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MPI_Buffer_attach - Attaches a user-defined buffer for sending.
#include <mpi.h>
int MPI_Buffer_attach(void *buf, int size)
INCLUDE ’mpif.h’
MPI_BUFFER_ATTACH(BUF, SIZE, IERROR)
<type> BUF(*)
INTEGER SIZE, IERROR
#include <mpi.h>
void Attach_buffer(void* buffer, int size)
- buf
- Initial buffer address (choice).
- size
- Buffer size, in
bytes (integer).
- IERROR
- Fortran only: Error status (integer).
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.
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.
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. 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.
MPI_Buffer_detach
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