MPI_Buffer_attach(3) Open MPI MPI_Buffer_attach(3)
NAME
MPI_Buffer_attach - Attaches a user-defined buffer for sending.
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Buffer_attach(void *buf, int size)
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_BUFFER_ATTACH(BUF, SIZE, IERROR)
<type> BUF(*)
INTEGER SIZE, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Buffer_attach(buffer, size, ierror)
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buffer
INTEGER, INTENT(IN) :: size
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
C++ Syntax
#include <mpi.h>
void Attach_buffer(void* buffer, int size)
INPUT PARAMETERS
buf Initial buffer address (choice).
size Buffer size, in bytes (integer).
OUTPUT PARAMETER
IERROR Fortran only: Error status (integer).
DESCRIPTION
Provides to MPI a buffer in the user's memory to be used for buffering
outgoing messages. The buffer is used only by messages sent in buffered
mode. Only one buffer can be attached to a process at a time.
NOTES
The size given should be the sum of the sizes of all outstanding Bsends
that you intend to have, plus MPI_BSEND_OVERHEAD bytes for each Bsend
that you do. For the purposes of calculating size, you should use
MPI_Pack_size. In other words, in the code
MPI_Buffer_attach( buf, size );
MPI_Bsend( ..., count=20, datatype=type1, ... );
...
MPI_Bsend( ..., count=40, datatype=type2, ... );
the value of size in the MPI_Buffer_attach call should be greater than
the value computed by
MPI_Pack_size( 20, type1, comm, &s1 );
MPI_Pack_size( 40, type2, comm, &s2 );
size = s1 + s2 + 2 * MPI_BSEND_OVERHEAD;
MPI_BSEND_OVERHEAD gives the maximum amount of buffer space that may be
used by the Bsend routines. This value is in mpi.h for C and mpif.h for
Fortran.
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++ func-
tions 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.
SEE ALSO
MPI_Buffer_detach
4.1.2 Nov 24, 2021 MPI_Buffer_attach(3)
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