Hi all,
I am trying to test the bandwidth of intra-MPI send and recv. The code is
attached here. When I give the input 2048 (namely each process will send
and receive 2GB data), the program reported:
Read 2147479552, expected 2147483648, errno = 95
Read 2147479552, expected 2147483648, errno = 98
Read 2147479552, expected 2147483648, errno = 98
Read 2147479552, expected 2147483648, errno = 98
Does this mean Openmpi does not support the send and recv where data size
is larger than 2GB, or is there a bug in my code? Thank you.
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
#include <sys/types.h>
#include <unistd.h>
int main(int argc, char *argv[]) {
int count;
float voltage;
int *in;
int i;
int rank, size;
MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
long mb = atol(argv[1]);
count = mb / 4 * 1024 * 1024;
in = (int *)malloc( count * sizeof(int));
for (i = 0; i < count; i++) {
*(in + i) = i;
}
MPI_Barrier(MPI_COMM_WORLD);
float time = MPI_Wtime();
if ((rank & 1) == 0) {
MPI_Send(in, count, MPI_INT, rank + 1, 0, MPI_COMM_WORLD);
} else {
MPI_Status status;
MPI_Recv(in, count, MPI_INT, rank - 1, 0, MPI_COMM_WORLD, &status);
}
if ((rank & 1) == 1) {
MPI_Send(in, count, MPI_INT, rank - 1, 0, MPI_COMM_WORLD);
} else {
MPI_Status status;
MPI_Recv(in, count, MPI_INT, rank + 1, 0, MPI_COMM_WORLD, &status);
}
time = MPI_Wtime() - time;
free( in );
MPI_Finalize();
return 0;
}
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