SYNTAX

   C Syntax
          #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)

   Fortran Syntax
          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

   Fortran 2008 Syntax
          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

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
       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 the “Process Topologies” chapter in the MPI Standard 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 return result of the function and
       Fortran routines in the last argument.

       Before the error value is returned, the current MPI  error  handler  associated  with  the  communication
       object  (e.g.,  communicator, window, file) is called.  If no communication object is associated with the
       MPI call, then the call is considered attached to MPI_COMM_SELF and will call the  associated  MPI  error
       handler.   When   MPI_COMM_SELF   is   not  initialized  (i.e.,  before  MPI_Init/MPI_Init_thread,  after
       MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial  error  handler.
       The  initial  error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using
       the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info  key  to  MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.   If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
       error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is  called  for  all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called  on  a  communicator,  it  acts  as if MPI_Abort was called on that communicator. If called on a
         window or file, acts as if MPI_Abort was called on a communicator containing the group of processes  in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       Note  that  per  the  “Return  Status”  section  in the “Point-to-Point Communication” chapter in the MPI
       Standard, MPI errors on messages received by MPI_Sendrecv do not set the status.MPI_ERROR  field  in  the
       returned status.  The error code is always passed to the back-end error handler and may be passed back to
       the  caller  through  the  return  value  of  MPI_Sendrecv if the back-end error handler returns it.  The
       pre-defined MPI error handler MPI_ERRORS_RETURN exhibits this behavior, for example.

       SEE ALSO:

          • MPI_Sendrecv_replace

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                                   MPI_SENDRECV(3)