io0.c

The example for Boor USING MPI2

/* example of sequential Unix write into a common file */
#include "mpi.h"
#include <stdio.h>
#define BUFSIZE 100

int main(int argc, char *argv[])
{
    int i, myrank, numprocs, buf[BUFSIZE];
    MPI_Status status;
    FILE *myfile;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    for (i=0; i<BUFSIZE; i++)	
	buf[i] = myrank * BUFSIZE + i;
    if (myrank != 0)
	MPI_Send(buf, BUFSIZE, MPI_INT, 0, 99, MPI_COMM_WORLD);
    else {
	myfile = fopen("testfile", "w");
	fwrite(buf, sizeof(int), BUFSIZE, myfile);
	for (i=1; i<numprocs; i++) {
	    MPI_Recv(buf, BUFSIZE, MPI_INT, i, 99, MPI_COMM_WORLD,
		     &status);
	    fwrite(buf, sizeof(int), BUFSIZE, myfile);
	}
	fclose(myfile);
    }
    MPI_Finalize();
    return 0;
}