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MPI_File_get_type_extent.3.rst

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MPI_File_get_type_extent

:ref:`MPI_File_get_type_extent` - Returns the extent of the data type in a file.

SYNTAX

C Syntax

#include <mpi.h>

int MPI_File_get_type_extent(MPI_File fh, MPI_Datatype
     datatype, MPI_Aint *extent)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_GET_TYPE_EXTENT(FH, DATATYPE, EXTENT, IERROR)
     INTEGER FH, DATATYPE, IERROR
     INTEGER(KIND=MPI_ADDRESS_KIND)  EXTENT

Fortran 2008 Syntax

USE mpi_f08
MPI_File_get_type_extent(fh, datatype, extent, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) :: extent
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

  • fh: File handle (handle).
  • datatype: Data type (handle).

OUTPUT PARAMETERS

  • extent: Data type extent (integer).
  • ierror: Fortran only: Error status (integer).

DESCRIPTION

:ref:`MPI_File_get_type_extent` can be used to calculate extent for datatype in the file. The extent is the same for all processes accessing the file associated with fh. If the current view uses a user-defined data representation, :ref:`MPI_File_get_type_extent` uses the dtype_file_extent_fn callback to calculate the extent.

NOTES

If the file data representation is other than "native," care must be taken in constructing etypes and file types. Any of the data-type constructor functions may be used; however, for those functions that accept displacements in bytes, the displacements must be specified in terms of their values in the file for the file data representation being used. MPI will interpret these byte displacements as is; no scaling will be done. The function :ref:`MPI_File_get_type_extent` can be used to calculate the extents of data types in the file. For etypes and file types that are portable data types, MPI will scale any displacements in the data types to match the file data representation. Data types passed as arguments to read/write routines specify the data layout in memory; therefore, they must always be constructed using displacements corresponding to displacements in memory.

ERRORS