Adding tests, fixing minor issues.

- Fixed an issue where the DCT/DST parameters weren't passed in the right order
- Fixed an issue where the norm factor of the DCT wasn't computed correctly (incorrect delta)
- Generated a unit_fft file that tests various parameters of FFT. Values are generated using scipy.fft module for the FFT, DCT and DST functions
- Changed pocketfft::detail:: namespace usage to just pocketfft:: in the C++ code for more readability

src/owl/fftpack/owl_fft_generic.mli

@@ -85,7 +85,7 @@ val dct
   -> ('a, 'b) t
   -> ('a, 'b) t
 (** [dct ?axis ?ttype ?norm ?ortho ?nthreads x] performs 1-dimensional Discrete Cosine Transform (DCT) on a real input.
-    [ttype] is the DCT type to use for this transform. Default value is [II].
+    [ttype] is the DCT type to use for this transform. Default value is [Two].
     [norm] is the normalization option. By default, [norm] is set to [Backward].
     [ortho] constrols whether or not we should use the orthogonalized variant of the DCT. *)
 
@@ -98,7 +98,7 @@ val idct
   -> ('a, 'b) t
   -> ('a, 'b) t
 (** [idct ?axis ?ttype ?norm ?ortho ?nthreads x] performs inverse 1-dimensional Discrete Cosine Transform (DCT) on a real input.
-    [ttype] is the DCT type to use for this transform. Default value is [II].
+    [ttype] is the DCT type to use for this transform. Default value is [Two].
     [norm] is the normalization option. By default, [norm] is set to [Forward].
     [ortho] constrols whether or not we should use the orthogonalized variant of the DCT. *)
 
@@ -111,7 +111,7 @@ val dst
   -> ('a, 'b) t
   -> ('a, 'b) t
 (** [dst ?axis ?ttype ?norm ?ortho ?nthreads x] performs 1-dimensional Discrete Sine Transform (DCT) on a real input.
-    [ttype] is the DCT type to use for this transform. Default value is [II].
+    [ttype] is the DCT type to use for this transform. Default value is [Two].
     [norm] is the normalization option. By default, [norm] is set to [Backward].
     [ortho] constrols whether or not we should use the orthogonalized variant of the DST. *)
 
@@ -124,6 +124,6 @@ val idst
   -> ('a, 'b) t
   -> ('a, 'b) t
 (** [idst ?axis ?ttype ?norm ?ortho ?nthreads x] performs inverse 1-dimensional Discrete Sine Transform (DST) on a real input.
-    [ttype] is the DST type to use for this transform. Default value is [II].
+    [ttype] is the DST type to use for this transform. Default value is [Two].
     [norm] is the normalization option. By default, [norm] is set to [Forward].
     [ortho] constrols whether or not we should use the orthogonalized variant of the DST. *)

src/owl/fftpack/owl_fftpack.ml

@@ -181,10 +181,10 @@ let _owl_dctb
     -> int
     -> unit
   =
-  fun ityp x y ttype axis norm ortho nthreads ->
+  fun ityp x y axis ttype norm ortho nthreads ->
   match ityp with
-  | Float32 -> owl_float32_dct x y (inverse_map ttype) axis norm ortho nthreads
-  | Float64 -> owl_float64_dct x y (inverse_map ttype) axis norm ortho nthreads
+  | Float32 -> owl_float32_dct x y axis (inverse_map ttype) norm ortho nthreads
+  | Float64 -> owl_float64_dct x y axis (inverse_map ttype) norm ortho nthreads
   | _ -> failwith "_owl_dctb: unsupported operation"
 
 
@@ -241,8 +241,8 @@ let _owl_dstb
     -> int
     -> unit
   =
-  fun ityp x y ttype axis norm ortho nthreads ->
+  fun ityp x y axis ttype norm ortho nthreads ->
   match ityp with
-  | Float32 -> owl_float32_dst x y (inverse_map ttype) axis norm ortho nthreads
-  | Float64 -> owl_float64_dst x y (inverse_map ttype) axis norm ortho nthreads
+  | Float32 -> owl_float32_dst x y axis (inverse_map ttype) norm ortho nthreads
+  | Float64 -> owl_float64_dst x y axis (inverse_map ttype) norm ortho nthreads
   | _ -> failwith "_owl_dstb: unsupported operation"

src/owl/fftpack/owl_fftpack_impl.h

@@ -93,8 +93,8 @@ extern "C"
       Treal norm_factor = compute_norm_factor<Treal>(dims, axes, norm);
       try
       {
-        pocketfft::detail::c2c(dims, stride_in, stride_out, axes, forward,
-                               X_data, Y_data, norm_factor, nthreads);
+        pocketfft::c2c(dims, stride_in, stride_out, axes, forward,
+                       X_data, Y_data, norm_factor, nthreads);
       }
       catch (const std::exception &e)
       {
@@ -294,12 +294,12 @@ extern "C"
 
     shape_t axes{static_cast<size_t>(d)};
     {
-      Treal norm_factor = (type == 1) ? compute_norm_factor<Treal>(dims, axes, norm, 2, 1)
+      Treal norm_factor = (type == 1) ? compute_norm_factor<Treal>(dims, axes, norm, 2, -1)
                                       : compute_norm_factor<Treal>(dims, axes, norm, 2);
       try
       {
-        pocketfft::detail::dct(dims, stride_in, stride_out, axes, type,
-                               X_data, Y_data, norm_factor, ortho, nthreads);
+        pocketfft::dct(dims, stride_in, stride_out, axes, type,
+                       X_data, Y_data, norm_factor, ortho, nthreads);
       }
       catch (const std::exception &e)
       {
@@ -364,8 +364,8 @@ extern "C"
                                       : compute_norm_factor<Treal>(dims, axes, norm, 2);
       try
       {
-        pocketfft::detail::dst(dims, stride_in, stride_out, axes, type,
-                               X_data, Y_data, norm_factor, ortho, nthreads);
+        pocketfft::dst(dims, stride_in, stride_out, axes, type,
+                       X_data, Y_data, norm_factor, ortho, nthreads);
       }
       catch (const std::exception &e)
       {

test/test_runner.ml

@@ -37,4 +37,5 @@ let () =
     ; "base: complex", Unit_base_complex.test_set
     ; "base: ndarray core", Unit_base_ndarray_core.test_set
     ; "base: linalg", Unit_linalg_solver.test_set; "base: signal", Unit_signal.test_set
+    ; "fft", Unit_fft.test_set
     ; ("algodiff matrix", Unit_algodiff_matrix.[ Reverse.test; Forward.test ]) ]