comm_mpi.cpp

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <mpi.h>

#include <quda_internal.h>
#include <comm_quda.h>


#define MPI_CHECK(mpi_call) do {                    \
  int status = mpi_call;                            \
  if (status != MPI_SUCCESS) {                      \
    char err_string[128];                           \
    int err_len;                                    \
    MPI_Error_string(status, err_string, &err_len); \
    err_string[127] = '\0';                         \
    errorQuda("(MPI) %s", err_string);              \
  }                                                 \
} while (0)


struct MsgHandle_s {
  MPI_Request request;
};


static int rank = -1;
static int size = -1;
static int gpuid = -1;


void comm_init(int ndim, const int *dims, QudaCommsMap rank_from_coords, void *map_data)
{
  int initialized;
  MPI_CHECK( MPI_Initialized(&initialized) );

  if (!initialized) {
    errorQuda("MPI has not been initialized");
  }

  MPI_CHECK( MPI_Comm_rank(MPI_COMM_WORLD, &rank) );
  MPI_CHECK( MPI_Comm_size(MPI_COMM_WORLD, &size) );

  int grid_size = 1;
  for (int i = 0; i < ndim; i++) {
    grid_size *= dims[i];
  }
  if (grid_size != size) {
    errorQuda("Communication grid size declared via initCommsGridQuda() does not match"
              " total number of MPI ranks (%d != %d)", grid_size, size);
  }

  Topology *topo = comm_create_topology(ndim, dims, rank_from_coords, map_data);
  comm_set_default_topology(topo);

  // determine which GPU this MPI rank will use

  char *hostname = comm_hostname();
  char *hostname_recv_buf = (char *)safe_malloc(128*size);
  
  MPI_CHECK( MPI_Allgather(hostname, 128, MPI_CHAR, hostname_recv_buf, 128, MPI_CHAR, MPI_COMM_WORLD) );

  gpuid = 0;
  for (int i = 0; i < rank; i++) {
    if (!strncmp(hostname, &hostname_recv_buf[128*i], 128)) {
      gpuid++;
    }
  }
  host_free(hostname_recv_buf);

  int device_count;
  cudaGetDeviceCount(&device_count);
  if (device_count == 0) {
    errorQuda("No CUDA devices found");
  }
  if (gpuid >= device_count) {
    errorQuda("Too few GPUs available on %s", hostname);
  }
}


int comm_rank(void)
{
  return rank;
}


int comm_size(void)
{
  return size;
}


int comm_gpuid(void)
{
  return gpuid;
}


MsgHandle *comm_declare_send_displaced(void *buffer, const int displacement[], size_t nbytes)
{
  Topology *topo = comm_default_topology();

  int rank = comm_rank_displaced(topo, displacement);
  int tag = comm_rank();
  MsgHandle *mh = (MsgHandle *)safe_malloc(sizeof(MsgHandle));
  MPI_CHECK( MPI_Send_init(buffer, nbytes, MPI_BYTE, rank, tag, MPI_COMM_WORLD, &(mh->request)) );

  return mh;
}


MsgHandle *comm_declare_receive_displaced(void *buffer, const int displacement[], size_t nbytes)
{
  Topology *topo = comm_default_topology();

  int rank = comm_rank_displaced(topo, displacement);
  int tag = rank;
  MsgHandle *mh = (MsgHandle *)safe_malloc(sizeof(MsgHandle));
  MPI_CHECK( MPI_Recv_init(buffer, nbytes, MPI_BYTE, rank, tag, MPI_COMM_WORLD, &(mh->request)) );

  return mh;
}


void comm_free(MsgHandle *mh)
{
  host_free(mh);
}


void comm_start(MsgHandle *mh)
{
  MPI_CHECK( MPI_Start(&(mh->request)) );
}


void comm_wait(MsgHandle *mh)
{
  MPI_CHECK( MPI_Wait(&(mh->request), MPI_STATUS_IGNORE) );
}


int comm_query(MsgHandle *mh) 
{
  int query;
  MPI_CHECK( MPI_Test(&(mh->request), &query, MPI_STATUS_IGNORE) );

  return query;
}


void comm_allreduce(double* data)
{
  double recvbuf;
  MPI_CHECK( MPI_Allreduce(data, &recvbuf, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD) );
  *data = recvbuf;
} 


void comm_allreduce_max(double* data)
{
  double recvbuf;
  MPI_CHECK( MPI_Allreduce(data, &recvbuf, 1, MPI_DOUBLE, MPI_MAX, MPI_COMM_WORLD) );
  *data = recvbuf;
} 


void comm_allreduce_array(double* data, size_t size)
{
  double recvbuf[size];
  MPI_CHECK( MPI_Allreduce(data, &recvbuf, size, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD) );
  memcpy(data, recvbuf, sizeof(recvbuf));
}


void comm_allreduce_int(int* data)
{
  int recvbuf;
  MPI_CHECK( MPI_Allreduce(data, &recvbuf, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD) );
  *data = recvbuf;
}


void comm_broadcast(void *data, size_t nbytes)
{
  MPI_CHECK( MPI_Bcast(data, (int)nbytes, MPI_BYTE, 0, MPI_COMM_WORLD) );
}


void comm_barrier(void)
{
  MPI_CHECK( MPI_Barrier(MPI_COMM_WORLD) );
}


void comm_abort(int status)
{
  MPI_CHECK( MPI_Finalize() );
  exit(status);
}