DragonFly On-Line Manual Pages

Search: Section:  

MPI_Bsend(3)                          MPI                         MPI_Bsend(3)


NAME

       MPI_Bsend -  Basic send with user-provided buffering


SYNOPSIS

       int MPI_Bsend(MPICH2_CONST void *buf, int count, MPI_Datatype datatype, 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)
       datatype
              - 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.)


THREAD AND INTERRUPT SAFETY

       This routine is thread-safe.  This means that this routine may be
       safely used by multiple threads without the need for any user-provided
       thread locks.  However, the routine is not interrupt safe.  Typically,
       this is due to the use of memory allocation routines such as malloc or
       other non-MPICH runtime routines that are themselves not interrupt-
       safe.


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

       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.  Before the value is returned, the current MPI error
       handler is called.  By default, this error handler aborts the MPI job.
       The error handler may be changed with MPI_Comm_set_errhandler (for
       communicators), MPI_File_set_errhandler (for files), and
       MPI_Win_set_errhandler (for RMA windows).  The MPI-1 routine
       MPI_Errhandler_set may be used but its use is deprecated.  The
       predefined error handler MPI_ERRORS_RETURN may be used to cause error
       values to be returned.  Note that MPI does not guarentee that an MPI
       program can continue past an error; however, MPI implementations will
       attempt to continue whenever possible.

       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_Ibsend, MPI_Bsend_init


LOCATION

       src/mpi/pt2pt/bsend.c

                                   9/20/2012                      MPI_Bsend(3)

Search: Section: