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.