tem_init_tracker_subTree Subroutine

  subroutine tem_init_tracker_subTree( me, tree, solver, bc_prop, stencil, &
    &                                  prefix )
    ! -------------------------------------------------------------------- !
    !> tracking entities
    type(tem_tracking_type), intent(inout)             :: me
    !> Global mesh from which the elements are identified and then stored to
    !! sub-meshes inside the trackers
    type(treelmesh_type), intent(in)                   :: tree
    !> bc property that used to identify elements of certain BCs
    type( tem_bc_prop_type ), intent(in)               :: bc_prop
    !> Global solver information
    type(tem_solveHead_type), intent(in)               :: solver
    !> stencil used to create subTree of boundary type
    type(tem_stencilHeader_type), optional, intent(in) :: stencil
    !> Prefix for output filename
    !! Usually: solver%simName
    character(len=labelLen), optional, intent(in)      :: prefix
    ! -------------------------------------------------------------------- !
    integer :: iLog, nActive
    ! temporary tracker array
    type( tem_tracking_instance_type ), allocatable :: tempTrack(:)
    ! prefix for tracking label
    character(len=pathLen) :: prefix_loc
    ! tracking%config%prefix//tracking%config%label
    character(len=pathLen) :: basename
    ! -------------------------------------------------------------------- !
    call tem_horizontalSpacer(fUnit=logUnit(1))
    write(logUnit(3),*) 'Initialize tracking subTree to remove empty objects'
    call tem_horizontalSpacer(fUnit=logUnit(1))

    nActive = 0

    if (present(prefix)) then
      prefix_loc = trim(prefix)
    else
      ! prefix for tracking label
      prefix_loc = trim(solver%simName)//'_'
    end if

    if( me%control%active ) then
      ! Allocate the temporary track
      allocate(tempTrack( me%control%nDefined ) )

      do iLog = 1, me%control%nDefined

        basename = trim(me%config(iLog)%prefix) // trim(prefix_loc) // &
          &        trim(me%config(iLog)%label)

        write(logUnit(3),*) 'Creating subTree for tracking object ' &
          &                 // trim( me%config(iLog)%label )

        !-----------------------------------------------------------------------
        ! identify tracker elements
        !-----------------------------------------------------------------------
        call tem_create_subTree_of( inTree    = tree,                       &
          &                         bc_prop   = bc_prop,                    &
          &                         stencil   = stencil,                    &
          &                         subTree   = me%instance(iLog)%subTree,  &
          &                         inShape   = me%config(iLog)%geometry,   &
          &                         storePnts = me%config(iLog)             &
          &                                     %output_config%useGetPoint, &
          &                         prefix    = trim(basename)              )

        ! get rid of the empty track in order to avoid empty writes to disk
        if ( me%instance(iLog)%subTree%useGlobalMesh .or. &
          &  ( me%instance(iLog)%subTree%nElems > 0 ) .or. &
          &  ( me%instance(iLog)%subTree%nPoints > 0) ) then
          nActive = nActive + 1
          tempTrack( nActive ) = me%instance(iLog)
          ! Pointer to array of tracking headers loaded from config file
          tempTrack( nActive )%pntConfig = iLog
        end if

      end do  ! nActive

      deallocate(me%instance)
      allocate( me%instance(nActive) )
      me%control%nActive = nActive

      do iLog = 1, nActive
        ! Copy the stuff from the temporary track
        me%instance(iLog) = temptrack(iLog)
      end do

      deallocate(temptrack)
    end if ! if tracking active

  end subroutine tem_init_tracker_subTree