waitall2.c

MPICH是MPI的重要研究,提供了一系列的接口函数,为并行计算的实现提供了编程环境.

/*
  Test of waitall.  This makes sure that the requests in a wait can occur
  in any order.

  Run with 2 processes.
  */

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

#if defined(NEEDS_STDLIB_PROTOTYPES)
#include "protofix.h"
#endif

void Pause( double );

void Pause( double sec )
{
  double t1 = MPI_Wtime();
  while (MPI_Wtime() - t1 < sec) ;
}

int main( int argc, char **argv )
{
  int size, rank, flag, i;
  int *buf1, *buf2, cnt;
  double t0;
  MPI_Status statuses[2];
  MPI_Request req[2];

  MPI_Init( &argc, &argv );
  MPI_Comm_size( MPI_COMM_WORLD, &size );
  MPI_Comm_rank( MPI_COMM_WORLD, &rank );

  if (size < 2) {
    printf( "This test requires at least 2 processors\n" );
    MPI_Abort( MPI_COMM_WORLD, 1 );
    return 1;
  }
  
  /* Large enough that almost certainly a rendezvous algorithm will be used
     by Issend.  buflimit.c will give you a more reliable value */
  cnt = 35000;

  /* Test:
     process 0                        process 1
                                      Irecv1
                                      Irecv2
     Sendrecv                         Sendrecv
     pause(2 sec)                     pause(2 sec)
     Issend2                          Waitall
     test(2) for 5 secs
     Ssend1
     Wait(2) if necessary

     If the test for Issend2 never succeeds, then the waitall appears to be
     waiting for req1 first.  By using Issend, we can keep the program from
     hanging.
  */
  buf1 = (int *)malloc( cnt * sizeof(int) );
  buf2 = (int *)malloc( cnt * sizeof(int) );
  if (!buf1 || !buf2) {
    printf( "Could not allocate buffers of size %d\n", cnt );
    MPI_Abort( MPI_COMM_WORLD, 1 );
    return 1;
  }

  for (i=0; i<cnt; i++) {
    buf1[i] = i;
    buf2[i] = i;
  }

  if (rank == 0) {
    MPI_Sendrecv( MPI_BOTTOM, 0, MPI_BYTE, size - 1, 3, 
		  MPI_BOTTOM, 0, MPI_BYTE, size - 1, 3, 
		  MPI_COMM_WORLD, &statuses[0] );
    Pause( 2.0 );
    MPI_Issend( buf2, cnt, MPI_INT, size-1, 2, MPI_COMM_WORLD, &req[0] );
    t0 = MPI_Wtime();
    flag = 0;
    while (t0 + 5.0 > MPI_Wtime() && !flag) 
      MPI_Test( &req[0], &flag, &statuses[0] );
    MPI_Ssend( buf1, cnt, MPI_INT, size-1, 1, MPI_COMM_WORLD );
    if (!flag) {
      printf( 
    "*ERROR: MPI_Waitall appears to be waiting for requests in the order\n\
they appear in the request list\n" );
      MPI_Wait( &req[0], &statuses[0] );
    }
    else {
	printf( "No errors\n" ) ;
    }
  }
  else if (rank == size - 1) {
    MPI_Irecv( buf1, cnt, MPI_INT, 0, 1, MPI_COMM_WORLD, &req[0] );
    MPI_Irecv( buf2, cnt, MPI_INT, 0, 2, MPI_COMM_WORLD, &req[1] );
    MPI_Sendrecv( MPI_BOTTOM, 0, MPI_BYTE, 0, 3, 
		  MPI_BOTTOM, 0, MPI_BYTE, 0, 3, MPI_COMM_WORLD, &statuses[0] );
    Pause( 2.0 );
    MPI_Waitall( 2, req, statuses );
  }

  free( buf1 );
  free( buf2 );
  MPI_Finalize();
  return 0;
}