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MPI_Sendrecv - Sends and receives a message.
#include <mpi.h>
int MPI_Sendrecv(const 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)
USE MPI
! or the older form: 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
USE mpi_f08
MPI_Sendrecv(sendbuf, sendcount, sendtype, dest, sendtag, recvbuf,
recvcount, recvtype, source, recvtag, comm, status, ierror)
TYPE(*), DIMENSION(..), INTENT(IN) :: sendbuf
TYPE(*), DIMENSION(..) :: recvbuf
INTEGER, INTENT(IN) :: sendcount, dest, sendtag, recvcount, source,
recvtag
TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
TYPE(MPI_Comm), INTENT(IN) :: comm
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- 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).
- recvbuf
- Initial address of receive buffer (choice).
- status
- Status object (status).
This refers to the receive operation.
- 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-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.
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_replace
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