catlog/simulate/ode/
linear_ode.rs

1//! Constant-coefficient linear first-order differential equations.
2
3use nalgebra::{DMatrix, DVector};
4
5#[cfg(test)]
6use super::ODEProblem;
7use super::ODESystem;
8
9/** A (constant-coefficient) linear (first-order) dynamical system.
10
11A system of linear first-order ODEs with constant coefficients; a semantics for
12causal loop diagrams.
13*/
14#[derive(Clone, Debug, PartialEq)]
15pub struct LinearODESystem {
16    coefficients: DMatrix<f32>,
17}
18
19impl LinearODESystem {
20    /// Create a new LinearODE system.
21    pub fn new(A: DMatrix<f32>) -> Self {
22        Self { coefficients: A }
23    }
24}
25
26impl ODESystem for LinearODESystem {
27    fn vector_field(&self, dx: &mut DVector<f32>, x: &DVector<f32>, _t: f32) {
28        let A = &self.coefficients;
29        *dx = A * x
30    }
31}
32
33#[cfg(test)]
34pub(crate) fn create_neg_loops_pos_connector() -> ODEProblem<LinearODESystem> {
35    use nalgebra::{dmatrix, dvector};
36
37    let A = dmatrix![-0.3,  0.0,  0.0;
38                      0.0,  0.0,  0.5;
39                      1.0, -2.0,  0.0];
40    let system = LinearODESystem::new(A);
41    let initial = dvector![2.0, 1.0, 1.0];
42    ODEProblem::new(system, initial).end_time(10.0)
43}
44
45#[cfg(test)]
46mod tests {
47    use expect_test::expect;
48
49    use super::super::textplot_ode_result;
50    use super::*;
51
52    #[test]
53    fn neg_loops_pos_connector() {
54        let problem = create_neg_loops_pos_connector();
55        let result = problem.solve_rk4(0.1).unwrap();
56        let expected = expect![["
57            ⡑⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ 2.0
58            ⠄⠈⠢⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
59            ⠂⠀⠀⠈⠢⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
60            ⡁⠀⠀⣀⠤⠚⠲⣒⢄⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠔⠁⠀⠑⢄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
61            ⠄⡠⠊⠀⠀⠀⠀⠀⠑⠬⣆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⠃⠀⠀⠀⠀⠈⢆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
62            ⠚⢄⠀⠀⠀⠀⠀⠀⠀⠀⠈⠳⡤⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⠃⠀⠀⠀⠀⠀⠀⠈⡆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
63            ⡁⠀⠱⡀⠀⠀⠀⠀⠀⠀⠀⠀⠑⡄⠑⠢⢄⡀⠀⠀⠀⠀⠀⠀⠀⢀⠎⠀⠀⠀⠀⠀⠀⠀⠀⢘⡔⠊⠉⠉⠒⢄⠀⠀⠀⠀⠀⠀⠀⠀⠀
64            ⠄⠀⠀⠱⡀⠀⠀⠀⠀⠀⠀⠀⠀⠘⡄⠀⠀⠈⠉⠒⠤⢄⣀⠀⠀⡜⠀⠀⠀⠀⠀⠀⠀⢀⠔⠁⢱⠀⠀⠀⠀⠀⠑⢄⠀⠀⠀⠀⠀⠀⠀
65            ⠂⠀⠀⠀⢣⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⡄⠀⠀⠀⠀⠀⠀⠀⠉⢱⠓⠢⠤⢄⣀⡀⠀⡠⠃⠀⠀⠀⢇⠀⠀⠀⠀⠀⠈⢢⠀⠀⠀⠀⠀⠀
66            ⡁⠀⠀⠀⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⢄⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠈⡝⠉⠑⠒⠒⠢⠼⡤⠤⢄⣀⣀⣀⣀⡱⡀⠀⠀⠀⠀
67            ⡄⢀⠀⡀⢀⠘⡄⢀⠀⡀⢀⠀⡀⢀⠀⡀⢈⢆⡀⢀⠀⡀⢀⡸⡀⢀⠀⡀⢀⢀⡎⢀⠀⡀⢀⠀⡀⢀⢣⡀⢀⠀⡀⢀⠀⡈⢙⡍⡉⢉⠁
68            ⠂⠀⠀⠀⠀⠀⢱⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢢⠀⠀⠀⢠⠃⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠈⡆⠀⠀⠀⠀⠀⠀⠀⠘⢄⠀⠀
69            ⡁⠀⠀⠀⠀⠀⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠑⢄⠀⡜⠀⠀⠀⢀⠔⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠈⢢⠀
70            ⠄⠀⠀⠀⠀⠀⠀⠘⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢱⠣⠤⠤⠒⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠁
71            ⠂⠀⠀⠀⠀⠀⠀⠀⢱⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀
72            ⡁⠀⠀⠀⠀⠀⠀⠀⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠱⡀⠀⠀⠀⠀⠀⠀⠀⠀
73            ⠄⠀⠀⠀⠀⠀⠀⠀⠀⠘⡄⠀⠀⠀⠀⠀⠀⠀⠀⢠⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢣⠀⠀⠀⠀⠀⠀⠀⠀
74            ⠂⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⡄⠀⠀⠀⠀⠀⠀⢀⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢣⠀⠀⠀⠀⠀⡠⠂
75            ⡁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠱⡀⠀⠀⠀⠀⢀⠎⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠑⢄⠀⢀⡰⠁⠀
76            ⠄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⢄⡀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠁⠀⠀⠀
77            ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠉⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ -1.8
78            0.0                                           10.0
79            "]];
80        expected.assert_eq(&textplot_ode_result(&problem, &result));
81    }
82}
catlog/simulate/ode/linear_ode.rs

catlog/simulate/ode/
linear_ode.rs
