MPI_MRECV(3)					     Open MPI					      MPI_MRECV(3)

MPI_Mrecv — Blocking receive for a matched message

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Mrecv(void *buf, int count, MPI_Datatype type,
	       MPI_Message *message, MPI_Status *status)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_MRECV(BUF, COUNT, DATATYPE, MESSAGE, STATUS, IERROR)
	       <type>  BUF(*)
	       INTEGER COUNT, DATATYPE, MESSAGE
	       INTEGER STATUS(MPI_STATUS_SIZE), IERROR

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Mrecv(buf, count, datatype, message, status, ierror)
	       TYPE(*), DIMENSION(..) :: buf
	       INTEGER, INTENT(IN) :: count
	       TYPE(MPI_Datatype), INTENT(IN) :: datatype
	       TYPE(MPI_Message), INTENT(INOUT) :: message
	       TYPE(MPI_Status) :: status
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • count: Number of elements to receive (nonnegative integer).

       • datatype: Datatype of each send buffer element (handle).

       • message: Message (handle).

OUTPUT PARAMETERS
       • buf: Initial address of receive buffer (choice).

       • status: Status object (status).

       • ierror: Fortran only: Error status (integer).

DESCRIPTION
       The  functions MPI_Mrecv and MPI_Imrecv <#mpi-imrecv> receive messages that have been previously matched by
       a matching probe.

       If MPI_Mrecv is called with MPI_MESSAGE_NULL as the message argument, the call returns immediately with the
       status object set to source = MPI_PROC_NULL, tag = MPI_ANY_TAG, and  count  =  0,  as  if  a  receive  from
       MPI_PROC_NULL was issued.

       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_Mrecv	 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_Mrecv 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_Mprobe <#mpi-mprobe>

	  • MPI_Improbe <#mpi-improbe>

	  • MPI_Probe <#mpi-probe>

	  • MPI_Iprobe <#mpi-iprobe>

	  • MPI_Imrecv <#mpi-imrecv>

	  • MPI_Cancel <#mpi-cancel>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					      MPI_MRECV(3)
