The Great and Terrible implementation of MPI-2

function index


Creates a vector (strided) datatype
int MPI_Type_vector(
  int count,
  int blocklength,
  int stride,
  MPI_Datatype old_type,
  MPI_Datatype *newtype_p


[in] number of blocks (nonnegative integer)
[in] number of elements in each block (nonnegative integer)
[in] number of elements between start of each block (integer)
[in] old datatype (handle)
[out] new datatype (handle)


The function MPI_TYPE_VECTOR is a more general constructor that allows replication of a datatype into locations that consist of equally spaced blocks. Each block is obtained by concatenating the same number of copies of the old datatype. The spacing between blocks is a multiple of the extent of the old datatype.

Example Assume, again, that oldtype has type map with extent 16. A call to MPI_TYPE_VECTOR( 2, 3, 4, oldtype, newtype) will create the datatype with type map,


That is, two blocks with three copies each of the old type, with a stride of 4 elements ( bytes) between the blocks.

Example A call to MPI_TYPE_VECTOR(3, 1, -2, oldtype, newtype) will create the datatype,


In general, assume that oldtype has type map,

with extent ex. Let bl be the blocklength. The newly created datatype has a type map with










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 routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is 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 INTEGER in Fortran.


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.

No error; MPI routine completed successfully.

Example Code

The following sample code illustrates MPI_Type_vector.

#include "mpi.h"
#include <stdio.h>

int main(int argc, char *argv[])
    int rank, size, i;
    MPI_Datatype type, type2;
    int buffer[24];
    MPI_Status status;

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

    MPI_Type_contiguous(3, MPI_INT, &type2);
    MPI_Type_vector(3, 2, 3, type2, &type);

    if (rank == 0)
        for (i=0; i<24; i++)
            buffer[i] = i;
        MPI_Send(buffer, 1, type, 1, 123, MPI_COMM_WORLD);

    if (rank == 1)
        for (i=0; i<24; i++)
            buffer[i] = -1;
        MPI_Recv(buffer, 1, type, 0, 123, MPI_COMM_WORLD, &status);
        for (i=0; i<24; i++)
            printf("buffer[%d] = %d\n", i, buffer[i]);

    return 0;