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explicit.rs
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explicit.rs
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use std::marker::PhantomData;
use ndarray::prelude::*;
use super::traits::{EOM, TimeEvolution};
pub mod markers {
pub struct EulerMarker {}
pub struct HeunMarker {}
pub struct RK4Marker {}
}
pub struct Explicit<F: EOM<D>, D: Dimension, Marker> {
f: F,
dt: f64,
phantom_dim: PhantomData<D>,
phantom_marker: PhantomData<Marker>,
}
impl<F: EOM<D>, D: Dimension, Marker> Explicit<F, D, Marker> {
pub fn new(f: F, dt: f64) -> Self {
Explicit {
f: f,
dt: dt,
phantom_dim: PhantomData,
phantom_marker: PhantomData,
}
}
}
impl<F: EOM<D>, D: Dimension> TimeEvolution<D> for Explicit<F, D, markers::EulerMarker> {
#[inline(always)]
fn iterate(&self, x: RcArray<f64, D>) -> RcArray<f64, D> {
let fx = self.f.rhs(x.clone());
x + fx * self.dt
}
}
impl<F: EOM<D>, D: Dimension> TimeEvolution<D> for Explicit<F, D, markers::HeunMarker> {
#[inline(always)]
fn iterate(&self, x: RcArray<f64, D>) -> RcArray<f64, D> {
let k1 = self.dt * self.f.rhs(x.clone());
let k2 = self.dt * self.f.rhs(x.clone() + k1.clone());
x + 0.5 * (k1 + k2)
}
}
impl<F: EOM<D>, D: Dimension> TimeEvolution<D> for Explicit<F, D, markers::RK4Marker> {
#[inline(always)]
fn iterate(&self, x: RcArray<f64, D>) -> RcArray<f64, D> {
let k1 = self.f.rhs(x.clone());
let l1 = (0.5 * self.dt) * k1.clone() + &x;
let k2 = self.f.rhs(l1);
let l2 = (0.5 * self.dt) * k2.clone() + &x;
let k3 = self.f.rhs(l2);
let l3 = self.dt * k3.clone() + &x;
let k4 = self.f.rhs(l3);
x + (self.dt / 6.0) * (k1 + 2.0 * (k2 + k3) + k4)
}
}
pub fn euler<F: EOM<D>, D: Dimension>(f: F, dt: f64) -> Explicit<F, D, markers::EulerMarker> {
Explicit::new(f, dt)
}
pub fn heun<F: EOM<D>, D: Dimension>(f: F, dt: f64) -> Explicit<F, D, markers::HeunMarker> {
Explicit::new(f, dt)
}
pub fn rk4<F: EOM<D>, D: Dimension>(f: F, dt: f64) -> Explicit<F, D, markers::RK4Marker> {
Explicit::new(f, dt)
}