MPI_TYPE_CREATE_SUBARRAY(3) Open MPI MPI_TYPE_CREATE_SUBARRAY(3)
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
INPUT PARAMETERS
o ndims: Number of array dimensions (positive integer).
o array_of_sizes: Number of elements of type oldtype in each dimension
of the full array (array of positive integers).
o array_of_subsizes: Number of elements of type oldtype in each
dimension of the subarray (array of positive integers).
o array_of_starts: Starting coordinates of the subarray in each
dimension (array of nonnegative integers).
o order: Array storage order flag (state).
o oldtype: Array element data type (handle).
OUTPUT PARAMETERS
o newtype: New data type (handle).
o 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:
o MPI_ORDER_C: The ordering used by C arrays, (that is, row-major
order)
o 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_0, size_1,..., size_ndims-1},
{subsize_0, subsize_1, ..., subsize_ndims-1},
{start_0, start_1, ..., start_ndims-1}, oldtype)
Let the typemap of oldtype have the form:
{(type_0, disp_0), (type_1, disp_1), ..., (type_n-1, disp_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 return
result of the function and Fortran routines in the last argument.
Before the error value is returned, the current MPI error handler
associated with the communication object (e.g., communicator, window,
file) is called. If no communication object is associated with the MPI
call, then the call is considered attached to MPI_COMM_SELF and will
call the associated MPI error handler. When MPI_COMM_SELF is not
initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize,
or when using the Sessions Model exclusively) the error raises the
initial error handler. The initial error handler can be changed by
calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World
model, or the mpi_initial_errhandler CLI argument to mpiexec or info
key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate
error handler has been set, then the MPI_ERRORS_RETURN error handler is
called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is
called for all other MPI functions.
Open MPI includes three predefined error handlers that can be used:
o MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI
processes.
o MPI_ERRORS_ABORT An error handler that can be invoked on a
communicator, window, file, or session. When called on a
communicator, it acts as if MPI_Abort was called on that
communicator. If called on a window or file, acts as if MPI_Abort was
called on a communicator containing the group of processes in the
corresponding window or file. If called on a session, aborts only the
local process.
o MPI_ERRORS_RETURN Returns an error code to the application.
MPI applications can also implement their own error handlers by
calling:
o MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
o MPI_File_create_errhandler then MPI_File_set_errhandler
o MPI_Session_create_errhandler then MPI_Session_set_errhandler or at
MPI_Session_init
o MPI_Win_create_errhandler then MPI_Win_set_errhandler
Note that MPI does not guarantee that an MPI program can continue past
an error.
See the MPI man page for a full list of MPI error codes.
See the Error Handling section of the MPI-3.1 standard for more
information.
COPYRIGHT
2003-2025, The Open MPI Community
February 14, 2025 MPI_TYPE_CREATE_SUBARRAY(3)