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MPI_Sendrecv_replace - Sends and receives a message using a single
buffer.
#include <mpi.h>
int MPI_Sendrecv_replace(void *buf, int count, MPI_Datatype datatype,
int dest, int sendtag, int source, int recvtag, MPI_Comm comm,
MPI_Status *status)
INCLUDE ’mpif.h’
MPI_SENDRECV_REPLACE(BUF, COUNT, DATATYPE, DEST, SENDTAG, SOURCE,
RECVTAG, COMM, STATUS, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, DEST, SENDTAG
INTEGER SOURCE, RECVTAG, COMM
INTEGER STATUS(MPI_STATUS_SIZE), IERROR
#include <mpi.h>
void Comm::Sendrecv_replace(void* buf, int count, const
Datatype& datatype, int dest, int sendtag, int source,
int recvtag, Status& status) const
void Comm::Sendrecv_replace(void* buf, int count, const
Datatype& datatype, int dest, int sendtag, int source,
int recvtag) const
- buf
- Initial address of send and receive buffer (choice).
- count
- Number of elements in send and receive buffer (integer).
- datatype
- Type of elements to send and receive (handle).
- dest
- Rank of destination
(integer).
- sendtag
- Send message tag (integer).
- source
- Rank of source (integer).
- recvtag
- Receive message tag (integer).
- comm
- Communicator (handle).
- status
- Status object (status).
- IERROR
- Fortran only: Error status
(integer).
The send-receive operations combine in one call the
sending of a message to one destination and the receiving of another message,
from another process. The two (source and destination) are possibly the
same. A send-receive operation is useful for executing a shift operation
across a chain of processes. If blocking sends and receives are used for
such a shift, then one needs to order the sends and receives correctly
(for example, even processes send, then receive; odd processes receive
first, then send) in order to prevent cyclic dependencies that may lead
to deadlock. When a send-receive operation is used, the communication subsystem
takes care of these issues. The send-receive operation can be used in conjunction
with the functions described in Chapter 6 of the MPI Standard, "Process
Topologies," in order to perform shifts on various logical topologies. Also,
a send-receive operation is useful for implementing remote procedure calls.
A message sent by a send-receive operation can be received by a regular
receive operation or probed by a probe operation; a send-receive operation
can receive a message sent by a regular send operation.
MPI_Sendrecv_replace
executes a blocking send and receive. The same buffer is used both for the
send and for the receive, so that the message sent is replaced by the message
received.
The semantics of a send-receive operation is what would be obtained
if the caller forked two concurrent threads, one to execute the send, and
one to execute the receive, followed by a join of these two threads.
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_Sendrecv
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