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use serde::{Deserialize, Serialize};
use crate::math::num::RealNumber;
use super::Distance;
#[derive(Serialize, Deserialize, Debug, Clone)]
pub struct Minkowski {
pub p: u16,
}
impl<T: RealNumber> Distance<Vec<T>, T> for Minkowski {
fn distance(&self, x: &Vec<T>, y: &Vec<T>) -> T {
if x.len() != y.len() {
panic!("Input vector sizes are different");
}
if self.p < 1 {
panic!("p must be at least 1");
}
let mut dist = T::zero();
let p_t = T::from_u16(self.p).unwrap();
for i in 0..x.len() {
let d = (x[i] - y[i]).abs();
dist += d.powf(p_t);
}
dist.powf(T::one() / p_t)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn minkowski_distance() {
let a = vec![1., 2., 3.];
let b = vec![4., 5., 6.];
let l1: f64 = Minkowski { p: 1 }.distance(&a, &b);
let l2: f64 = Minkowski { p: 2 }.distance(&a, &b);
let l3: f64 = Minkowski { p: 3 }.distance(&a, &b);
assert!((l1 - 9.0).abs() < 1e-8);
assert!((l2 - 5.19615242).abs() < 1e-8);
assert!((l3 - 4.32674871).abs() < 1e-8);
}
#[test]
#[should_panic(expected = "p must be at least 1")]
fn minkowski_distance_negative_p() {
let a = vec![1., 2., 3.];
let b = vec![4., 5., 6.];
let _: f64 = Minkowski { p: 0 }.distance(&a, &b);
}
}