mpi_file_get_type_extent.3

MPI stands for the Message Passing Interface. Written by the MPI Forum (a large committee comprising

.\"Copyright 2006, Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.TH MPI_File_get_type_extent 3OpenMPI "September 2006" "Open MPI 1.2" " "
.SH NAME
\fBMPI_File_get_type_extent\fP \- Returns the extent of the data type in a file. 

.SH SYNTAX
.ft R
.nf
C Syntax
    #include <mpi.h>
    int MPI_File_get_type_extent(MPI_File \fIfh\fP, MPI_Datatype 
    	      \fIdatatype\fP, MPI_Aint \fI*extent\fP)

Fortran Syntax (see FORTRAN 77 NOTES)
    INCLUDE 'mpif.h'
    MPI_FILE_GET_TYPE_EXTENT(\fIFH\fP, \fIDATATYPE\fP, \fIEXTENT\fP, \fI IERROR\fP)
        	INTEGER	\fIFH, DATATYPE, IERROR\fP
		INTEGER(KIND=MPI_ADDRESS_KIND) \fIEXTENT\fP 

.SH C++ Syntax
.nf
#include <mpi.h>
MPI::Aint MPI::File::Get_type_extent(const MPI::Datatype& 
	\fIdatatype\fP) const

.SH INPUT PARAMETERS
.ft R
.TP 1i
fh
File handle (handle).
.ft R
.TP 1i
datatype
Data type (handle).


.SH OUTPUT PARAMETERS
.ft R
.TP 1i
extent
Data type extent (integer). 
.TP 1i
IERROR
Fortran only: Error status (integer). 

.SH DESCRIPTION
.ft R
MPI_File_get_type_extent can be used to calculate \fIextent\fP for \fIdatatype\fP in the file. The extent is the same for all processes accessing the file associated with \fIfh\fP. If the current view uses a user-defined data representation, MPI_File_get_type_extent uses the \fIdtype_file_extent_fn\fP callback to calculate the extent. 

.SH FORTRAN 77 NOTES
.ft R
The MPI standard prescribes portable Fortran syntax for
the \fIEXTENT\fP argument only for Fortran 90. FORTRAN 77
users may use the non-portable syntax
.sp
.nf
     INTEGER*MPI_ADDRESS_KIND \fIEXTENT\fP
.fi
.sp
where MPI_ADDRESS_KIND is a constant defined in mpif.h
and gives the length of the declared integer in bytes.

.SH NOTES
.ft R
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. 

.SH 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.
.sp
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.  

' @(#)MPI_File_get_type_extent.3 1.22 06/03/09