numeric_algs/integration/
rk4.rs

1use super::{Integrator, StepSize};
2use crate::traits::State;
3
4pub struct RK4Integrator {
5    default_step: f64,
6}
7
8impl RK4Integrator {
9    pub fn new(step_size: f64) -> Self {
10        RK4Integrator {
11            default_step: step_size,
12        }
13    }
14
15    pub fn set_default_step(&mut self, step: f64) {
16        self.default_step = step;
17    }
18}
19
20impl<S: State> Integrator<S> for RK4Integrator {
21    fn propagate_in_place<D>(&mut self, start: &mut S, diff_eq: D, step_size: StepSize)
22    where
23        D: Fn(&S) -> S::Derivative,
24    {
25        let h = match step_size {
26            StepSize::UseDefault => self.default_step,
27            StepSize::Step(x) => x,
28        };
29
30        let k1 = diff_eq(start);
31        let k2 = diff_eq(&start.shift(&k1, h / 2.0));
32        let k3 = diff_eq(&start.shift(&k2, h / 2.0));
33        let k4 = diff_eq(&start.shift(&k3, h));
34
35        start.shift_in_place(&(k1 + k2 * 2.0 + k3 * 2.0 + k4), h / 6.0);
36    }
37}
numeric_algs/integration/rk4.rs

numeric_algs/integration/
rk4.rs
