MPI_Bsend − Basic send with user-specified buffering.
#include
<mpi.h>
int MPI_Bsend(const void *buf, int count,
MPI_Datatype datatype,
int dest, int tag, MPI_Comm comm) |
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 |
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 |
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). |
IERROR |
Fortran only: Error status (integer). |
MPI_Bsend performs a buffered-mode, blocking send.
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.)
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions 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.
MPI_Buffer_attach
MPI_Ibsend
MPI_Bsend_init