mpi_bsend(3openmpi) [osx man page]

MPI_Bsend(3OpenMPI)													       MPI_Bsend(3OpenMPI)

NAME

       MPI_Bsend - Basic send with user-specified buffering.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Bsend(void *buf, int count, MPI_Datatype datatype,
	    int dest, int tag, MPI_Comm comm)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_BSEND(BUF, COUNT,DATATYPE, DEST, TAG, COMM, IERROR)
	    <type>    BUF(*)
	    INTEGER   COUNT, DATATYPE, DEST, TAG, COMM, IERROR

C++ Syntax
       #include <mpi.h>
       void Comm::Bsend(const void* buf, int count, const
	    Datatype& datatype, int dest, int tag) const

INPUT PARAMETERS

       buf	 Initial address of send buffer (choice).

       count	 Number of entries in send buffer (nonnegative integer).

       datatype  Datatype of each send buffer element (handle).

       dest	 Rank of destination (integer).

       tag	 Message tag (integer).

       comm	 Communicator (handle).

OUTPUT PARAMETER

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       MPI_Bsend performs a buffered-mode, blocking send.

NOTES

       This  send  is  provided  as  a	convenience  function;	it allows the user to send messages without worrying about where they are buffered
       (because the user must have provided buffer space with MPI_Buffer_attach).

       In deciding how much buffer space to allocate, remember that the buffer space is not available for reuse by  subsequent	MPI_Bsends  unless
       you  are certain that the message has been received (not just that it should have been received).  For example, this code does not allocate
       enough buffer space:

	   MPI_Buffer_attach( b, n*sizeof(double) + MPI_BSEND_OVERHEAD );
	   for (i=0; i<m; i++) {
	       MPI_Bsend( buf, n, MPI_DOUBLE, ... );
	   }

       because only enough buffer space is provided for a single send, and the loop may start a second MPI_Bsend before the first is  done  making
       use of the buffer.

       In C, you can force the messages to be delivered by MPI_Buffer_detach( &b, &n ); MPI_Buffer_attach( b, n ); (The MPI_Buffer_detach will not
       complete until all buffered messages are delivered.)

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_attach
       MPI_Ibsend
       MPI_Bsend_init

Open MPI 1.2							  September 2006					       MPI_Bsend(3OpenMPI)

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MPI_Buffer_attach(3OpenMPI)											       MPI_Buffer_attach(3OpenMPI)

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
       INCLUDE 'mpif.h'
       MPI_BUFFER_ATTACH(BUF, SIZE, IERROR)
	    <type>    BUF(*)
	    INTEGER   SIZE, 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

Open MPI 1.2							  September 2006				       MPI_Buffer_attach(3OpenMPI)

Linux and UNIX Man Pages

mpi_bsend(3openmpi) [osx man page]

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