Change the behavior of the GPU update UI

1. By default, update will now run on the CPU
2. The "-update cpu" will override the GMX_FORCE_UPDATE_DEFAULT_GPU
   environment variable.

Change-Id: I08efb6a594fb062fe145baa7cc00ba5c8ec63374

diff --git a/docs/release-notes/2020/major/performance.rst b/docs/release-notes/2020/major/performance.rst
index a9ab8d75e2410a89f324fb39118121c7ad233db4..784d4b83a1dcef7b335f1fe68b7f3980dcffd348 100644 (file)
--- a/docs/release-notes/2020/major/performance.rst
+++ b/docs/release-notes/2020/major/performance.rst
@@ -36,6 +36,8 @@ For standard simulations (see the user guide for more details),
 update and constraints can be offloaded to a GPU with CUDA. Thus all compute
 intensive parts of a simulation can be offloaded, which provides
 better performance when using a fast GPU combined with a slow CPU.
+By default, update will run on the CPU, to use GPU in single rank simulations,
+one can use new '-update gpu' command line option.
 For use with domain decomposition, please see below.
 
 GPU Direct Communications

diff --git a/src/gromacs/mdrun/runner.cpp b/src/gromacs/mdrun/runner.cpp
index 477ae85b44ce8e03bbe4d2e0f4c193c0510eb924..f5b9cb1b7ab66d47a762e7f311f315a601023ae5 100644 (file)
--- a/src/gromacs/mdrun/runner.cpp
+++ b/src/gromacs/mdrun/runner.cpp
@@ -176,8 +176,8 @@ struct DevelopmentFeatureFlags
     //! True if the Buffer ops development feature is enabled
     // TODO: when the trigger of the buffer ops offload is fully automated this should go away
     bool enableGpuBufferOps = false;
-    //! If true, forces 'mdrun -update auto' default to 'gpu' when running with DD
-    bool forceGpuUpdateDefaultWithDD = false;
+    //! If true, forces 'mdrun -update auto' default to 'gpu'
+    bool forceGpuUpdateDefault = false;
     //! True if the GPU halo exchange development feature is enabled
     bool enableGpuHaloExchange = false;
     //! True if the PME PP direct communication GPU development feature is enabled
@@ -212,7 +212,7 @@ static DevelopmentFeatureFlags manageDevelopmentFeatures(const gmx::MDLogger& md
 #pragma GCC diagnostic ignored "-Wunused-result"
     devFlags.enableGpuBufferOps = (getenv("GMX_USE_GPU_BUFFER_OPS") != nullptr)
                                   && (GMX_GPU == GMX_GPU_CUDA) && useGpuForNonbonded;
-    devFlags.forceGpuUpdateDefaultWithDD = (getenv("GMX_FORCE_UPDATE_DEFAULT_GPU") != nullptr);
+    devFlags.forceGpuUpdateDefault = (getenv("GMX_FORCE_UPDATE_DEFAULT_GPU") != nullptr);
     devFlags.enableGpuHaloExchange =
             (getenv("GMX_GPU_DD_COMMS") != nullptr && GMX_THREAD_MPI && (GMX_GPU == GMX_GPU_CUDA));
     devFlags.enableGpuPmePPComm =
@@ -228,7 +228,7 @@ static DevelopmentFeatureFlags manageDevelopmentFeatures(const gmx::MDLogger& md
                         "GMX_USE_GPU_BUFFER_OPS environment variable.");
     }
 
-    if (devFlags.forceGpuUpdateDefaultWithDD)
+    if (devFlags.forceGpuUpdateDefault)
     {
         GMX_LOG(mdlog.warning)
                 .asParagraph()
@@ -1191,10 +1191,9 @@ int Mdrunner::mdrunner()
         const bool useUpdateGroups = cr->dd ? ddUsesUpdateGroups(*cr->dd) : false;
 
         useGpuForUpdate = decideWhetherToUseGpuForUpdate(
-                devFlags.forceGpuUpdateDefaultWithDD, useDomainDecomposition, useUpdateGroups,
-                useGpuForPme, useGpuForNonbonded, updateTarget, gpusWereDetected, *inputrec, mtop,
-                doEssentialDynamics, gmx_mtop_ftype_count(mtop, F_ORIRES) > 0,
-                replExParams.exchangeInterval > 0, doRerun);
+                devFlags.forceGpuUpdateDefault, useDomainDecomposition, useUpdateGroups, useGpuForPme,
+                useGpuForNonbonded, updateTarget, gpusWereDetected, *inputrec, mtop, doEssentialDynamics,
+                gmx_mtop_ftype_count(mtop, F_ORIRES) > 0, replExParams.exchangeInterval > 0, doRerun);
     }
     GMX_CATCH_ALL_AND_EXIT_WITH_FATAL_ERROR
 

diff --git a/src/gromacs/taskassignment/decidegpuusage.cpp b/src/gromacs/taskassignment/decidegpuusage.cpp
index adda067bfadb5aa61aafaf44df584209f96c5674..9b069fd890a44c139a700fe8bc9a00001855848a 100644 (file)
--- a/src/gromacs/taskassignment/decidegpuusage.cpp
+++ b/src/gromacs/taskassignment/decidegpuusage.cpp
@@ -489,7 +489,7 @@ bool decideWhetherToUseGpusForBonded(const bool       useGpuForNonbonded,
     return gpusWereDetected && usingOurCpuForPmeOrEwald;
 }
 
-bool decideWhetherToUseGpuForUpdate(const bool        forceGpuUpdateDefaultWithDD,
+bool decideWhetherToUseGpuForUpdate(const bool        forceGpuUpdateDefault,
                                     const bool        isDomainDecomposition,
                                     const bool        useUpdateGroups,
                                     const bool        useGpuForPme,
@@ -504,7 +504,8 @@ bool decideWhetherToUseGpuForUpdate(const bool        forceGpuUpdateDefaultWithD
                                     const bool        doRerun)
 {
 
-    if (updateTarget == TaskTarget::Cpu)
+    // '-update cpu' overrides the environment variable, '-update auto' does not
+    if (updateTarget == TaskTarget::Cpu || (updateTarget == TaskTarget::Auto && !forceGpuUpdateDefault))
     {
         return false;
     }
@@ -515,7 +516,7 @@ bool decideWhetherToUseGpuForUpdate(const bool        forceGpuUpdateDefaultWithD
 
     if (isDomainDecomposition)
     {
-        if (!forceGpuUpdateDefaultWithDD)
+        if (!forceGpuUpdateDefault)
         {
             errorMessage += "Domain decomposition is not supported.\n ";
         }
@@ -627,10 +628,12 @@ bool decideWhetherToUseGpuForUpdate(const bool        forceGpuUpdateDefaultWithD
 
     if (isDomainDecomposition)
     {
-        return forceGpuUpdateDefaultWithDD;
+        return forceGpuUpdateDefault;
+    }
+    else
+    {
+        return (updateTarget == TaskTarget::Gpu || forceGpuUpdateDefault);
     }
-
-    return true;
 }
 
 } // namespace gmx

diff --git a/src/gromacs/taskassignment/decidegpuusage.h b/src/gromacs/taskassignment/decidegpuusage.h
index a1929f1c16fe335f6f341786ad61a3361b1a703f..45ba2d333f43312593fdec38641d882d5532319e 100644 (file)
--- a/src/gromacs/taskassignment/decidegpuusage.h
+++ b/src/gromacs/taskassignment/decidegpuusage.h
@@ -232,7 +232,7 @@ bool decideWhetherToUseGpusForBonded(bool       useGpuForNonbonded,
 
 /*! \brief Decide whether to use GPU for update.
  *
- * \param[in]  forceGpuUpdateDefaultWithDD  If update should run on GPU with DD by default.
+ * \param[in]  forceGpuUpdateDefault        If update should run on GPU by default.
  * \param[in]  isDomainDecomposition        Whether there more than one domain.
  * \param[in]  useUpdateGroups              If the constraints can be split across domains.
  * \param[in]  useGpuForPme                 Whether GPUs will be used for PME interactions.
@@ -250,7 +250,7 @@ bool decideWhetherToUseGpusForBonded(bool       useGpuForNonbonded,
  * \throws     std::bad_alloc            If out of memory
  *             InconsistentInputError    If the user requirements are inconsistent.
  */
-bool decideWhetherToUseGpuForUpdate(bool              forceGpuUpdateDefaultWithDD,
+bool decideWhetherToUseGpuForUpdate(bool              forceGpuUpdateDefault,
                                     bool              isDomainDecomposition,
                                     bool              useUpdateGroups,
                                     bool              useGpuForPme,