probe1.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.

/* 
   This is a test of probe to receive a message of unknown type (used as a
   server)
 */
#include <stdio.h>
#include <string.h>
#include "mpi.h"
#include "test.h"

int main( int argc, char **argv ) 
{
int data, to, from, tag, maxlen, np, myid, flag, dest, src;
MPI_Status status, status1;

MPI_Init( &argc, &argv );
MPI_Comm_rank( MPI_COMM_WORLD, &myid );
MPI_Comm_size( MPI_COMM_WORLD, &np );

/* dest writes out the received stats; for the output to be
   consistant (with the final check), it should be procees 0 */
if (argc > 1 && argv[1] && strcmp( "-alt", argv[1] ) == 0) {
    dest = np - 1;
    src  = 0;
    }
else {
    src  = np - 1;
    dest = 0;
    }

if (myid == src) {
    to   = dest;
    tag = 2000;
#ifdef VERBOSE
    printf( "About to send\n" );
#endif
    MPI_Send( &data, 1, MPI_INT, to, tag, MPI_COMM_WORLD );
    tag = 2001;
#ifdef VERBOSE
    printf( "About to send 'done'\n" );
#endif
    MPI_Send( &data, 1, MPI_INT, to, tag, MPI_COMM_WORLD );
    }
else {
    /* Server loop */
    while (1) {
	tag    = MPI_ANY_TAG;
	from   = MPI_ANY_SOURCE;
	/* Should really use MPI_Probe, but functionally this will work
	   (it is less efficient, however) */
	do {		
	    MPI_Iprobe( from, tag, MPI_COMM_WORLD, &flag, &status );
	    } while (!flag);
	if (status.MPI_TAG == 2001) {
#ifdef VERBOSE
	    printf( "Received terminate message\n" );
#endif
	    /* Actually need to receive it ... */
	    MPI_Recv( &data, 1, MPI_INT, status.MPI_SOURCE, 
		      status.MPI_TAG, MPI_COMM_WORLD, &status1 );
	    break;
	    }
	if (status.MPI_TAG == 2000) {
	    MPI_Get_count( &status, MPI_INT, &maxlen );
	    if (maxlen > 1)
		printf( "Error; size = %d\n", maxlen );
#ifdef VERBOSE
	    printf( "About to receive\n" );
#endif
	    MPI_Recv( &data, 1, MPI_INT, status.MPI_SOURCE, 
		      status.MPI_TAG, MPI_COMM_WORLD, &status1 );
	    }
	}
    }
MPI_Barrier( MPI_COMM_WORLD );
Test_Waitforall( );
MPI_Finalize();
return 0;
}