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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++ 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




Open MPI 1.2                                   September 2006                            MPI_Bsend(3OpenMPI)