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NAME

       MPI_Ibsend -  Starts a nonblocking buffered send

SYNOPSIS

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

INPUT PARAMETERS

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

OUTPUT PARAMETER

       preq   - communication request (handle)

NOTES

       It  is  generally  a  bad  idea  to use the MPI_Ibsend 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.

       The communication started with this function is not guaranteed  to  progress  or  complete
       until  req  has been given to one of the test or wait functions ( MPI_Test , MPI_Testall ,
       MPI_Testany , MPI_Testsome , MPI_Wait , MPI_Waitall , MPI_Waitany , MPI_Waitsome ).

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_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 .

       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_BUFFER
              - Invalid buffer pointer.  Usually a null buffer where one is not valid.

SEE ALSO

       MPI_Bsend,   MPI_Test,  MPI_Testall,  MPI_Testany,  MPI_Testsome,  MPI_Wait,  MPI_Waitall,
       MPI_Waitany, MPI_Waitsome

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

       ibsend.c