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
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92

use ndarray::{
    ArrayBase,
    Data,
    Dimension
};

use ode::Ode;

mod impl_euler;
mod impl_heun;
mod impl_runge_kutta_4;

#[cfg(feature="tuple")]
mod tuple_impls;

pub struct Euler<T> {
    dt: f64,

    temp: T,
}

pub struct Heun<T> {
    dt: f64,
    dt_2: f64,

    temp: T,
    k1: T,
    k2: T,
}

pub struct RungeKutta4<T> {
    dt: f64,
    dt_2: f64,
    dt_3: f64,
    dt_6: f64,

    temp: T,

    k1: T,
    k2: T,
    k3: T,
    k4: T,
}

/// A trait defining the interface of an integration method.
pub trait Stepper
{
    type State: Clone;

    fn do_step<Sy>(&mut self, &mut Sy, &mut Self::State)
        where Sy: Ode<State = Self::State>;

    fn timestep(&self) -> f64;

    fn integrate_n_steps<Sy>(&mut self, system: &mut Sy, state: &mut Self::State, n: usize) -> f64
        where Sy: Ode<State = Self::State>
    {
        let mut tacc = 0f64;;

        let dt = self.timestep();

        // Ensure t is not exceeded
        for _ in 0..n {
            self.do_step(system, state);
            tacc += dt;
        }
        tacc
    }

    fn integrate_time<Sy>(&mut self, system: &mut Sy, state: &mut Self::State, t: f64) -> (f64, usize)
        where Sy: Ode<State = Self::State>
    {
        let mut tacc = 0f64;;
        let mut count = 0;

        let dt = self.timestep();

        // Ensure t is not exceeded
        while (tacc + dt) <= t {
            self.do_step(system, state);
            tacc += dt;
            count += 1;
        }
        (tacc, count)
    }
}

/// An internal marker trait to avoid trait impl conflicts.
pub trait ZipMarker {}

impl<T> ZipMarker for Vec<T> {}
impl<D: Dimension, S: Data> ZipMarker for ArrayBase<S,D> {}