src/gromacs/utility/physicalnodecommunicator.cpp

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  35 /*! \internal \file
  36  * \brief
  37  * Defines functionality for communicators across physical nodes.
  38  *
  39  * \ingroup module_utility
  40  */
  41 #include "gmxpre.h"
  42
  43 #include "physicalnodecommunicator.h"
  44
  45 #include "config.h"
  46
  47 #include "gromacs/utility/basedefinitions.h"
  48 #include "gromacs/utility/gmxmpi.h"
  49
  50 namespace gmx
  51 {
  52
  53 void
  54 MPI_Comm_free_wrapper(MPI_Comm *comm)
  55 {
  56 #if GMX_MPI
  57     // With thread-MPI *comm is shared between ranks which causes issues with
  58     // freeing. But all thread-mpi data is anyhow freed in tMPI_Finalize()
  59     // and in practice *comm is always MPI_COMM_WORLD with thread-MPI.
  60     // Only the thread-affinity test code uses *comm != MPI_COMM_WORLD.
  61     if (!GMX_THREAD_MPI)
  62     {
  63         MPI_Comm_free(comm);
  64     }
  65 #else
  66     GMX_UNUSED_VALUE(comm);
  67 #endif
  68 }
  69
  70 PhysicalNodeCommunicator::PhysicalNodeCommunicator(MPI_Comm world, int physicalNodeId)
  71 {
  72 #if GMX_MPI
  73     int isInitialized;
  74     MPI_Initialized(&isInitialized);
  75     if (isInitialized)
  76     {
  77         int sizeOfWorld;
  78         MPI_Comm_size(world, &sizeOfWorld);
  79         if (sizeOfWorld > 1)
  80         {
  81             int rankWithinWorld;
  82             MPI_Comm_rank(world, &rankWithinWorld);
  83             MPI_Comm_split(world, physicalNodeId, rankWithinWorld, &comm_);
  84             auto ptr = MPI_Comm_ptr(&comm_);
  85             commGuard_.swap(ptr);
  86             MPI_Comm_size(comm_, &size_);
  87             MPI_Comm_rank(comm_, &rank_);
  88         }
  89         else
  90         {
  91             // Handle this trivial case separately, because thread-MPI
  92             // doesn't have a valid communicator when there is only
  93             // one rank.
  94             comm_ = world;
  95             size_ = 1;
  96             rank_ = 0;
  97         }
  98     }
  99     else
 100     {
 101         comm_ = MPI_COMM_NULL;
 102         size_ = 1;
 103         rank_ = 0;
 104     }
 105 #else
 106     // Trivial case when there is no MPI support or not initialized
 107     GMX_UNUSED_VALUE(world);
 108     GMX_UNUSED_VALUE(physicalNodeId);
 109     comm_ = nullptr;
 110     size_ = 1;
 111     rank_ = 0;
 112 #endif
 113 }
 114
 115 void PhysicalNodeCommunicator::barrier() const
 116 {
 117 #if GMX_MPI
 118     if (size_ > 1)
 119     {
 120         MPI_Barrier(comm_);
 121     }
 122 #else
 123     // Nothing to do
 124 #endif
 125 }
 126
 127 }  // namespace gmx