comments

Author: vpuri3

src/fft.jl

@@ -1085,6 +1085,7 @@ function _mul(p::AdjointPlan{T}, x::AbstractArray, PS::R2RProjectionStyle) where
     dims = fftdims(p)
 
     N = 1
+    # Ref: https://www.fftw.org/fftw3_doc/1d-Real_002deven-DFTs-_0028DCTs_0029.html
     # Normalization: P \ P * u = K * u
     # 0, 1 , 2   : NoProjectionStyle() type: K = prod(size(N))
     # 3, 6 : DCTs: K = 2 * (N - 1)

test/runtests.jl

@@ -583,6 +583,8 @@ end
         y = randn(size(x))
         N = ndims(x)
         for dims in unique((1, 1:N, N))
+
+            # DCT/ IDCT
             for P in (plan_dct(x, dims), plan_idct(x, dims))
                 @test (P')' * x == P * x
                 @test size(P') == AbstractFFTs.output_size(P)