# MPI_Type_vector

## NAME

MPI_Type_vector − Creates a vector (strided) datatype.

## 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.

## ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI:Exception object.

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.

## SEE ALSO

MPI_Type_create_hvector
MPI_Type_hvector

MPI API Index