g1_parabolic Function

    pure function g1_parabolic(r) result(val)
      ! Parabolic filter.
      implicit none
      real(wp), intent(in) :: r                                                !! Distance from filter center
      real(wp)             :: val                                              !! Result

      if ( (abs(r).le. 1.0_wp)) then
        val=3.0_wp/4.0_wp*(1.0_wp-abs(r)**2)
      else
        val=0.0_WP
      end if

      return
    end function g1_parabolic