MPI_Sendrecv_replace(3) Open MPI MPI_Sendrecv_replace(3)NAMEMPI_Sendrecv_replace - Sends and receives a message using a single buf‐
fer.
SYNTAXC Syntax
#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)
Fortran Syntax
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
C++ Syntax
#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
INPUT/OUTPUT PARAMETER
buf Initial address of send and receive buffer (choice).
INPUT PARAMETERS
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).
OUTPUT PARAMETERS
status Status object (status).
IERROR Fortran only: Error status (integer).
DESCRIPTION
The send-receive operations combine in one call the sending of a mes‐
sage 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 opera‐
tion 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 pro‐
cesses receive first, then send) in order to prevent cyclic dependen‐
cies 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 opera‐
tion 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 mes‐
sage 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.
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_Sendrecv
1.7.4 Feb 04, 2014 MPI_Sendrecv_replace(3)
