Cannot write to /dev/stdout using MPI_File_write_shared

[simonbyrne]

MPICH isn't able to write to /dev/stdout using MPI_File_write_shared (or indeed, any MPI_File_write_XXX operations).

The following code works with Open MPI 4.0.2, but fails with MPICH 3.3.2 on MacOS:

#include <mpi.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char** argv) {
    // Initialize the MPI environment
    MPI_Init(NULL, NULL);

    MPI_File fh;
    MPI_File_open(MPI_COMM_WORLD, "/dev/stdout", MPI_MODE_WRONLY | MPI_MODE_CREATE, MPI_INFO_NULL, &fh);

    char buf[100];
    int rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    snprintf(buf, 100, "hello from rank %d \n", rank);
    MPI_Status status;
    MPI_File_write_shared(fh, buf, strlen(buf), MPI_CHAR, &status);

    MPI_File_close(&fh);

    MPI_Finalize();
}

gives the following error:

├ mpiexec -n 3 ./mpi-stdout
I/O error: Internal MPI error!, error stack:
MPI_FILE_READ_SHARED(98): Could not access shared file pointer
I/O error: Internal MPI error!, error stack:
MPI_FILE_READ_SHARED(98): Could not access shared file pointer