17.2.416. MPI_Type_vector

MPI_Type_vector - Creates a vector (strided) datatype.

17.2.416.1. SYNTAX

17.2.416.1.1. C Syntax

#include <mpi.h>

int MPI_Type_vector(int count, int blocklength, int stride,
     MPI_Datatype oldtype, MPI_Datatype *newtype)

17.2.416.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TYPE_VECTOR(COUNT, BLOCKLENGTH, STRIDE, OLDTYPE, NEWTYPE,
             IERROR)
     INTEGER COUNT, BLOCKLENGTH, STRIDE, OLDTYPE
     INTEGER NEWTYPE, IERROR

17.2.416.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Type_vector(count, blocklength, stride, oldtype, newtype, ierror)
     INTEGER, INTENT(IN) :: count, blocklength, stride
     TYPE(MPI_Datatype), INTENT(IN) :: oldtype
     TYPE(MPI_Datatype), INTENT(OUT) :: newtype
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.416.2. 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).

17.2.416.3. OUTPUT PARAMETERS

  • newtype: New datatype (handle).

  • IERROR: Fortran only: Error status (integer).

17.2.416.4. 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 16 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.

17.2.416.5. ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.