1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

use ndarray::{Array1, Array2};

pub mod quadratic_cost;

pub struct CostFunction {
    pub f: fn(&Array1<f64>, &Array1<f64>) -> f64,
    pub d: fn(&Array1<f64>, &Array1<f64>) -> Array1<f64>,
}

impl CostFunction {
    pub fn cost(&self, a: &Array2<f64>, expected: &Array2<f64>) -> f64 {
        let mut cost = 0.0;
        for (a, expected) in a.outer_iter().zip(expected.outer_iter()) {
            cost += (self.f)(&a.to_owned(), &expected.to_owned());
        }
        cost / a.nrows() as f64
    }

    pub fn cost_derivative(&self, a: &Array2<f64>, expected: &Array2<f64>) -> Array2<f64> {
        let mut cost_derivative = Array2::zeros(a.raw_dim());

        for i in 0..a.ncols() {
            cost_derivative
                .column_mut(i)
                .assign(&((self.d)(&a.column(i).to_owned(), &expected.column(i).to_owned())));
        }

        cost_derivative
    }
}