DeinoMPI

The Great and Terrible implementation of MPI-2

MPI_Win_get_group

Get the MPI Group of the window object

int MPI_Win_get_group(
  MPI_Win win,
  MPI_Group *group
);

Parameters

win: [in] window object (handle)
group: [out] group of processes which share access to the window (handle)

Remarks

MPI_WIN_GET_GROUP returns a duplicate of the group of the communicator used to create the window. associated with win. The group is returned in group.

The group is a duplicate of the group from the communicator used to create the MPI window, and should be freed with MPI_Group_free when it is no longer needed. This group can be used to form the group of neighbors for the routines MPI_Win_post and MPI_Win_start.

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as mallocor other non-MPICH runtime routines that are themselves not interrupt-safe.

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierris an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGERin Fortran.

Errors

All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS: No error; MPI routine completed successfully.

MPI_ERR_WIN: Invalid MPI window object

MPI_ERR_ARG: Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).

MPI_ERR_OTHER: Other error; use MPI_Error_string to get more information about this error code.

Example Code

The following sample code illustrates MPI_Win_get_group.

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

/* Test of Win_get_group */

int main( int argc, char *argv[] )
{
    int errs = 0;
    int result;
    int buf[10];
    MPI_Win   win;
    MPI_Group group, wingroup;
    int minsize = 2;
    MPI_Comm      comm;

    MPI_Init( &argc, &argv );

    comm = MPI_COMM_WORLD;
    MPI_Win_create( buf, sizeof(int) * 10, sizeof(int), MPI_INFO_NULL, comm, &win );
    MPI_Win_get_group( win, &wingroup );
    MPI_Comm_group( comm, &group );
    MPI_Group_compare( group, wingroup, &result );
    if (result != MPI_IDENT) {
        errs++;
        fprintf( stderr, "Group returned by Win_get_group not the same as the input group\n" );fflush(stderr);
    }
    MPI_Group_free( &wingroup );
    MPI_Group_free( &group );
    MPI_Win_free( &win );

    MPI_Finalize();
    return errs;
}

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