s_bsplines_non_uniform__init Subroutine

  subroutine s_bsplines_non_uniform__init( self, degree, periodic, breaks )
    class(sll_t_bsplines_non_uniform), intent(  out) :: self
    integer                          , intent(in   ) :: degree
    logical                          , intent(in   ) :: periodic
    real(wp)                         , intent(in   ) :: breaks(:)

    integer  :: i
    real(wp) :: period ! length of period for periodic B-splines

    ! Public attributes
    self % degree   = degree
    self % periodic = periodic
    self % uniform  = .false.
    self % ncells   = size(breaks) - 1
    self % nbasis   = merge( self%ncells, self%ncells+degree, periodic )
    self % offset   = merge( degree/2   , 0                 , periodic )
    self % xmin     = breaks(1)
    self % xmax     = breaks(self%ncells+1)

    ! Create the knots array from the grid points. Here take the grid points
    ! as knots and simply add to the left and the right the
    ! amount of knots that depends on the degree of the requested
    ! spline. We aim at setting up the indexing in such a way that the
    ! original indexing of 'grid' is preserved, i.e.: grid(i) = knot(i), at
    ! least whenever the scope of the indices defined here is active.
    associate( npoints => self%ncells+1 )

      allocate( self % knots(1-degree:npoints+degree) )

      do i = 1, npoints
        self%knots(i) = breaks(i)
      end do

      ! Fill out the extra nodes
      if ( periodic ) then
        period = breaks(npoints) - breaks(1)
        do i = 1, degree
          self%knots(1-i)       = breaks(npoints-i) - period
          self%knots(npoints+i) = breaks(i+1)       + period
        end do
      else ! open
        do i = 1, degree
          self%knots(1-i)       = breaks(1)
          self%knots(npoints+i) = breaks(npoints)
        end do
      end if

    end associate

  end subroutine s_bsplines_non_uniform__init