[mpich-discuss] MPICH2 for Win: Topology functions

[Alejandro Allievi]

Hi,

I'm setting up a grid topology and associated communicator using the
function Setup_grid below. It works fine for process zero but throws:

Fatal error in PMPI_Comm_rank: Invalid communicator, error stack:
PMPI_Comm_rank(109): MPI_Comm_rank(MPI_COMM_NULL, rank=000000000022FE4C) failed
PMPI_Comm_rank(66).: Null communicator

Does MPICH2 for Win7 support topology functions???

Thanks for any help.

Alejandro

************CODE BELOW***************************
void Setup_grid(GRID_INFO_T*  grid  /* out */) {
    int old_rank;
    int dimensions[2];
    int wrap_around[2];
    int coordinates[2];
    int free_coords[2];


    /* Set up Global Grid Information */
    MPI_Comm_size(MPI_COMM_WORLD, &(grid->p));
    MPI_Comm_rank(MPI_COMM_WORLD, &old_rank);

    printf("Process %d of %d inside Setup_Grid\n", old_rank, grid->p);

    /* We assume p is a perfect square */
    grid->q = (int) sqrt((double) grid->p);
    dimensions[0] = dimensions[1] = grid->q;

    /* We want a circular shift in second dimension. */
    /* Don't care about first                        */
    wrap_around[0] = wrap_around[1] = 1;
    MPI_Cart_create(MPI_COMM_WORLD, 2, dimensions,
    		wrap_around, 1, &(grid->comm));

    MPI_Comm_rank(grid->comm, &(grid->my_rank));
    MPI_Cart_coords(grid->comm, grid->my_rank, 2, coordinates);
    grid->my_row = coordinates[0];
    grid->my_col = coordinates[1];

    /* Set up row communicators */
    free_coords[0] = 0;
    free_coords[1] = 1;
    MPI_Cart_sub(grid->comm, free_coords, &(grid->row_comm));

    /* Set up column communicators */
    free_coords[0] = 1;
    free_coords[1] = 0;
    MPI_Cart_sub(grid->comm, free_coords, &(grid->col_comm));

    printf("Process %d leaving Setup_Grid\n", old_rank);

} /* Setup_grid */

-- 
Alejandro Allievi
http://www.ace-net.ca/wiki/Alejandro_Allievi

"Tenez, mon ami, si vous y pensez bien, vous trouverez qu'en tout,
notre véritable sentiment n'est pas celui dans lequel nous n'avons
jamais vacillé; mais celui auquel nous sommes le plus habituellement
revenus". Denis Diderot.

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