YAPC::EU 2018 Glasgow Update!

Task/Fast-Fourier-transform/Rust/fast-fourier-transform.rust

@@ -0,0 +1,61 @@
+extern crate num;
+use num::complex::Complex;
+use std::f64::consts::PI;
+
+const I: Complex<f64> = Complex { re: 0.0, im: 1.0 };
+
+pub fn fft(input: &[Complex<f64>]) -> Vec<Complex<f64>> {
+    fn fft_inner(
+        buf_a: &mut [Complex<f64>],
+        buf_b: &mut [Complex<f64>],
+        n: usize,    // total length of the input array
+        step: usize, // precalculated values for t
+    ) {
+        if step >= n {
+            return;
+        }
+
+        fft_inner(buf_b, buf_a, n, step * 2);
+        fft_inner(&mut buf_b[step..], &mut buf_a[step..], n, step * 2);
+        // create a slice for each half of buf_a:
+        let (left, right) = buf_a.split_at_mut(n / 2);
+
+        for i in (0..n).step_by(step * 2) {
+            let t = (-I * PI * (i as f64) / (n as f64)).exp() * buf_b[i + step];
+            left[i / 2] = buf_b[i] + t;
+            right[i / 2] = buf_b[i] - t;
+        }
+    }
+
+    // round n (length) up to a power of 2:
+    let n_orig = input.len();
+    let n = n_orig.next_power_of_two();
+    // copy the input into a buffer:
+    let mut buf_a = input.to_vec();
+    // right pad with zeros to a power of two:
+    buf_a.append(&mut vec![Complex { re: 0.0, im: 0.0 }; n - n_orig]);
+    // alternate between buf_a and buf_b to avoid allocating a new vector each time:
+    let mut buf_b = buf_a.clone();
+    fft_inner(&mut buf_a, &mut buf_b, n, 1);
+    buf_a
+}
+
+fn show(label: &str, buf: &[Complex<f64>]) {
+    println!("{}", label);
+    let string = buf
+        .into_iter()
+        .map(|x| format!("{:.4}{:+.4}i", x.re, x.im))
+        .collect::<Vec<_>>()
+        .join(", ");
+    println!("{}", string);
+}
+
+fn main() {
+    let input: Vec<_> = [1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0]
+        .into_iter()
+        .map(|x| Complex::from(x))
+        .collect();
+    show("input:", &input);
+    let output = fft(&input);
+    show("output:", &output);
+}

Task/Fast-Fourier-transform/SystemVerilog/fast-fourier-transform-1.v

@@ -1,7 +1,3 @@
-/// @Author: Alexandre Felipe (o.alexandre.felipe@gmail.com)
-/// @Date: 2018-Jan-25
-///
-
 package math_pkg;
   // Inspired by the post
   // https://community.cadence.com/cadence_blogs_8/b/fv/posts/create-a-sine-wave-generator-using-systemverilog