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/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
* (C) 2008 by Argonne National Laboratory.
* See COPYRIGHT in top-level directory.
*/
#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#define SIZE 100000
#define ITER 1000
#define ERROR_MARGIN 0.5
static int verbose = 0;
int main(int argc, char *argv[])
{
char *sbuf, *rbuf;
int i, j;
double t1, t2, t, ts;
int rank, size;
MPI_Status status;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
if (getenv("MPITEST_VERBOSE"))
verbose = 1;
/* Allocate memory regions to communicate */
sbuf = (char *) malloc(SIZE);
rbuf = (char *) malloc(size * SIZE);
/* Touch the buffers to make sure they are allocated */
for (i = 0; i < SIZE; i++)
sbuf[i] = '0';
for (i = 0; i < SIZE * size; i++)
rbuf[i] = '0';
/* Time when rank 0 gathers the data */
MPI_Barrier(MPI_COMM_WORLD);
t1 = MPI_Wtime();
for (i = 0; i < ITER; i++) {
MPI_Gather(sbuf, SIZE, MPI_BYTE, rbuf, SIZE, MPI_BYTE, 0, MPI_COMM_WORLD);
MPI_Barrier(MPI_COMM_WORLD);
}
t2 = MPI_Wtime();
t = (t2 - t1) / ITER;
/* Time when rank 1 gathers the data */
MPI_Barrier(MPI_COMM_WORLD);
t1 = MPI_Wtime();
for (j = 0; j < ITER; j++) {
MPI_Gather(sbuf, SIZE, MPI_BYTE, rbuf, SIZE, MPI_BYTE, 1, MPI_COMM_WORLD);
MPI_Barrier(MPI_COMM_WORLD);
}
t2 = MPI_Wtime();
ts = (t2 - t1) / ITER;
if (rank == 1)
MPI_Send(&ts, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD);
if (rank == 0)
MPI_Recv(&ts, 1, MPI_DOUBLE, 1, 0, MPI_COMM_WORLD, &status);
/* Print out the results */
if (!rank) {
if ((ts / t) > (1 + ERROR_MARGIN)) { /* If the difference is more than 10%, it's an error */
printf("%.3f\t%.3f\n", 1000000.0 * ts, 1000000.0 * t);
printf("Too much difference in performance\n");
} else
printf(" No Errors\n");
}
MPI_Finalize();
return 0;
}
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