2.3 KiB
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
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.
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.