doUShort(&atom->typeB);
-    serializer->doInt(&atom->ptype);
+    serializer->doEnumAsInt(&atom->ptype);
     serializer->doInt(&atom->resind);
     serializer->doInt(&atom->atomnumber);
     if (serializer->reading())
@@ -2493,17 +2561,13 @@ static void do_molblock(gmx::ISerializer* serializer, gmx_molblock_t* molb, int
 
 static void set_disres_npair(gmx_mtop_t* mtop)
 {
-    gmx_mtop_ilistloop_t iloop;
-    int                  nmol;
-
     gmx::ArrayRef<t_iparams> ip = mtop->ffparams.iparams;
 
-    iloop = gmx_mtop_ilistloop_init(mtop);
-    while (const InteractionLists* ilist = gmx_mtop_ilistloop_next(iloop, &nmol))
+    for (const auto ilist : IListRange(*mtop))
     {
-        const InteractionList& il = (*ilist)[F_DISRES];
+        const InteractionList& il = ilist.list()[F_DISRES];
 
-        if (il.size() > 0)
+        if (!il.empty())
         {
             gmx::ArrayRef<const int> a     = il.iatoms;
             int                      npair = 0;
@@ -2585,6 +2649,18 @@ static void do_mtop(gmx::ISerializer* serializer, gmx_mtop_t* mtop, int file_ver
 
     mtop->haveMoleculeIndices = true;
 
+    if (file_version >= tpxv_StoreNonBondedInteractionExclusionGroup)
+    {
+        std::int64_t intermolecularExclusionGroupSize = gmx::ssize(mtop->intermolecularExclusionGroup);
+        serializer->doInt64(&intermolecularExclusionGroupSize);
+        GMX_RELEASE_ASSERT(intermolecularExclusionGroupSize >= 0,
+                           "Number of atoms with excluded intermolecular non-bonded interactions "
+                           "is negative.");
+        mtop->intermolecularExclusionGroup.resize(intermolecularExclusionGroupSize); // no effect when writing
+        serializer->doIntArray(mtop->intermolecularExclusionGroup.data(),
+                               mtop->intermolecularExclusionGroup.size());
+    }
+
     if (serializer->reading())
     {
         close_symtab(&(mtop->symtab));
@@ -2648,10 +2724,16 @@ static void do_tpxheader(gmx::FileIOXdrSerializer* serializer,
             gmx_fatal(FARGS,
                       "Unknown precision in file %s: real is %d bytes "
                       "instead of %zu or %zu",
-                      filename, precision, sizeof(float), sizeof(double));
+                      filename,
+                      precision,
+                      sizeof(float),
+                      sizeof(double));
         }
         gmx_fio_setprecision(fio, tpx->isDouble);
-        fprintf(stderr, "Reading file %s, %s (%s precision)\n", filename, buf.c_str(),
+        fprintf(stderr,
+                "Reading file %s, %s (%s precision)\n",
+                filename,
+                buf.c_str(),
                 tpx->isDouble ? "double" : "single");
     }
     else
@@ -2660,7 +2742,7 @@ static void do_tpxheader(gmx::FileIOXdrSerializer* serializer,
         serializer->doString(&buf);
         gmx_fio_setprecision(fio, tpx->isDouble);
         serializer->doInt(&precision);
-        fileTag = gmx::formatString("%s", tpx_tag);
+        fileTag = tpx_tag;
     }
 
     /* Check versions! */
@@ -2692,7 +2774,7 @@ static void do_tpxheader(gmx::FileIOXdrSerializer* serializer,
 
         if (fileTag != tpx_tag)
         {
-            fprintf(stderr, "Note: file tpx tag '%s', software tpx tag '%s'\n", fileTag.c_str(), tpx_tag);
+            fprintf(stderr, "Note: file tpx tag '%s', software tpx tag '%s'\n", fileTag.c_str(), tpx_tag.c_str());
 
             /* We only support reading tpx files with the same tag as the code
              * or tpx files with the release tag and with lower version number.
@@ -2702,7 +2784,11 @@ static void do_tpxheader(gmx::FileIOXdrSerializer* serializer,
                 gmx_fatal(FARGS,
                           "tpx tag/version mismatch: reading tpx file (%s) version %d, tag '%s' "
                           "with program for tpx version %d, tag '%s'",
-                          filename, tpx->fileVersion, fileTag.c_str(), tpx_version, tpx_tag);
+                          filename,
+                          tpx->fileVersion,
+                          fileTag.c_str(),
+                          tpx_version,
+                          tpx_tag.c_str());
             }
         }
     }
@@ -2711,8 +2797,11 @@ static void do_tpxheader(gmx::FileIOXdrSerializer* serializer,
         || ((tpx->fileVersion > tpx_version) && !TopOnlyOK) || (tpx->fileGeneration > tpx_generation)
         || tpx_version == 80) /*80 was used by both 5.0-dev and 4.6-dev*/
     {
-        gmx_fatal(FARGS, "reading tpx file (%s) version %d with version %d program", filename,
-                  tpx->fileVersion, tpx_version);
+        gmx_fatal(FARGS,
+                  "reading tpx file (%s) version %d with version %d program",
+                  filename,
+                  tpx->fileVersion,
+                  tpx_version);
     }
 
     serializer->doInt(&tpx->natoms);
@@ -2832,7 +2921,7 @@ static void do_tpx_mtop(gmx::ISerializer* serializer, TpxFileHeader* tpx, gmx_mt
         {
             do_mtop(serializer, mtop, tpx->fileVersion);
             set_disres_npair(mtop);
-            gmx_mtop_finalize(mtop);
+            mtop->finalize();
         }
         else
         {
@@ -2878,11 +2967,11 @@ static void do_tpx_state_second(gmx::ISerializer* serializer, TpxFileHeader* tpx
             // of the tpx file.
             if (tpx->bX)
             {
-                state->flags |= (1 << estX);
+                state->flags |= enumValueToBitMask(StateEntry::X);
             }
             if (tpx->bV)
             {
-                state->flags |= (1 << estV);
+                state->flags |= enumValueToBitMask(StateEntry::V);
             }
             state_change_natoms(state, tpx->natoms);
         }
@@ -2898,7 +2987,7 @@ static void do_tpx_state_second(gmx::ISerializer* serializer, TpxFileHeader* tpx
     {
         if (serializer->reading())
         {
-            state->flags |= (1 << estX);
+            state->flags |= enumValueToBitMask(StateEntry::X);
         }
         serializer->doRvecArray(x, tpx->natoms);
     }
@@ -2908,7 +2997,7 @@ static void do_tpx_state_second(gmx::ISerializer* serializer, TpxFileHeader* tpx
     {
         if (serializer->reading())
         {
-            state->flags |= (1 << estV);
+            state->flags |= enumValueToBitMask(StateEntry::V);
         }
         if (!v)
         {
@@ -2938,9 +3027,9 @@ static void do_tpx_state_second(gmx::ISerializer* serializer, TpxFileHeader* tpx
  * \param[in] tpx The file header data.
  * \param[in,out] ir Datastructure with simulation parameters.
  */
-static int do_tpx_ir(gmx::ISerializer* serializer, TpxFileHeader* tpx, t_inputrec* ir)
+static PbcType do_tpx_ir(gmx::ISerializer* serializer, TpxFileHeader* tpx, t_inputrec* ir)
 {
-    int      ePBC;
+    PbcType  pbcType;
     gmx_bool bPeriodicMols;
 
     /* Starting with tpx version 26, we have the inputrec
@@ -2950,7 +3039,7 @@ static int do_tpx_ir(gmx::ISerializer* serializer, TpxFileHeader* tpx, t_inputre
      *
      *
      */
-    ePBC          = -1;
+    pbcType       = PbcType::Unset;
     bPeriodicMols = FALSE;
 
     do_test(serializer, tpx->bIr, ir);
@@ -2961,10 +3050,10 @@ static int do_tpx_ir(gmx::ISerializer* serializer, TpxFileHeader* tpx, t_inputre
             /* Removed the pbc info from do_inputrec, since we always want it */
             if (!serializer->reading())
             {
-                ePBC          = ir->ePBC;
+                pbcType       = ir->pbcType;
                 bPeriodicMols = ir->bPeriodicMols;
             }
-            serializer->doInt(&ePBC);
+            serializer->doInt(reinterpret_cast<int*>(&pbcType));
             serializer->doBool(&bPeriodicMols);
         }
         if (tpx->fileGeneration <= tpx_generation && ir)
@@ -2972,18 +3061,18 @@ static int do_tpx_ir(gmx::ISerializer* serializer, TpxFileHeader* tpx, t_inputre
             do_inputrec(serializer, ir, tpx->fileVersion);
             if (tpx->fileVersion < 53)
             {
-                ePBC          = ir->ePBC;
+                pbcType       = ir->pbcType;
                 bPeriodicMols = ir->bPeriodicMols;
             }
         }
         if (serializer->reading() && ir && tpx->fileVersion >= 53)
         {
             /* We need to do this after do_inputrec, since that initializes ir */
-            ir->ePBC          = ePBC;
+            ir->pbcType       = pbcType;
             ir->bPeriodicMols = bPeriodicMols;
         }
     }
-    return ePBC;
+    return pbcType;
 }
 
 /*! \brief
@@ -3016,14 +3105,9 @@ static void do_tpx_finalize(TpxFileHeader* tpx, t_inputrec* ir, t_state* state,
         {
             if (tpx->fileVersion < 57)
             {
-                if (mtop->moltype[0].ilist[F_DISRES].size() > 0)
-                {
-                    ir->eDisre = edrSimple;
-                }
-                else
-                {
-                    ir->eDisre = edrNone;
-                }
+                ir->eDisre = !mtop->moltype[0].ilist[F_DISRES].empty()
+                                     ? DistanceRestraintRefinement::Simple
+                                     : DistanceRestraintRefinement::None;
             }
         }
     }
@@ -3049,13 +3133,13 @@ static void do_tpx_finalize(TpxFileHeader* tpx, t_inputrec* ir, t_state* state,
  * \param[in,out] v Individual velocities for processing, deprecated.
  * \param[in,out] mtop Global topology.
  */
-static int do_tpx_body(gmx::ISerializer* serializer,
-                       TpxFileHeader*    tpx,
-                       t_inputrec*       ir,
-                       t_state*          state,
-                       rvec*             x,
-                       rvec*             v,
-                       gmx_mtop_t*       mtop)
+static PbcType do_tpx_body(gmx::ISerializer* serializer,
+                           TpxFileHeader*    tpx,
+                           t_inputrec*       ir,
+                           t_state*          state,
+                           rvec*             x,
+                           rvec*             v,
+                           gmx_mtop_t*       mtop)
 {
     if (state)
     {
@@ -3066,12 +3150,12 @@ static int do_tpx_body(gmx::ISerializer* serializer,
     {
         do_tpx_state_second(serializer, tpx, state, x, v);
     }
-    int ePBC = do_tpx_ir(serializer, tpx, ir);
+    PbcType pbcType = do_tpx_ir(serializer, tpx, ir);
     if (serializer->reading())
     {
         do_tpx_finalize(tpx, ir, state, mtop);
     }
-    return ePBC;
+    return pbcType;
 }
 
 /*! \brief
@@ -3082,7 +3166,7 @@ static int do_tpx_body(gmx::ISerializer* serializer,
  * \param[in,out] ir Datastructures with simulation parameters.
  * \param[in,out] mtop Global topology.
  */
-static int do_tpx_body(gmx::ISerializer* serializer, TpxFileHeader* tpx, t_inputrec* ir, gmx_mtop_t* mtop)
+static PbcType do_tpx_body(gmx::ISerializer* serializer, TpxFileHeader* tpx, t_inputrec* ir, gmx_mtop_t* mtop)
 {
     return do_tpx_body(serializer, tpx, ir, nullptr, nullptr, nullptr, mtop);
 }
@@ -3114,11 +3198,11 @@ static TpxFileHeader populateTpxHeader(const t_state& state, const t_inputrec* i
     header.natoms         = state.natoms;
     header.ngtc           = state.ngtc;
     header.fep_state      = state.fep_state;
-    header.lambda         = state.lambda[efptFEP];
+    header.lambda         = state.lambda[FreeEnergyPerturbationCouplingType::Fep];
     header.bIr            = ir != nullptr;
     header.bTop           = mtop != nullptr;
-    header.bX             = (state.flags & (1 << estX)) != 0;
-    header.bV             = (state.flags & (1 << estV)) != 0;
+    header.bX             = (state.flags & enumValueToBitMask(StateEntry::X)) != 0;
+    header.bV             = (state.flags & enumValueToBitMask(StateEntry::V)) != 0;
     header.bF             = false;
     header.bBox           = true;
     header.fileVersion    = tpx_version;
@@ -3129,7 +3213,7 @@ static TpxFileHeader populateTpxHeader(const t_state& state, const t_inputrec* i
 }
 
 /*! \brief
- * Process the body of a TPR file as char buffer.
+ * Process the body of a TPR file as an opaque data buffer.
  *
  * Reads/writes the information in \p buffer from/to the \p serializer
  * provided to the function. Does not interact with the actual
@@ -3143,7 +3227,7 @@ static TpxFileHeader populateTpxHeader(const t_state& state, const t_inputrec* i
  */
 static void doTpxBodyBuffer(gmx::ISerializer* serializer, gmx::ArrayRef<char> buffer)
 {
-    serializer->doCharArray(buffer.data(), buffer.size());
+    serializer->doOpaque(buffer.data(), buffer.size());
 }
 
 /*! \brief
@@ -3187,19 +3271,24 @@ static PartialDeserializedTprFile readTpxBody(TpxFileHeader*    tpx,
         partialDeserializedTpr.header = *tpx;
         doTpxBodyBuffer(serializer, partialDeserializedTpr.body);
 
-        partialDeserializedTpr.ePBC =
+        partialDeserializedTpr.pbcType =
                 completeTprDeserialization(&partialDeserializedTpr, ir, state, x, v, mtop);
     }
     else
     {
-        partialDeserializedTpr.ePBC = do_tpx_body(serializer, tpx, ir, state, x, v, mtop);
+        partialDeserializedTpr.pbcType = do_tpx_body(serializer, tpx, ir, state, x, v, mtop);
     }
     // Update header to system info for communication to nodes.
     // As we only need to communicate the inputrec and mtop to other nodes,
     // we prepare a new char buffer with the information we have already read
     // in on master.
     partialDeserializedTpr.header = populateTpxHeader(*state, ir, mtop);
-    gmx::InMemorySerializer tprBodySerializer;
+    // Long-term we should move to use little endian in files to avoid extra byte swapping,
+    // but since we just used the default XDR format (which is big endian) for the TPR
+    // header it would cause third-party libraries reading our raw data to tear their hair
+    // if we swap the endian in the middle of the file, so we stick to big endian in the
+    // TPR file for now - and thus we ask the serializer to swap if this host is little endian.
+    gmx::InMemorySerializer tprBodySerializer(gmx::EndianSwapBehavior::SwapIfHostIsLittleEndian);
     do_tpx_body(&tprBodySerializer, &partialDeserializedTpr.header, ir, mtop);
     partialDeserializedTpr.body = tprBodySerializer.finishAndGetBuffer();
 
@@ -3225,7 +3314,7 @@ TpxFileHeader readTpxHeader(const char* fileName, bool canReadTopologyOnly)
     return tpx;
 }
 
-void write_tpx_state(const char* fn, const t_inputrec* ir, const t_state* state, const gmx_mtop_t* mtop)
+void write_tpx_state(const char* fn, const t_inputrec* ir, const t_state* state, const gmx_mtop_t& mtop)
 {
     /* To write a state, we first need to write the state information to a buffer before
      * we append the raw bytes to the file. For this, the header information needs to be
@@ -3235,12 +3324,21 @@ void write_tpx_state(const char* fn, const t_inputrec* ir, const t_state* state,
 
     t_fileio* fio;
 
-    TpxFileHeader tpx = populateTpxHeader(*state, ir, mtop);
-
-    gmx::InMemorySerializer tprBodySerializer;
-
-    do_tpx_body(&tprBodySerializer, &tpx, const_cast<t_inputrec*>(ir), const_cast<t_state*>(state),
-                nullptr, nullptr, const_cast<gmx_mtop_t*>(mtop));
+    TpxFileHeader tpx = populateTpxHeader(*state, ir, &mtop);
+    // Long-term we should move to use little endian in files to avoid extra byte swapping,
+    // but since we just used the default XDR format (which is big endian) for the TPR
+    // header it would cause third-party libraries reading our raw data to tear their hair
+    // if we swap the endian in the middle of the file, so we stick to big endian in the
+    // TPR file for now - and thus we ask the serializer to swap if this host is little endian.
+    gmx::InMemorySerializer tprBodySerializer(gmx::EndianSwapBehavior::SwapIfHostIsLittleEndian);
+
+    do_tpx_body(&tprBodySerializer,
+                &tpx,
+                const_cast<t_inputrec*>(ir),
+                const_cast<t_state*>(state),
+                nullptr,
+                nullptr,
+                const_cast<gmx_mtop_t*>(&mtop));
 
     std::vector<char> tprBody = tprBodySerializer.finishAndGetBuffer();
     tpx.sizeOfTprBody         = tprBody.size();
@@ -3253,21 +3351,27 @@ void write_tpx_state(const char* fn, const t_inputrec* ir, const t_state* state,
     close_tpx(fio);
 }
 
-int completeTprDeserialization(PartialDeserializedTprFile* partialDeserializedTpr,
-                               t_inputrec*                 ir,
-                               t_state*                    state,
-                               rvec*                       x,
-                               rvec*                       v,
-                               gmx_mtop_t*                 mtop)
+PbcType completeTprDeserialization(PartialDeserializedTprFile* partialDeserializedTpr,
+                                   t_inputrec*                 ir,
+                                   t_state*                    state,
+                                   rvec*                       x,
+                                   rvec*                       v,
+                                   gmx_mtop_t*                 mtop)
 {
+    // Long-term we should move to use little endian in files to avoid extra byte swapping,
+    // but since we just used the default XDR format (which is big endian) for the TPR
+    // header it would cause third-party libraries reading our raw data to tear their hair
+    // if we swap the endian in the middle of the file, so we stick to big endian in the
+    // TPR file for now - and thus we ask the serializer to swap if this host is little endian.
     gmx::InMemoryDeserializer tprBodyDeserializer(partialDeserializedTpr->body,
-                                                  partialDeserializedTpr->header.isDouble);
+                                                  partialDeserializedTpr->header.isDouble,
+                                                  gmx::EndianSwapBehavior::SwapIfHostIsLittleEndian);
     return do_tpx_body(&tprBodyDeserializer, &partialDeserializedTpr->header, ir, state, x, v, mtop);
 }
 
-int completeTprDeserialization(PartialDeserializedTprFile* partialDeserializedTpr,
-                               t_inputrec*                 ir,
-                               gmx_mtop_t*                 mtop)
+PbcType completeTprDeserialization(PartialDeserializedTprFile* partialDeserializedTpr,
+                                   t_inputrec*                 ir,
+                                   gmx_mtop_t*                 mtop)
 {
     return completeTprDeserialization(partialDeserializedTpr, ir, nullptr, nullptr, nullptr, mtop);
 }
@@ -3285,7 +3389,7 @@ PartialDeserializedTprFile read_tpx_state(const char* fn, t_inputrec* ir, t_stat
     return partialDeserializedTpr;
 }
 
-int read_tpx(const char* fn, t_inputrec* ir, matrix box, int* natoms, rvec* x, rvec* v, gmx_mtop_t* mtop)
+PbcType read_tpx(const char* fn, t_inputrec* ir, matrix box, int* natoms, rvec* x, rvec* v, gmx_mtop_t* mtop)
 {
     t_fileio* fio;
     t_state   state;
@@ -3305,19 +3409,19 @@ int read_tpx(const char* fn, t_inputrec* ir, matrix box, int* natoms, rvec* x, r
     {
         copy_mat(state.box, box);
     }
-    return partialDeserializedTpr.ePBC;
+    return partialDeserializedTpr.pbcType;
 }
 
-int read_tpx_top(const char* fn, t_inputrec* ir, matrix box, int* natoms, rvec* x, rvec* v, t_topology* top)
+PbcType read_tpx_top(const char* fn, t_inputrec* ir, matrix box, int* natoms, rvec* x, rvec* v, t_topology* top)
 {
     gmx_mtop_t mtop;
-    int        ePBC;
+    PbcType    pbcType;
 
-    ePBC = read_tpx(fn, ir, box, natoms, x, v, &mtop);
+    pbcType = read_tpx(fn, ir, box, natoms, x, v, &mtop);
 
     *top = gmx_mtop_t_to_t_topology(&mtop, true);
 
-    return ePBC;
+    return pbcType;
 }
 
 gmx_bool fn2bTPX(const char* file)