MPI_Bsend(3)                       Open MPI                       MPI_Bsend(3)



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++
       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.


SEE ALSO
       MPI_Buffer_attach
       MPI_Ibsend
       MPI_Bsend_init




1.4.1                            Jan 14, 2010                     MPI_Bsend(3)
