NAME

       MPI_Bsend -  Basic send with user-specified buffering

SYNOPSIS

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

INPUT PARAMETERS

       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)

NOTES

       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
       expensive.

NOTES FOR FORTRAN

       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 Fortran.

ERRORS

       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.
       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_COMM
              - Invalid communicator.  A common error is to use a null  communicator  in  a  call
              (not even allowed in MPI_Comm_rank ).
       MPI_ERR_COUNT
              - Invalid count argument.  Count arguments must be non-negative; a count of zero is
              often valid.
       MPI_ERR_TYPE
              -  Invalid  datatype  argument.   May   be   an   uncommitted   MPI_Datatype   (see
              MPI_Type_commit ).
       MPI_ERR_RANK
              -  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 .

       MPI_ERR_TAG
              -  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 .

SEE ALSO

       MPI_Buffer_attach, MPI_Buffer_detach, MPI_Ibsend, MPI_Bsend_init

MORE INFORMATION

       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).

       http://www.mpi-forum.org/

ACKNOWLEDGEMENTS

       The  LAM  Team  would  like the thank the MPICH Team for the handy program to generate man
       pages  ("doctext"  from  ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz  ),  the   initial
       formatting, and some initial text for most of the MPI-1 man pages.

LOCATION

       bsend.c