MPI_Bsend(3) MPI MPI_Bsend(3)NAMEMPI_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 com‐
municators), 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 prede‐
fined 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 commu‐
nicator 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
8/22/2013 MPI_Bsend(3)
