feffit 0.1.0

//! `gamma` (Cephes port) vs `scipy.special.gamma`.
//!
//! Reference generated by `scripts/ref_gamma.py`.

use feffit::feffdat::gamma;
use std::path::PathBuf;

fn data(name: &str) -> PathBuf {
    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .join("tests/data")
        .join(name)
}

#[test]
fn gamma_matches_scipy() {
    let text = std::fs::read_to_string(data("ref_gamma.txt")).unwrap();
    let mut max_rel = 0.0f64;
    let mut n = 0;
    for line in text.lines() {
        let line = line.trim();
        if line.is_empty() || line.starts_with('#') {
            continue;
        }
        let mut it = line.split_whitespace();
        let x: f64 = it.next().unwrap().parse().unwrap();
        let want: f64 = it.next().unwrap().parse().unwrap();
        let got = gamma(x);
        let rel = (got - want).abs() / want.abs();
        assert!(
            rel < 1e-12,
            "gamma({x}) = {got:e}, want {want:e}, rel {rel:e}"
        );
        max_rel = max_rel.max(rel);
        n += 1;
    }
    assert!(n >= 30, "parsed too few rows: {n}");
    eprintln!("gamma: {n} points, max rel err {max_rel:e}");
}