Updates

benches/bench.rs

@@ -10,7 +10,7 @@ use rand::{
     thread_rng, Rng,
 };
 use utilities::rustfft::num_complex::Complex;
-use utilities::rustfft::{FftNum, FftPlanner};
+use utilities::rustfft::FftPlanner;
 
 const LENGTHS: &[usize] = &[
     6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,

src/lib.rs

@@ -114,27 +114,44 @@ macro_rules! impl_fft_with_opts_and_plan_for {
                 _ => (),
             }
 
-            let mut filtered_twiddles_re = twiddles_re.clone();
-            let mut filtered_twiddles_im = twiddles_im.clone();
+            // 0th stage is special due to no need to filter twiddle factor
+            let dist = 1 << (n - 1);
+            let chunk_size = dist << 1;
+
+            if chunk_size > 4 {
+                if chunk_size >= $lanes * 2 {
+                    $simd_butterfly_kernel(reals, imags, twiddles_re, twiddles_im, dist);
+                } else {
+                    fft_chunk_n(reals, imags, twiddles_re, twiddles_im, dist);
+                }
+            }
+            else if chunk_size == 4 {
+                fft_chunk_4(reals, imags);
+            }
+            else if chunk_size == 2 {
+                fft_chunk_2(reals, imags);
+            }
+
+            let (mut filtered_twiddles_re, mut filtered_twiddles_im) = filter_twiddles(twiddles_re, twiddles_im);
 
-            for t in (0..n).rev() {
+            for t in (0..n - 1).rev() {
                 let dist = 1 << t;
                 let chunk_size = dist << 1;
 
                 if chunk_size > 4 {
-                    if t < n - 1 {
-                        (filtered_twiddles_re, filtered_twiddles_im) = filter_twiddles(&filtered_twiddles_re, &filtered_twiddles_im);
-                    }
                     if chunk_size >= $lanes * 2 {
                         $simd_butterfly_kernel(reals, imags, &filtered_twiddles_re, &filtered_twiddles_im, dist);
                     } else {
                         fft_chunk_n(reals, imags, &filtered_twiddles_re, &filtered_twiddles_im, dist);
                     }
-                } else if chunk_size == 2 {
-                    fft_chunk_2(reals, imags);
-                } else if chunk_size == 4 {
+                }
+                else if chunk_size == 4 {
                     fft_chunk_4(reals, imags);
                 }
+                else if chunk_size == 2 {
+                    fft_chunk_2(reals, imags);
+                }
+                (filtered_twiddles_re, filtered_twiddles_im) = filter_twiddles(&filtered_twiddles_re, &filtered_twiddles_im);
             }
 
             if opts.multithreaded_bit_reversal {

src/twiddles.rs

@@ -217,6 +217,34 @@ mod tests {
 
     use super::*;
 
+    // TODO(saveliy): use
+    #[test]
+    fn twiddles_cos_only() {
+        let n = 4;
+        let big_n = 1 << n;
+
+        let dist = big_n >> 1;
+
+        let (fwd_twiddles_re, fwd_twiddles_im) = if dist >= 8 * 2 {
+            generate_twiddles_simd_64(dist, Direction::Forward)
+        } else {
+            generate_twiddles(dist, Direction::Forward)
+        };
+
+        assert!(fwd_twiddles_re.len() == dist && fwd_twiddles_im.len() == dist);
+
+        for i in 0..dist {
+            let w_re = fwd_twiddles_re[i];
+            let expected_w_im = fwd_twiddles_im[i];
+
+            let actual_w_im = -fwd_twiddles_re[(i + dist / 2) % dist];
+            //assert_float_closeness(actual_w_im, expected_w_im, 1e-6);
+            print!("actual: {actual_w_im} expected: {expected_w_im}\n");
+        }
+        println!("{:?}", fwd_twiddles_re);
+        println!("{:?}", fwd_twiddles_im);
+    }
+
     #[test]
     fn twiddles_4() {
         const N: usize = 4;