SYNTAX

C Syntax

#include <mpi.h>
int MPI_Type_vector(int count, int blocklength, int stride,
        MPI_Datatype oldtype, MPI_Datatype *newtype)

Fortran Syntax

INCLUDE 'mpif.h'
MPI_TYPE_VECTOR(COUNT, BLOCKLENGTH, STRIDE, OLDTYPE, NEWTYPE,
                IERROR)
        INTEGER COUNT, BLOCKLENGTH, STRIDE, OLDTYPE 
        INTEGER NEWTYPE, IERROR 

C++ Syntax

#include <mpi.h>
Datatype Datatype::Create_vector(int count, int blocklength, 
        int stride) const

INPUT PARAMETERS

count

Number of blocks (nonnegative integer).

blocklength

Number of elements in each block (nonnegative integer).

stride

Number of elements between start of each block (integer).

oldtype

Old datatype (handle).

OUTPUT PARAMETERS

newtype

New datatype (handle).

IERROR

Fortran only: Error status (integer).

DESCRIPTION

The function MPI_Type_vector is a 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 1: Assume, again, that oldtype has type map {(double, 0), (char, 8)}, with extent 16. A call to MPI_Type_vector(2, 3, 4, oldtype, newtype) will create the datatype with type map

    {(double, 0), (char, 8), (double, 16), (char, 24), 
    (double, 32), (char, 40), 
    (double, 64), (char, 72), 
    (double, 80), (char, 88), (double, 96), (char, 104)}

That is, two blocks with three copies each of the old type, with a stride of 4 elements (4 x 6 bytes) between the blocks.

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

    {(double, 0), (char, 8), (double, -32), (char, -24), 
    (double, -64), (char, -56)}

In general, assume that oldtype has type map

    {(type(0), disp(0)), ..., (type(n-1), disp(n-1))},

with extent ex. Let bl be the blocklength. The newly created datatype has a type map with count x bl x n entries:

    {(type(0), disp(0)), ..., (type(n-1), disp(n-1)),
    (type(0), disp(0) + ex), ..., (type(n-1), disp(n-1) + ex), ...,
    (type(0), disp(0) + (bl -1) * ex),..., 
    (type(n-1), disp(n-1) + (bl -1)* ex),
    (type(0), disp(0) + stride * ex),..., (type(n-1), 
    disp(n-1) + stride * ex), ...,
    (type(0), disp(0) + (stride + bl - 1) * ex), ..., 
    (type(n-1), disp(n-1) + (stride + bl -1) * ex), ...,
    (type(0), disp(0) + stride * (count -1) * ex), ...,
    (type(n-1), disp(n-1) + stride * (count -1) * ex), ...,
    (type(0), disp(0) + (stride * (count -1) + bl -1) * ex), ...,
    (type(n-1), disp(n-1) + (stride * (count -1) + bl -1) * ex)}

A call to MPI_Type_contiguous(count, oldtype, newtype) is equivalent to a call to MPI_Type_vector(count, 1, 1, oldtype, newtype), or to a call to MPI_Type_vector(1, count, n, oldtype, newtype), n arbitrary.