MPI_GROUP_FROM_SESSION_PSET(3)			     Open MPI			    MPI_GROUP_FROM_SESSION_PSET(3)

MPI_Group_from_session_pset — Creates a group using a provided session handle and process set.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Group_from_session_pset(MPI_Session session, const char *pset_name, MPI_Group *newgroup)

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

	  MPI_GROUP_FROM_SESSION_PSET(SESSION, PSET_NAME, NEWGROUP, IERROR)
	      INTEGER SESSION,	NEWGROUP, IERROR
	      CHARACTER*(*) PSET_NAME

   Fortran 2008 Syntax
	  USE mpi_f08

	  MPI_Group_from_session_pset(session, pset_name, newgroup, ierror)
	      TYPE(MPI_Session), INTENT(IN) :: session
	      CHARACTER(LEN=*), INTENT(IN) :: pset_name
	      TYPE(MPI_Group), INTENT(OUT) :: newgroup
	      INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • session : Session (handle).

       •

	 pset_name (name of process set to use to create the new group)
		(string)

OUTPUT PARAMETERS
       •

	 newgroup (New group derived from supplied session and process set)
		(handle).

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

DESCRIPTION
       The  function  MPI_Group_from_session_pset  creates  a group newgroup using the provided session handle and
       process set. The process set name must be one returned from an invocation  of  MPI_Session_get_nth_pset	<#
       mpi-session-get-nth-pset>   using   the	 supplied  session  handle.  If	 the  pset_name	 does  not  exist,
       MPI_GROUP_NULL will be returned in the newgroup argument.

NOTE
       As with other group constructors, MPI_Group_from_session_pset is a local function.

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_Session_init <#mpi-session-init>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026			    MPI_GROUP_FROM_SESSION_PSET(3)
