MPI_Type_create_subarray(3) Open MPI MPI_Type_create_subarray(3)NAMEMPI_Type_create_subarray - Creates a data type describing an n-dimen‐
sional subarray of an n-dimensional array.
SYNTAXC 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
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
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_sub‐
sizes, 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_sub‐
sizes[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 start‐
ing 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++ func‐
tions 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.
1.7.4 Feb 04, 2014 MPI_Type_create_subarray(3)
