fixed the residual difference between low and high boundary stencils

Author: shivin9

src/derivative_operators/derivative_operator.jl

@@ -37,8 +37,8 @@ function CenteredDifference{N}(derivative_order::Int,
     _low_boundary_coefs     = SVector{boundary_stencil_length, T}[convert(SVector{boundary_stencil_length, T}, (1/dx^derivative_order) * calculate_weights(derivative_order, oneunit(T)*x0, left_boundary_x)) for x0 in L_boundary_deriv_spots]
     low_boundary_coefs      = convert(SVector{boundary_point_count},_low_boundary_coefs)
 
-    _high_boundary_coefs    = SVector{boundary_stencil_length, T}[convert(SVector{boundary_stencil_length, T}, (1/dx^derivative_order) * calculate_weights(derivative_order, oneunit(T)*x0, reverse(right_boundary_x))) for x0 in R_boundary_deriv_spots]
-    high_boundary_coefs      = convert(SVector{boundary_point_count},reverse(_high_boundary_coefs))
+    # _high_boundary_coefs    = SVector{boundary_stencil_length, T}[convert(SVector{boundary_stencil_length, T}, (1/dx^derivative_order) * calculate_weights(derivative_order, oneunit(T)*x0, reverse(right_boundary_x))) for x0 in R_boundary_deriv_spots]
+    high_boundary_coefs      = convert(SVector{boundary_point_count},reverse(map(reverse, _low_boundary_coefs)))
 
     coefficients            = coeff_func isa Nothing ? nothing : Vector{T}(undef,len)
     DerivativeOperator{T,N,false,T,typeof(stencil_coefs),
@@ -120,7 +120,7 @@ function UpwindDifference{N}(derivative_order::Int,
     stencil_coefs           = convert(SVector{stencil_length, T}, calculate_weights(derivative_order, zero(T), dummy_x))
     _low_boundary_coefs     = SVector{boundary_stencil_length, T}[convert(SVector{boundary_stencil_length, T}, calculate_weights(derivative_order, oneunit(T)*x0, boundary_x)) for x0 in boundary_deriv_spots]
     low_boundary_coefs      = convert(SVector{boundary_point_count},_low_boundary_coefs)
-    high_boundary_coefs     = convert(SVector{boundary_point_count},reverse(SVector{boundary_stencil_length, T}[reverse(low_boundary_coefs[i]) for i in 1:boundary_point_count]))
+    high_boundary_coefs      = convert(SVector{boundary_point_count},reverse(map(reverse, _low_boundary_coefs)))
 
     coefficients            = Vector{T}(undef,len)