MPI_QUERY_THREAD(3)				     Open MPI				       MPI_QUERY_THREAD(3)

MPI_Query_thread — Returns the current level of thread support

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Query_thread(int *provided)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_QUERY_THREAD(PROVIDED, IERROR)
	       INTEGER PROVIDED, IERROR

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Query_thread(provided, ierror)
	       INTEGER, INTENT(OUT) :: provided
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

OUTPUT PARAMETERS
       • provided: C/Fortran only: Level of thread support (integer).

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

DESCRIPTION
       This  routine returns in provided the current level of thread support.  If MPI was initialized by a call to
       MPI_Init_thread <#mpi-init-thread>, provided will have the same value as was returned by that function.

       The possible values of provided are as follows:

       MPI_THREAD_SINGLE
	      Only one thread may execute.

       MPI_THREAD_FUNNELED
	      If the process is multithreaded, only the thread that called MPI_Init[_thread] may make MPI calls.

       MPI_THREAD_SERIALIZED
	      If the process is multithreaded, only one thread may make MPI library calls at one time.

       MPI_THREAD_MULTIPLE
	      If the process is multithreaded, multiple threads may call MPI at once with no restrictions.

NOTES
       In Open	MPI,  provided	is  always  MPI_THREAD_SINGLE,	unless	the  program  has  been	 linked	 with  the
       multithreaded library, in which case provided is MPI_THREAD_MULTIPLE.

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.

       See also:

	  • MPI_Init <#mpi-init>

	  • MPI_Init_thread <#mpi-init-thread>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				       MPI_QUERY_THREAD(3)
