MPI_TESTANY(3)					     Open MPI					    MPI_TESTANY(3)

MPI_Testany — Tests for completion of any one previously initiated communication in a list.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Testany(int count, MPI_Request array_of_requests[],
	       int *index, int *flag, MPI_Status *status)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_TESTANY(COUNT, ARRAY_OF_REQUESTS, INDEX, FLAG, STATUS, IERROR)
	       LOGICAL FLAG
	       INTEGER COUNT, ARRAY_OF_REQUESTS(*), INDEX
	       INTEGER STATUS(MPI_STATUS_SIZE), IERROR

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Testany(count, array_of_requests, index, flag, status, ierror)
	       INTEGER, INTENT(IN) :: count
	       TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(count)
	       INTEGER, INTENT(OUT) :: index
	       LOGICAL, INTENT(OUT) :: flag
	       TYPE(MPI_Status) :: status
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • count: List length (integer).

       • array_of_requests: Array of requests (array of handles).

OUTPUT PARAMETERS
       • index: Index of operation that completed, or MPI_UNDEFINED if none completed (integer).

       • flag: True if one of the operations is complete (logical).

       • status: Status object (status).

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

DESCRIPTION
       MPI_Testany tests for completion of either one or none of the operations associated with active handles. In
       the  former  case,  it  returns	flag  = true, returns in index the index of this request in the array, and
       returns in status the status of that operation; if the request was allocated by a nonblocking communication
       call then the request is deallocated and the handle is set to MPI_REQUEST_NULL. (The array is indexed  from
       0  in  C,  and  from  1	in Fortran.) In the latter case (no operation completed), it returns flag = false,
       returns a value of MPI_UNDEFINED in index, and status is undefined.

       The array may contain null or inactive handles. If the array contains  no  active  handles  then	 the  call
       returns immediately with flag = true, index = MPI_UNDEFINED, and an empty status.

       If   the	  array	  of   requests	  contains   active  handles  then  the	 execution  of	MPI_Testany(count,
       array_of_requests, index, status) has the same effect as the execution  of  MPI_Test(&array_of_requests[i],
       flag,  status),	for  i=0,1,…,count-1,  in some arbitrary order, until one call returns flag = true, or all
       fail. In the former case, index is set to the last value of i, and  in  the  latter  case,  it  is  set	to
       MPI_UNDEFINED. MPI_Testany with an array containing one active entry is equivalent to MPI_Test <#mpi-test>.

       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  requests	passed	to  MPI_Testany	 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_Testany 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_Comm_set_errhandler <#mpi-comm-set-errhandler>

	  • MPI_File_set_errhandler <#mpi-file-set-errhandler>

	  • MPI_Test <#mpi-test>

	  • MPI_Testall <#mpi-testall>

	  • MPI_Testsome <#mpi-testsome>

	  • MPI_Wait <#mpi-wait>

	  • MPI_Waitall <#mpi-waitall>

	  • MPI_Waitany <#mpi-waitany>

	  • MPI_Waitsome <#mpi-waitsome>

	  • MPI_Win_set_errhandler <#mpi-win-set-errhandler>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					    MPI_TESTANY(3)
