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use std::collections::VecDeque;
#[derive(Debug, Clone)]
pub struct Entropy {
value: f64,
window_len: usize,
q_vals: VecDeque<bool>,
}
impl Entropy {
#[inline(always)]
pub fn new(window_len: usize) -> Self {
Self {
value: 0.0,
window_len,
q_vals: VecDeque::new(),
}
}
#[inline]
pub fn update(&mut self, val: bool) {
if self.q_vals.len() >= self.window_len {
let _ = self.q_vals.pop_back().unwrap();
}
self.q_vals.push_front(val);
}
pub fn last(&self) -> f64 {
let c: f64 = self.q_vals.len() as f64;
let s: f64 = self
.q_vals
.iter()
.map(|v| if *v { 1.0 } else { 0.0 })
.sum::<f64>();
let pt: f64 = s / c;
let pn: f64 = 1.0 - pt;
let mut value = pt * pt.log2() + pn * pn.log2();
if value.is_nan() {
value = 0.0
}
-value
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn entropy() {
let vals: Vec<bool> = vec![false; 10];
let mut e = Entropy::new(10);
for v in &vals {
e.update(*v);
let last = e.last();
assert_eq!(last, 0.0);
}
let vals: Vec<bool> = vec![true; 10];
let mut e = Entropy::new(10);
for v in &vals {
e.update(*v);
let last = e.last();
assert_eq!(last, 0.0);
}
let vals: Vec<bool> = vec![false, true, false, true];
let mut e = Entropy::new(4);
for v in &vals {
e.update(*v);
let last = e.last();
println!("last: {}", last);
}
let last = e.last();
assert_eq!(last, 1.0);
}
}