ictest.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.

/* -*- Mode: C; c-basic-offset:4 ; -*- */
/* ictest.c */
#include <stdio.h>
#include "mpi.h"
#include "test.h"

int verbose = 0;

int main( int argc, char **argv )
{
  int size, rank, key, his_key, lrank, result;
  MPI_Comm myComm;
  MPI_Comm myFirstComm;
  MPI_Comm mySecondComm;
  int errors = 0, sum_errors;
  MPI_Status status;
  
  /* Initialization */
  MPI_Init ( &argc, &argv );
  MPI_Comm_rank ( MPI_COMM_WORLD, &rank);
  MPI_Comm_size ( MPI_COMM_WORLD, &size);

  /* Only works for 2 or more processes */
  if (size >= 2) {
    MPI_Comm merge1, merge2, merge3, merge4;

    /* Generate membership key in the range [0,1] */
    key = rank % 2;
    
    MPI_Comm_split ( MPI_COMM_WORLD, key, rank, &myComm );
    /* This creates an intercomm that is the size of comm world 
       but has processes grouped by even and odd */
    MPI_Intercomm_create (myComm, 0, MPI_COMM_WORLD, (key+1)%2, 1, 
                          &myFirstComm );
    /* Dup an intercomm */
    MPI_Comm_dup ( myFirstComm, &mySecondComm );
    MPI_Comm_rank( mySecondComm, &lrank );
    his_key = -1;
    
    /* Leaders communicate with each other */
    if (lrank == 0) {
      MPI_Sendrecv (&key,     1, MPI_INT, 0, 0,
                    &his_key, 1, MPI_INT, 0, 0, mySecondComm, &status);
      if (key != (his_key+1)%2) {
	  printf( "Received %d but expected %d\n", his_key, (his_key+1)%2 );
	  errors++;
      }
    }
    
    if (errors)
      printf("[%d] Failed!\n",rank);

    if (verbose) printf( "About to merge intercommunicators\n" );
    MPI_Intercomm_merge ( mySecondComm, key, &merge1 );
    MPI_Intercomm_merge ( mySecondComm, (key+1)%2, &merge2 );
    MPI_Intercomm_merge ( mySecondComm, 0, &merge3 );
    MPI_Intercomm_merge ( mySecondComm, 1, &merge4 );

    /* We should check that these are correct!  An easy test is that
       the merged comms are all MPI_SIMILAR (unless 2 processes used, 
       in which case MPI_CONGRUENT is ok */
    MPI_Comm_compare( merge1, MPI_COMM_WORLD, &result );
    if ((size > 2 && result != MPI_SIMILAR) ||
	(size == 2 && result != MPI_CONGRUENT)) {
	errors ++;
	printf( "merge1 is not the same size as comm world\n" );
    }
    /* merge 2 isn't ordered the same way as the others, even for 2 processes */
    MPI_Comm_compare( merge2, MPI_COMM_WORLD, &result );
    if (result != MPI_SIMILAR) {
	errors ++;
	printf( "merge2 is not the same size as comm world\n" );
    }
    MPI_Comm_compare( merge3, MPI_COMM_WORLD, &result );
    if ((size > 2 && result != MPI_SIMILAR) ||
	(size == 2 && result != MPI_CONGRUENT)) {
	errors ++;
	printf( "merge3 is not the same size as comm world\n" );
    }
    MPI_Comm_compare( merge4, MPI_COMM_WORLD, &result );
    if ((size > 2 && result != MPI_SIMILAR) ||
	(size == 2 && result != MPI_CONGRUENT)) {
	errors ++;
	printf( "merge4 is not the same size as comm world\n" );
    }

    /* Free communicators */
    if (verbose) printf( "About to free communicators\n" );
    MPI_Comm_free( &myComm );
    MPI_Comm_free( &myFirstComm );
    MPI_Comm_free( &mySecondComm );
    MPI_Comm_free( &merge1 );
    MPI_Comm_free( &merge2 );
    MPI_Comm_free( &merge3 );
    MPI_Comm_free( &merge4 );
  }
  else {
      errors ++;
      printf("[%d] Failed - at least 2 nodes must be used\n",rank);
  }

  MPI_Barrier( MPI_COMM_WORLD );
  MPI_Allreduce( &errors, &sum_errors, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD );
  if (sum_errors > 0) {
      printf( "%d errors on process %d\n", errors, rank );
      }
  else if (rank == 0) {
      printf( " No Errors\n" );
      }
  /* Finalize and end! */

  MPI_Finalize();
  return 0;
}