mgh 0.1.16

A Collection of Moré-Garbow-Hilstrom https://dl.acm.org/doi/pdf/10.1145/355934.355936
Documentation 
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pub fn wood(x: &[f64]) -> f64 {
    let &[x1, x2, x3, x4] = x else {
        panic!("input dimension must be 4");
    };
    // f_1(x) = 10(x_2 - x_1^2)
    let f1 = 10. * (x2 - x1.powi(2));

    // f_2(x) = 1 - x_1
    let f2 = 1. - x1;

    // f_3(x) = (90)^0.5(x_4 - x_3^2)
    let f3 = 90.0_f64.sqrt() * (x4 - x3.powi(2));

    // f_4(x) = 1 - x_3
    let f4 = 1. - x3;

    // f_5(x) = (10)^0.5(x_2 + x_4 - 2)
    let f5 = 10.0_f64.sqrt() * (x2 + x4 - 2.);

    // f_6(x) = (10)^-0.5(x_2 - x_4)
    let f6 = 10.0_f64.sqrt().recip() * (x2 - x4);

    f1.powi(2) + f2.powi(2) + f3.powi(2) + f4.powi(2) + f5.powi(2) + f6.powi(2)
}

pub fn init() -> Vec<f64> {
    vec![-3., -1., -3., -1.]
}

pub fn min() -> Vec<f64> {
    vec![1., 1., 1., 1.]
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_wood() {
        let x = init();
        let val = wood(&x);
        assert!(val.is_finite());
    }

    #[test]
    fn test_min() {
        let x = min();
        let val = wood(&x);
        assert_eq!(val, 0.);
    }
}