Provided by: openmpi-doc_4.1.6-7ubuntu2_all 
NAME
MPI_Type_create_subarray - Creates a data type describing an n-dimensional subarray of an n-dimensional
array.
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Type_create_subarray(int ndims, const int array_of_sizes[], const int array_of_subsizes[], const int array_of_starts[], int order, MPI_Datatype oldtype, MPI_Datatype *newtype)
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TYPE_CREATE_SUBARRAY(NDIMS, ARRAY_OF_SIZES, ARRAY_OF_SUBSIZES,
ARRAY_OF_STARTS, ORDER, OLDTYPE, NEWTYPE, IERROR)
INTEGER NDIMS, ARRAY_OF_SIZES(*), ARRAY_OF_SUBSIZES(*),
ARRAY_OF_STARTS(*), ORDER, OLDTYPE, NEWTYPE, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Type_create_subarray(ndims, array_of_sizes, array_of_subsizes,
array_of_starts, order, oldtype, newtype, ierror)
INTEGER, INTENT(IN) :: ndims, array_of_sizes(ndims),
array_of_subsizes(ndims), array_of_starts(ndims), order
TYPE(MPI_Datatype), INTENT(IN) :: oldtype
TYPE(MPI_Datatype), INTENT(OUT) :: newtype
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
C++ Syntax
#include <mpi.h>
MPI::Datatype MPI::Datatype::Create_subarray(int ndims,
const int array_of_sizes[], const int array_of_subsizes[],
const int array_of_starts[], int order) const
INPUT PARAMETERS
ndims Number of array dimensions (positive integer).
array_of_sizes
Number of elements of type oldtype in each dimension of the full array (array of positive
integers).
array_of_subsizes
Number of elements of type oldtype in each dimension of the subarray (array of positive
integers).
array_of_starts
Starting coordinates of the subarray in each dimension (array of nonnegative integers).
order Array storage order flag (state).
oldtype Array element data type (handle).
OUTPUT PARAMETERS
newtype New data type (handle).
IERROR Fortran only: Error status (integer).
DESCRIPTION
The subarray type constructor creates an MPI data type describing an n-dimensional subarray of an n-
dimensional array. The subarray may be situated anywhere within the full array, and may be of any nonzero
size up to the size of the larger array as long as it is confined within this array. This type
constructor facilitates creating file types to access arrays distributed in blocks among processes to a
single file that contains the global array.
This type constructor can handle arrays with an arbitrary number of dimensions and works for both C- and
Fortran-ordered matrices (that is, row-major or column-major). Note that a C program may use Fortran
order and a Fortran program may use C order.
The ndims parameter specifies the number of dimensions in the full data array and gives the number of
elements in array_of_sizes, array_of_subsizes, and array_of_starts.
The number of elements of type oldtype in each dimension of the n-dimensional array and the requested
subarray are specified by array_of_sizes and array_of_subsizes, respectively. For any dimension i, it is
erroneous to specify array_of_subsizes[i] < 1 or array_of_subsizes[i] > array of sizes[i].
The array_of_starts contains the starting coordinates of each dimension of the subarray. Arrays are
assumed to be indexed starting from zero. For any dimension i, it is erroneous to specify
array_of_starts[i] < 0
or
array_of_starts[i] > (array_of_sizes[i] - array_of_subsizes[i]).
The order argument specifies the storage order for the subarray as well as the full array. It must be set
to one of the following:
- MPI_ORDER_C: The ordering used by C arrays, (that is, row-major order)
- MPI_ORDER_FORTRAN: The ordering used by Fortran arrays, (that is, column-major order)
A ndims-dimensional subarray (newtype) with no extra padding can be defined by the function Subarray() as
follows:
newtype = Subarray(ndims, {size , size ,..., size },
0 1 ndims-1
{subsize , subsize , ..., subsize },
0 1 ndims-1
{start , start , ..., start }, oldtype)
0 1 ndims-1
Let the typemap of oldtype have the form:
{(type , disp ), (type , disp ), ..., (type , disp )}
0 0 1 1 n-1 n-1
where typei is a predefined MPI data type, and let ex be the extent of oldtype.
The Subarray() function is defined recursively in three equations on page 72 of the MPI-2 standard.
For an example use of MPI_Type_create_subarray in the context of I/O, see Section 9.9.2 of the MPI-2
standard.
NOTES
In a Fortran program with arrays indexed starting from 1, if the starting coordinate of a particular
dimension of the subarray is n, then the entry in array of starts for that dimension is n-1.
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.
4.1.6 Sep 30, 2023 MPI_Type_create_subarray(3)