MPI_GREQUEST_COMPLETE(3)			     Open MPI				  MPI_GREQUEST_COMPLETE(3)

MPI_Grequest_complete — Reports that a generalized request is complete.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Grequest_complete(MPI_Request request)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'

	  MPI_GREQUEST_COMPLETE(REQUEST, IERROR)
	      INTEGER REQUEST, IERROR

   Fortran 2008 Syntax
	  USE mpi_f08

	  MPI_Grequest_complete(request, ierror)
	      TYPE(MPI_Request), INTENT(IN) :: request
	      INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT/OUTPUT PARAMETER
       • request : Generalized request (handle).

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

DESCRIPTION
       MPI_Grequest_complete  informs  MPI  that the operations represented by the generalized request request are
       complete. A call to MPI_Wait(request,  status)``	 will  return,	and  a	call  to  MPI_Test(request,  flag,
       status)``  will	return	flag=true  only	 after	a  call	 to  MPI_Grequest_complete has declared that these
       operations are complete.

       MPI imposes no restrictions on the code executed	 by  the  callback  functions.	However,  new  nonblocking
       operations  should  be  defined	so  that  the  general	semantic rules about MPI calls such as MPI_Test <#
       mpi-test>, MPI_Request_free <#mpi-request-free>, or MPI_Cancel <#mpi-cancel> still hold. For  example,  all
       these  calls are supposed to be local and nonblocking. Therefore, the callback functions query_fn, free_fn,
       or cancel_fn should invoke blocking MPI communication calls only if the context is such	that  these  calls
       are  guaranteed	to  return  in	finite	time. Once MPI_Cancel <#mpi-cancel> has been invoked, the canceled
       operation should complete in finite time, regardless of the state of other  processes  (the  operation  has
       acquired	 “local”  semantics).  It  should  either  succeed  or	fail without side-effects. The user should
       guarantee these same properties for newly defined operations.

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.

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				  MPI_GREQUEST_COMPLETE(3)
