MPI_Bsend(3) Open MPI MPI_Bsend(3)
NAME
MPI_Bsend - Basic send with user-specified buffering.
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Bsend(const void *buf, int count, MPI_Datatype datatype,
int dest, int tag, MPI_Comm comm)
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_BSEND(BUF, COUNT,DATATYPE, DEST, TAG, COMM, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, DEST, TAG, COMM, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Bsend(buf, count, datatype, dest, tag, comm, ierror)
TYPE(*), DIMENSION(..), INTENT(IN) :: buf
INTEGER, INTENT(IN) :: count, dest, tag
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Comm), INTENT(IN) :: comm
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
C++ Syntax
#include <mpi.h>
void Comm::Bsend(const void* buf, int count, const
Datatype& datatype, int dest, int tag) const
INPUT PARAMETERS
buf Initial address of send buffer (choice).
count Number of entries 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).
OUTPUT PARAMETER
IERROR Fortran only: Error status (integer).
DESCRIPTION
MPI_Bsend performs a buffered-mode, blocking send.
NOTES
This send is provided as a convenience function; it allows the user to
send messages without worrying 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_Bsends 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.)
ERRORS
Almost all MPI routines return an error value; C routines as the value
of the function and Fortran routines in the last argument. C++ func-
tions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
may be used to cause error values to be returned. Note that MPI does
not guarantee that an MPI program can continue past an error.
SEE ALSO
MPI_Buffer_attach
MPI_Ibsend
MPI_Bsend_init
4.1.2 Nov 24, 2021 MPI_Bsend(3)
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