DeinoMPI

The Great and Terrible implementation of MPI-2

MPI_Type_create_hindexed

Create a datatype for an indexed datatype with displacements in bytes

int MPI_Type_create_hindexed(
  int count,
  int blocklengths[],
  MPI_Aint displacements[],
  MPI_Datatype oldtype,
  MPI_Datatype *newtype
);

Parameters

count: [in] number of blocks --- also number of entries in displacements and blocklengths (integer)
blocklengths: [in] number of elements in each block (array of nonnegative integers)
displacements: [in] byte displacement of each block (array of integer)
oldtype: [in] old datatype (handle)
newtype: [out] new datatype (handle)

Remarks

The function MPI_TYPE_CREATE_HINDEXED is identical to MPI_TYPE_CREATE_INDEXED, except that block displacements in array_of_displacements are specified in bytes, rather than in multiples of the oldtype extent.

Assume that oldtype has type map,

with extent ex. Let B be the array_of_blocklength argument and D be the
array_of_displacements argument. The newly created datatype has a type map with entries:

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_TYPE: Invalid datatype argument. May be an uncommitted MPI_Datatype (see MPI_Type_commit).

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

Example Code

The following sample code illustrates MPI_Type_create_hindexed.

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

int main(int argc, char *argv[])
{
    int rank, size, i;
    MPI_Datatype type, type2;
    int blocklen[3] = { 2, 3, 1 };
    MPI_Aint displacement[3] = { 0, 7*sizeof(int), 18*sizeof(int) };
    int buffer[21];
    MPI_Status status;

    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    if (size < 2)
    {
        printf("Please run with 2 processes.\n");
        MPI_Finalize();
        return 1;
    }
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    MPI_Type_contiguous(3, MPI_INT, &type2);
    MPI_Type_commit(&type2);
    MPI_Type_create_hindexed(3, blocklen, displacement, type2, &type);
    MPI_Type_commit(&type);

    if (rank == 0)
    {
        for (i=0; i<21; i++)
            buffer[i] = i;
        MPI_Send(buffer, 1, type, 1, 123, MPI_COMM_WORLD);
    }

    if (rank == 1)
    {
        for (i=0; i<21; i++)
            buffer[i] = -1;
        MPI_Recv(buffer, 1, type, 0, 123, MPI_COMM_WORLD, &status);
        for (i=0; i<21; i++)
            printf("buffer[%d] = %d\n", i, buffer[i]);
        fflush(stdout);
    }

    MPI_Finalize();
    return 0;
}

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