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MPI_File_get_type_extent(3) man page (version 1.10.1)

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


C Syntax
    #include <mpi.h>
    int MPI_File_get_type_extent(MPI_File fh, MPI_Datatype
              datatype, MPI_Aint *extent)

Fortran Syntax (see FORTRAN 77 NOTES)

    INCLUDE ’mpif.h’

C++ Syntax

#include <mpi.h>
MPI::Aint MPI::File::Get_type_extent(const MPI::Datatype&
    datatype) const

Input Parameters

File handle (handle).
Data type (handle).

Output Parameters

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


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, MPI_File_get_type_extent uses the dtype_file_extent_fn callback to calculate the extent.

Fortran 77 Notes

The MPI standard prescribes portable Fortran syntax for the EXTENT argument only for Fortran 90. FORTRAN 77 users may use the non-portable syntax


where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes.


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 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.


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. For MPI I/O function errors, the default error handler is set to MPI_ERRORS_RETURN. The error handler may be changed with MPI_File_set_errhandler; the predefined error handler MPI_ERRORS_ARE_FATAL may be used to make I/O errors fatal. Note that MPI does not guarantee that an MPI program can continue past an error.

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