int MPI_Group_range_incl(
  MPI_Group group,
  int n,
  int ranges[][3], 
  MPI_Group *newgroup
);

Parameters

group

[in] group (handle)

n

[in] number of triplets in array ranges (integer)

ranges

[in] a one-dimensional array of integer triplets, of the form (first rank, last rank, stride) indicating ranks in group or processes to be included in newgroup.

newgroup

[out] new group derived from above, in the order defined by ranges (handle)

Remarks

If ranges consist of the triplets

then newgroup consists of the sequence of processes in group with ranks

Each computed rank must be a valid rank in group and all computed ranks must be distinct, or else the program is erroneous. Note that we may have first_i > last_i, and stride_i may be negative, but cannot be zero.

The functionality of this routine is specified to be equivalent to expanding the array of ranges to an array of the included ranks and passing the resulting array of ranks and other arguments to MPI_GROUP_INCL. A call to MPI_GROUP_INCL is equivalent to a call to MPI_GROUP_RANGE_INCL with each rank i in ranks replaced by the triplet (i,i,1) in the argument ranges.

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 malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

Notes for Fortran

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in 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_GROUP

Null or invalid group passed to function.

MPI_ERR_INTERN

This error is returned when some part of the MPICH implementation is unable to acquire memory.

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_RANK

Invalid source or destination rank. Ranks must be between zero and the size of the communicator minus one; ranks in a receive (MPI_Recv, MPI_Irecv, MPI_Sendrecv, etc.) may also be MPI_ANY_SOURCE.

See Also

Example Code

The following sample code illustrates MPI_Group_range_incl.

#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
 
int main( int argc, char *argv[] )
{
    MPI_Group g1, g2, g4, g5, g45, selfgroup, g6;
    int ranks[16], size, rank, myrank, range[1][3];
    int errs = 0;
    int i, rin[16], rout[16], result;
 
    MPI_Init(0,0);
 
    MPI_Comm_group( MPI_COMM_WORLD, &g1 );
    MPI_Comm_rank( MPI_COMM_WORLD, &myrank );
    MPI_Comm_size( MPI_COMM_WORLD, &size );
    if (size < 8) {
        fprintf( stderr, "Test requires 8 processes (16 prefered) only %d provided\n", size ); fflush(stdout);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }
 
    /* 16 members, this process is rank 0, return in group 1 */
    ranks[0] = myrank; ranks[1] = 2; ranks[2] = 7;
    if (myrank == 2) ranks[1] = 3;
    if (myrank == 7) ranks[2] = 6;
    MPI_Group_incl( g1, 3, ranks, &g2 );
 
    /* Check the resulting group */
    MPI_Group_size( g2, &size );
    MPI_Group_rank( g2, &rank );
 
    if (size != 3) {
        fprintf( stderr, "Size should be %d, is %d\n", 3, size );fflush(stderr);
        errs++;
    }
    if (rank != 0) {
        fprintf( stderr, "Rank should be %d, is %d\n", 0, rank );fflush(stderr);
        errs++;
    }
 
    rin[0] = 0; rin[1] = 1; rin[2] = 2;
    MPI_Group_translate_ranks( g2, 3, rin, g1, rout );
    for (i=0; i<3; i++) {
        if (rout[i] != ranks[i]) {
            fprintf( stderr, "translated rank[%d] %d should be %d\n", i, rout[i], ranks[i] );fflush(stderr);
            errs++;
        }
    }
 
    /* Translate the process of the self group against another group */
    MPI_Comm_group( MPI_COMM_SELF, &selfgroup );
    rin[0] = 0;
    MPI_Group_translate_ranks( selfgroup, 1, rin, g1, rout );
    if (rout[0] != myrank) {
        fprintf( stderr, "translated of self is %d should be %d\n", rout[0], myrank );fflush(stderr);
        errs++;
    }
 
    for (i=0; i<size; i++)
        rin[i] = i;
    MPI_Group_translate_ranks( g1, size, rin, selfgroup, rout );
    for (i=0; i<size; i++) {
        if (i == myrank && rout[i] != 0) {
            fprintf( stderr, "translated world to self of %d is %d\n", i, rout[i] );fflush(stderr);
            errs++;
        }
        else if (i != myrank && rout[i] != MPI_UNDEFINED) {
            fprintf( stderr, "translated world to self of %d should be undefined, is %d\n", i, rout[i] );
            errs++;
        }
    }
    MPI_Group_free( &selfgroup );
 
    /* Exclude everyone in our group */
    {
        int i, *ranks, g1size;
 
        MPI_Group_size( g1, &g1size );
 
        ranks = (int *)malloc( g1size * sizeof(int) );
        for (i=0; i<g1size; i++) ranks[i] = i;
        MPI_Group_excl( g1, g1size, ranks, &g6 );
        if (g6 != MPI_GROUP_EMPTY) {
            fprintf( stderr, "Group formed by excluding all ranks not empty\n" );fflush(stderr);
            errs++;
            MPI_Group_free( &g6 );
        }
        free( ranks );
    }
 
    MPI_Group_free( &g2 );
 
    range[0][0] = 1;
    range[0][1] = size-1;
    range[0][2] = 2;
    MPI_Group_range_excl( g1, 1, range, &g5 );
 
    range[0][0] = 1;
    range[0][1] = size-1;
    range[0][2] = 2;
    MPI_Group_range_incl( g1, 1, range, &g4 );
 
    MPI_Group_union( g4, g5, &g45 );
 
    MPI_Group_compare( MPI_GROUP_EMPTY, g4, &result );
    if (result != MPI_UNEQUAL) {
        errs++;
        fprintf( stderr, "Comparison with empty group gave %d, not 3\n", result );fflush(stderr);
    }
    MPI_Group_free( &g4 );
    MPI_Group_free( &g5 );
    MPI_Group_free( &g45 );
 
    /* Now, duplicate the test, but using negative strides */
    range[0][0] = size-1;
    range[0][1] = 1;
    range[0][2] = -2;
    MPI_Group_range_excl( g1, 1, range, &g5 );
 
    range[0][0] = size-1;
    range[0][1] = 1;
    range[0][2] = -2;
    MPI_Group_range_incl( g1, 1, range, &g4 );
 
    MPI_Group_union( g4, g5, &g45 );
 
    MPI_Group_compare( MPI_GROUP_EMPTY, g4, &result );
    if (result != MPI_UNEQUAL) {
        errs++;
        fprintf( stderr, "Comparison with empty group (formed with negative strides) gave %d, not 3\n", result );fflush(stderr);
    }
    MPI_Group_free( &g4 );
    MPI_Group_free( &g5 );
    MPI_Group_free( &g45 );
    MPI_Group_free( &g1 );
 
    MPI_Finalize();
    return 0;
}