pub fn cosine_similarity(a: &[f32], b: &[f32]) -> f32 {
if a.len() != b.len() || a.is_empty() {
return 0.0;
}
let dot: f32 = a.iter().zip(b.iter()).map(|(x, y)| x * y).sum();
if dot.is_finite() {
dot
} else {
0.0
}
}
pub fn l2_normalize(v: &[f32]) -> Vec<f32> {
let norm: f32 = v.iter().map(|x| x * x).sum::<f32>().sqrt();
if norm > 0.0 {
v.iter().map(|x| x / norm).collect()
} else {
v.to_vec()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn cosine_identical_normalized() {
let v = [0.6, 0.8]; assert!((cosine_similarity(&v, &v) - 1.0).abs() < 1e-6);
}
#[test]
fn cosine_orthogonal() {
let a = [1.0, 0.0];
let b = [0.0, 1.0];
assert!((cosine_similarity(&a, &b)).abs() < 1e-6);
}
#[test]
fn cosine_empty() {
assert_eq!(cosine_similarity(&[], &[]), 0.0);
}
#[test]
fn cosine_mismatched_length() {
assert_eq!(cosine_similarity(&[1.0], &[1.0, 2.0]), 0.0);
}
#[test]
fn l2_normalize_basic() {
let v = l2_normalize(&[3.0, 4.0]);
let norm: f32 = v.iter().map(|x| x * x).sum::<f32>().sqrt();
assert!((norm - 1.0).abs() < 1e-6);
assert!((v[0] - 0.6).abs() < 1e-6);
assert!((v[1] - 0.8).abs() < 1e-6);
}
#[test]
fn l2_normalize_zero_vector() {
let v = l2_normalize(&[0.0, 0.0]);
assert_eq!(v, vec![0.0, 0.0]);
}
}