.\"Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.TH MPI_Type_get_true_extent 3 "Dec 08, 2009" "1.4" "Open MPI"
.SH NAME
\fBMPI_Type_get_true_extent\fP \- Returns the true lower bound and extent of a data type's corresponding typemap, ignoring MPI_UB and MPI_LB markers. 

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Type_get_true_extent(MPI_Datatype \fIdatatype\fP, 
	MPI_Aint *\fItrue_lb\fP, MPI_Aint *\fItrue_extent\fP)

.SH Fortran Syntax (see FORTRAN 77 NOTES)
.nf
INCLUDE 'mpif.h'
MPI_TYPE_GET_TRUE_EXTENT(\fIDATATYPE, TRUE_LB, TRUE_EXTENT, IERROR\fP)
	INTEGER	\fIDATATYPE, IERROR\fP 
	INTEGER(KIND=MPI_ADDRESS_KIND) \fITRUE_LB, TRUE_EXTENT\fP

.SH C++ Syntax
.nf
#include <mpi.h>
void MPI::Datatype::Get_true_extent(MPI::Aint& \fItrue_lb\fP, 
	MPI::Aint& \fItrue_extent\fP) const

.SH INPUT PARAMETER
.ft R
.TP 1i
datatype      
Data type for which information is wanted (handle).
.sp
.SH OUTPUT PARAMETERS
.ft R
.TP 1i
true_lb
True lower bound of data type (integer).
.TP 1i
true_extent
True size of data type (integer).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer). 

.SH DESCRIPTION
.ft R
The \fItrue_lb\fP parameter returns the offset of the lowest unit of store that is addressed by the data type, that is, the lower bound of the corresponding typemap, ignoring MPI_LB markers. The \fItrue_extent\fP parameter returns the true size of the data type, that is, the extent of the corresponding typemap, ignoring MPI_LB and MPI_UB markers, and performing no rounding for alignment. 
.sp
The \fItrue_extent\fP is the minimum number of bytes of memory necessary to hold a data type, uncompressed.
.sp
See Section 4.14.3 of the MPI-2 standard for more detailed definitions of these parameters in relation to the typemap. 

.SH FORTRAN 77 NOTES
.ft R
The MPI standard prescribes portable Fortran syntax for
the \fITRUE_LB\fP and \fITRUE_EXTENT\fP arguments only for Fortran 90. FORTRAN 77
users may use the non-portable syntax
.sp
.nf
     INTEGER*MPI_ADDRESS_KIND \fITRUE_LB\fP
or
     INTEGER*MPI_ADDRESS_KIND \fITRUE_EXTENT\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 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. 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.