fn test_clamped_normal()

in rd-hashd/src/hasher.rs [910:954]

• 39 lines of code
• 12 McCabe index (conditional complexity)

    fn test_clamped_normal() {
        let _ = ::env_logger::try_init();
        let mut rng = SmallRng::from_entropy();

        // 0 stdev should always give mean.
        println!("Testing ClampedNormal (0, 0) [-1, 1] == 0");
        let n = super::ClampedNormal::new(0.0, 0.0, -1.0, 1.0);
        for _ in 0..1024 {
            assert_eq!(n.sample(&mut rng), 0.0);
        }

        // Should behave like a normal distribution with strict bounds.
        println!("Testing ClampedNormal (1, 0.333333) [0, 2]");
        let mut ckms = CKMS::<f64>::new(CKMS_ERROR);
        let n = super::ClampedNormal::new(1.0, 0.333333, 0.0, 2.0);
        for _ in 0..4096 {
            let v = n.sample(&mut rng);
            assert!(v >= 0.0 && v <= 2.0);
            ckms.insert(v);
        }
        let p16 = ckms.query(0.16).unwrap().1;
        let p50 = ckms.query(0.5).unwrap().1;
        let p84 = ckms.query(0.84).unwrap().1;
        println!("p16={:.3} p50={:.3} p84={:.3}", p16, p50, p84);
        assert!(p16 >= 0.6 && p16 <= 0.7);
        assert!(p50 >= 0.9 && p50 <= 1.1);
        assert!(p84 >= 1.3 && p84 <= 1.4);

        // Should behave close to a uniform distribution.
        println!("Testing ClampedNormal (0, 10.0) [-1, 1]");
        let mut ckms = CKMS::<f64>::new(CKMS_ERROR);
        let n = super::ClampedNormal::new(0.0, 10.0, -1.0, 1.0);
        for _ in 0..4096 {
            let v = n.sample(&mut rng);
            assert!(v >= -1.0 && v <= 1.0);
            ckms.insert(v);
        }
        let p25 = ckms.query(0.25).unwrap().1;
        let p50 = ckms.query(0.5).unwrap().1;
        let p75 = ckms.query(0.75).unwrap().1;
        println!("p25={:.3} p50={:.3} p75={:.3}", p25, p50, p75);
        assert!(p25 >= -0.6 && p25 <= -0.4);
        assert!(p50 >= -0.1 && p50 <= 0.1);
        assert!(p75 >= 0.4 && p75 <= 0.6);
    }