viffy 0.1.5

SoA + SIMD automata generator
Documentation 
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/// Dead Reckoning Algorithm
pub fn dead_reckoning(size: (usize, usize), i: &[f32], d: &mut [f32]) {
	const RT_2: f32 = 1.41421356237309504;
	unsafe {
		std::hint::assert_unchecked(i.len() >= size.0 * size.1);
		std::hint::assert_unchecked(d.len() >= size.0 * size.1);
		std::hint::assert_unchecked(size.0 > 0);
		std::hint::assert_unchecked(size.0 < 32767);
		std::hint::assert_unchecked(size.1 > 0);
		std::hint::assert_unchecked(size.1 < 32767);
		std::hint::assert_unchecked(size.0 % 4 == 0);
		std::hint::assert_unchecked(size.1 % 4 == 0);
		std::hint::assert_unchecked(size.0 * size.1 > 0);
	}
	d.fill(f32::INFINITY);
	let mut px = vec![0; size.0 * size.1];
	let mut py = vec![0; size.0 * size.1];
	for y in 1..(size.1 - 1) {
		for x in 1..(size.0 - 1) {
			if i[x - 1 + size.0 * y] != i[x + size.0 * y]
			|| i[x + 1 + size.0 * y] != i[x + size.0 * y]
			|| i[x + size.0 * (y + 1)] != i[x + size.0 * y]
			|| i[x + size.0 * (y - 1)] != i[x + size.0 * y] {
				d[x + size.0 * y] = 0.0;
				px[x + size.0 * y] = x;
				py[x + size.0 * y] = y;
			}
		}
	}
	for y in 1..(size.1 - 1) {
		for x in 1..(size.0 - 1) {
			if d[(x - 1) + size.0 * (y - 1)] + RT_2 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x - 1) + size.0 * (y - 1)];
				px[x + size.0 * y] = px[(x - 1) + size.0 * (y - 1)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
			if d[(x) + size.0 * (y - 1)] + 1.0 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x) + size.0 * (y - 1)];
				px[x + size.0 * y] = px[(x) + size.0 * (y - 1)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
			if d[(x + 1) + size.0 * (y - 1)] + RT_2 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x + 1) + size.0 * (y - 1)];
				px[x + size.0 * y] = px[(x + 1) + size.0 * (y - 1)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
			if d[(x - 1) + size.0 * (y)] + 1.0 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x - 1) + size.0 * (y)];
				px[x + size.0 * y] = px[(x - 1) + size.0 * (y)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
		}
	}
	for y in (1..size.1 - 2).rev() {
		for x in (1..size.0 - 2).rev() {
			if d[(x + 1) + size.0 * (y)] + 1.0 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x + 1) + size.0 * (y)];
				px[x + size.0 * y] = px[(x + 1) + size.0 * (y)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
			if d[(x - 1) + size.0 * (y + 1)] + RT_2 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x - 1) + size.0 * (y + 1)];
				px[x + size.0 * y] = px[(x - 1) + size.0 * (y + 1)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
			if d[(x) + size.0 * (y + 1)] + 1.0 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x) + size.0 * (y + 1)];
				px[x + size.0 * y] = px[(x) + size.0 * (y + 1)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
			if d[(x + 1) + size.0 * (y + 1)] + RT_2 < d[(x) + size.0 * (y)] {
				py[x + size.0 * y] = py[(x + 1) + size.0 * (y + 1)];
				px[x + size.0 * y] = px[(x + 1) + size.0 * (y + 1)];
				let dpx = x - px[x + size.0 * y];
				let dpy = y - py[x + size.0 * y];
				d[(x) + size.0 * (y)] = ((dpx * dpx + dpy * dpy) as f32).sqrt();
			}
		}
	}
	for xy in 0..(size.0 * size.1) {
		if i[xy] != 0.0 {
			d[xy] *= -1.0;
		}
	}
}

/// See https://en.wikipedia.org/wiki/Simpson%27s_rule
pub fn simpsons_rule(a: f32, b: f32, mut f: impl FnMut(f32) -> f32) -> f32 {
	((b - a) / 6.0) * (f(a) + 4.0 * f((a + b) / 2.0) + f(b))
}