MPI_Sendrecv(3OpenMPI)													    MPI_Sendrecv(3OpenMPI)

NAME

       MPI_Sendrecv - Sends and receives a message.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Sendrecv(void *sendbuf, int sendcount, MPI_Datatype sendtype,
	    int dest, int sendtag, void *recvbuf, int recvcount,
	    MPI_Datatype recvtype, int source, int recvtag,
	    MPI_Comm comm, MPI_Status *status)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_SENDRECV(SENDBUF, SENDCOUNT, SENDTYPE, DEST, SENDTAG,
		 RECVBUF, RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM,
		 STATUS, IERROR)
	    <type>    SENDBUF(*), RECVBUF(*)
	    INTEGER   SENDCOUNT, SENDTYPE, DEST, SENDTAG
	    INTEGER   RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM
	    INTEGER   STATUS(MPI_STATUS_SIZE), IERROR

C++ Syntax
       #include <mpi.h>
       void Comm::Sendrecv(const void *sendbuf, int sendcount, const
	    Datatype& sendtype, int dest, int sendtag, void *recvbuf,
	    int recvcount, const Datatype& recvtype, int source,
	    int recvtag, Status& status) const

       void Comm::Sendrecv(const void *sendbuf, int sendcount, const
	    Datatype& sendtype, int dest, int sendtag, void *recvbuf,
	    int recvcount, const Datatype& recvtype, int source,
	    int recvtag) const

INPUT PARAMETERS

       sendbuf	 Initial address of send buffer (choice).

       sendcount Number of elements to send (integer).

       sendtype  Type of elements in send buffer (handle).

       dest	 Rank of destination (integer).

       sendtag	 Send tag (integer).

       recvcount Maximum number of elements to receive (integer).

       recvtype  Type of elements in receive buffer (handle).

       source	 Rank of source (integer).

       recvtag	 Receive tag (integer).

       comm	 Communicator (handle).

OUTPUT PARAMETERS

       recvbuf	 Initial address of receive buffer (choice).

       status	 Status object (status). This refers to the receive operation.

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       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 cor-
       rectly (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-1 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 executes a blocking send and receive operation. Both send and receive use the same communicator, but possibly different  tags.
       The send buffer and receive buffers must be disjoint, and may have different lengths and datatypes.

       If your application does not need to examine the status field, you can save resources by using the predefined constant MPI_STATUS_IGNORE as
       a special value for the status argument.

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_replace

Open MPI 1.2							  September 2006					    MPI_Sendrecv(3OpenMPI)