47 lines
1.1 KiB
Rust
47 lines
1.1 KiB
Rust
use super::grid::Grid;
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use super::operators::SbpOperator;
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use ndarray::{Array3, Zip};
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pub(crate) fn integrate_rk4<'a, F: 'a, SBP, RHS, WB>(
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rhs: RHS,
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prev: &F,
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fut: &mut F,
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dt: f32,
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grid: &Grid<SBP>,
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k: &mut [F; 4],
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mut wb: &mut WB,
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) where
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F: std::ops::Deref<Target = Array3<f32>> + std::ops::DerefMut<Target = Array3<f32>>,
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SBP: SbpOperator,
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RHS: Fn(&mut F, &F, &Grid<SBP>, &mut WB),
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{
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assert_eq!(prev.shape(), fut.shape());
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for i in 0..4 {
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// y = y0 + c*kn
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fut.assign(prev);
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match i {
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0 => {}
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1 | 2 => {
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fut.scaled_add(1.0 / 2.0 * dt, &k[i - 1]);
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}
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3 => {
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fut.scaled_add(dt, &k[i - 1]);
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}
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_ => {
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unreachable!();
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}
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};
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rhs(&mut k[i], &fut, grid, &mut wb);
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}
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Zip::from(&mut **fut)
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.and(&**prev)
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.and(&*k[0])
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.and(&*k[1])
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.and(&*k[2])
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.and(&*k[3])
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.apply(|y1, &y0, &k1, &k2, &k3, &k4| *y1 = y0 + dt / 6.0 * (k1 + 2.0 * k2 + 2.0 * k3 + k4));
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}
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