MPI_SENDRECV(3)					     Open MPI					   MPI_SENDRECV(3)

MPI_Sendrecv — Sends and receives a message.

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 <https://www.mpi-forum.org/
       docs/> 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>/MPI_Init_thread <#mpi-init-thread>,
       after MPI_Finalize <#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 <#
       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>/MPI_Comm_spawn_multiple	<#
       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 <#mpi-abort> was called on that communicator. If called
	 on  a window or file, acts as if MPI_Abort <#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	<#mpi-comm-create-errhandler>	  then	   MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	 <#mpi-file-create-errhandler>	   then	    MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

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

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       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
       <https://www.mpi-forum.org/docs/>, 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 <#mpi-sendrecv-replace>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					   MPI_SENDRECV(3)
