--- /dev/null
+/* -*- 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;
+}