NAME

       MPI_Bsend - Basic send with user-specified buffering.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Bsend(const 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