plucky (3) MPI_Type_create_subarray.openmpi.3.gz
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
• 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_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:
• MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.
• 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.
• MPI_ERRORS_RETURN Returns an error code to the application.
MPI applications can also implement their own error handlers by calling:
• MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
• MPI_File_create_errhandler then MPI_File_set_errhandler
• MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
• 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
Feb 17, 2025 MPI_TYPE_CREATE_SUBARRAY(3)