Add Planner and ammend examples, tests, etc.

examples/benchmark.rs

@@ -1,7 +1,8 @@
 use std::env;
 use std::str::FromStr;
 
-use phastft::fft_dif;
+use phastft::fft;
+use phastft::planner::Planner;
 use utilities::gen_random_signal;
 
 fn benchmark_fft(n: usize) {
@@ -11,7 +12,8 @@ fn benchmark_fft(n: usize) {
     gen_random_signal(&mut reals, &mut imags);
 
     let now = std::time::Instant::now();
-    fft_dif(&mut reals, &mut imags);
+    let mut planner = Planner::new(n);
+    fft(&mut reals, &mut imags, &mut planner);
     let elapsed = now.elapsed().as_micros();
     println!("{elapsed}");
 }

examples/profile.rs

@@ -1,13 +1,15 @@
 use std::env;
 use std::str::FromStr;
 
-use phastft::fft_dif;
+use phastft::fft;
+use phastft::planner::Planner;
 
 fn benchmark_fft(num_qubits: usize) {
     let n = 1 << num_qubits;
-    let mut reals: Vec<f64> = (1..=n).map(f64::from).collect();
-    let mut imags: Vec<f64> = (1..=n).map(f64::from).collect();
-    fft_dif(&mut reals, &mut imags);
+    let mut reals: Vec<f64> = (1..=n).map(|i| i as f64).collect();
+    let mut imags: Vec<f64> = (1..=n).map(|i| i as f64).collect();
+    let mut planner = Planner::new(n);
+    fft(&mut reals, &mut imags, &mut planner);
 }
 
 fn main() {

src/lib.rs

@@ -3,68 +3,62 @@
 use crate::cobra::cobra_apply;
 use crate::kernels::{fft_chunk_2, fft_chunk_4, fft_chunk_n, fft_chunk_n_simd, Float};
 use crate::options::Options;
-use crate::twiddles::{filter_twiddles, generate_twiddles, generate_twiddles_simd};
+use crate::planner::Planner;
+use crate::twiddles::filter_twiddles;
 
 mod cobra;
 mod kernels;
 pub mod options;
+pub mod planner;
 mod twiddles;
 
 /// FFT -- Decimation in Frequency
 ///
 /// This is just the decimation-in-time algorithm, reversed.
-/// The inputs are in normal order, and the outputs are bit reversed.
+/// The inputs are in normal order, and the outputs are then bit reversed.
 ///
 /// # Panics
 ///
 /// Panics if `reals.len() != imags.len()`
 ///
 /// [1] https://inst.eecs.berkeley.edu/~ee123/sp15/Notes/Lecture08_FFT_and_SpectAnalysis.key.pdf
-pub fn fft_dif(reals: &mut [Float], imags: &mut [Float]) {
+pub fn fft(reals: &mut [Float], imags: &mut [Float], planner: &mut Planner) {
     let opts = Options::guess_options(reals.len());
-    fft_dif_with_opts(reals, imags, &opts)
+    fft_with_opts(reals, imags, &opts, planner);
 }
 
-/// Same as [fft_dif], but also accepts [`Options`] that control optimization strategies.
+/// Same as [fft], but also accepts [`Options`] that control optimization strategies.
 ///
 /// `fft_dif` automatically guesses the best strategy for a given input,
 /// so you only need to call this if you are tuning performance for a specific hardware platform.
-pub fn fft_dif_with_opts(reals: &mut [Float], imags: &mut [Float], opts: &Options) {
+///
+/// # Panics
+///
+/// Panics if `reals.len() != imags.len()`
+pub fn fft_with_opts(
+    reals: &mut [Float],
+    imags: &mut [Float],
+    opts: &Options,
+    planner: &mut Planner,
+) {
     assert_eq!(reals.len(), imags.len());
     let n: usize = reals.len().ilog2() as usize;
 
-    let dist = 1 << (n - 1);
-    let chunk_size = dist << 1;
-    let (mut twiddles_re, mut twiddles_im) = if dist >= 8 * 2 {
-        generate_twiddles_simd(dist)
-    } else {
-        generate_twiddles(dist)
-    };
+    let twiddles_re = &mut planner.twiddles_re;
+    let twiddles_im = &mut planner.twiddles_im;
 
-    assert_eq!(twiddles_re.len(), twiddles_im.len());
-
-    if chunk_size > 4 {
-        if chunk_size >= 16 {
-            fft_chunk_n_simd(reals, imags, &twiddles_re, &twiddles_im, dist);
-        } else {
-            fft_chunk_n(reals, imags, &twiddles_re, &twiddles_im, dist);
-        }
-    } else if chunk_size == 2 {
-        fft_chunk_2(reals, imags);
-    } else if chunk_size == 4 {
-        fft_chunk_4(reals, imags);
-    }
-
-    for t in (0..n - 1).rev() {
+    for t in (0..n).rev() {
         let dist = 1 << t;
         let chunk_size = dist << 1;
 
         if chunk_size > 4 {
-            filter_twiddles(&mut twiddles_re, &mut twiddles_im);
+            if t < n - 1 {
+                filter_twiddles(twiddles_re, twiddles_im);
+            }
             if chunk_size >= 16 {
-                fft_chunk_n_simd(reals, imags, &twiddles_re, &twiddles_im, dist);
+                fft_chunk_n_simd(reals, imags, twiddles_re, twiddles_im, dist);
             } else {
-                fft_chunk_n(reals, imags, &twiddles_re, &twiddles_im, dist);
+                fft_chunk_n(reals, imags, twiddles_re, twiddles_im, dist);
             }
         } else if chunk_size == 2 {
             fft_chunk_2(reals, imags);
@@ -96,18 +90,19 @@ mod tests {
     use super::*;
 
     #[test]
-    fn fft() {
+    fn fft_correctness() {
         let range = Range { start: 4, end: 17 };
 
         for k in range {
-            let n = 1 << k;
+            let n: usize = 1 << k;
 
-            let mut reals: Vec<Float> = (1..=n).map(f64::from).collect();
-            let mut imags: Vec<Float> = (1..=n).map(f64::from).collect();
-            fft_dif(&mut reals, &mut imags);
+            let mut reals: Vec<Float> = (1..=n).map(|i| i as f64).collect();
+            let mut imags: Vec<Float> = (1..=n).map(|i| i as f64).collect();
+            let mut planner = Planner::new(n);
+            fft(&mut reals, &mut imags, &mut planner);
 
             let mut buffer: Vec<Complex64> = (1..=n)
-                .map(|i| Complex64::new(f64::from(i), f64::from(i)))
+                .map(|i| Complex64::new(i as f64, i as f64))
                 .collect();
 
             let mut planner = FftPlanner::new();