Ubuntu Manpage: MPI_Bsend - Basic send with user-provided buffering

NAME

       MPI_Bsend -  Basic send with user-provided buffering

SYNOPSIS

       int MPI_Bsend(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. Additionally, this error can occur if an uncommitted
MPI_Datatype (see MPI_Type_commit ) is used in a communication call.
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 .