fn mul()

in math/src/field/f128/tests.rs [62:101]

• 30 lines of code
• 3 McCabe index (conditional complexity)

fn mul() {
    // identity
    let r: BaseElement = rand_value();
    assert_eq!(BaseElement::ZERO, r * BaseElement::ZERO);
    assert_eq!(r, r * BaseElement::ONE);

    // test multiplication within bounds
    assert_eq!(
        BaseElement::from(15u8),
        BaseElement::from(5u8) * BaseElement::from(3u8)
    );

    // test overflow
    let m = BaseElement::MODULUS;
    let t = BaseElement::from(m - 1);
    assert_eq!(BaseElement::ONE, t * t);
    assert_eq!(BaseElement::from(m - 2), t * BaseElement::from(2u8));
    assert_eq!(BaseElement::from(m - 4), t * BaseElement::from(4u8));

    let t = (m + 1) / 2;
    assert_eq!(
        BaseElement::ONE,
        BaseElement::from(t) * BaseElement::from(2u8)
    );

    // test random values
    let v1: Vec<BaseElement> = rand_vector(1000);
    let v2: Vec<BaseElement> = rand_vector(1000);
    for i in 0..v1.len() {
        let r1 = v1[i];
        let r2 = v2[i];

        let expected = (r1.to_big_uint() * r2.to_big_uint()) % BigUint::from(M);
        let expected = BaseElement::from_big_uint(expected);

        if expected != r1 * r2 {
            assert_eq!(expected, r1 * r2, "failed for: {} * {}", r1, r2);
        }
    }
}