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       MPI_Bsend -  Basic send with user-specified buffering


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


       buf    - initial address of send buffer (choice)
       count  - number of elements in send buffer (nonnegative integer)
       dtype  - datatype of each send buffer element (handle)
       dest   - rank of destination (integer)
       tag    - message tag (integer)
       comm   - communicator (handle)


       This  send is provided as a convenience function; it allows the user to
       send messages without worring 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_Bsend s  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.)

       It is generally a bad  idea  to  use  the  MPI_Bsend  function,  as  it
       guarantees  that  the  entire  message  will  suffer the overhead of an
       additional memory copy.  For large  messages,  or  when  shared  memory
       message   transports  are  being  used,  this  overhead  can  be  quite


       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK )  have
       an  additional  argument ierr at the end of the argument list.  ierr is
       an integer and has the same meaning as the return value of the  routine
       in  C.   In Fortran, MPI routines are subroutines, and are invoked with
       the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in


       If an error occurs in an MPI function, the current MPI error handler is
       called to handle it.  By default, this error  handler  aborts  the  MPI
       job.   The  error  handler may be changed with MPI_Errhandler_set ; the
       predefined error handler MPI_ERRORS_RETURN may be used to  cause  error
       values  to  be  returned  (in C and Fortran; this error handler is less
       useful in with the C++ MPI  bindings.   The  predefined  error  handler
       MPI::ERRORS_THROW_EXCEPTIONS  should  be used in C++ if the error value
       needs to be recovered).  Note that MPI does not guarantee that  an  MPI
       program can continue past an error.

       All  MPI  routines  (except  MPI_Wtime  and MPI_Wtick ) return an error
       value; C routines as the value of the function and Fortran routines  in
       the  last  argument.   The  C++  bindings  for  MPI do not return error
       values; instead, error values are communicated by  throwing  exceptions
       of  type  MPI::Exception  (but  not  by  default).  Exceptions are only
       thrown if the error value is not MPI::SUCCESS .

       Note that if the MPI::ERRORS_RETURN handler is set in  C++,  while  MPI
       functions  will  return  upon an error, there will be no way to recover
       what the actual error value was.
              - No error; MPI routine completed successfully.
              - Invalid communicator.   A  common  error  is  to  use  a  null
              communicator in a call (not even allowed in MPI_Comm_rank ).
              - Invalid count argument.  Count arguments must be non-negative;
              a count of zero is often valid.
              - Invalid datatype argument.  May be an uncommitted MPI_Datatype
              (see MPI_Type_commit ).
              -  Invalid  source  or  destination rank.  Ranks must be between
              zero and the size of the communicator  minus  one;  ranks  in  a
              receive  (  MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
              be MPI_ANY_SOURCE .

              - Invalid tag argument.  Tags must be non-negative;  tags  in  a
              receive  ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.)  may also
              be MPI_ANY_TAG .  The largest tag value is available through the
              the attribute MPI_TAG_UB .


       MPI_Buffer_attach, MPI_Buffer_detach, MPI_Ibsend, MPI_Bsend_init


       For more information, please see the official MPI Forum web site, which
       contains the text  of  both  the  MPI-1  and  MPI-2  standards.   These
       documents contain detailed information about each MPI function (most of
       which is not duplicated in these man pages).


       The LAM Team would like the thank the MPICH Team for the handy  program
       to        generate        man        pages        ("doctext"       from    ),    the     initial
       formatting, and some initial text for most of the MPI-1 man pages.