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MPI_Bsend - Basic send with user-specified buffering.
#include <mpi.h>
int MPI_Bsend(void *buf, int count, MPI_Datatype datatype,
int dest, int tag, MPI_Comm comm)
INCLUDE ’mpif.h’
MPI_BSEND(BUF, COUNT,DATATYPE, DEST, TAG, COMM, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, DEST, TAG, COMM, IERROR
#include <mpi.h>
void Comm::Bsend(const void* buf, int count, const
Datatype& datatype, int dest, int tag) const
- 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
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