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shootout-nbody improvement

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- factorize operation
- factorize loop (and gain a level of indentation)
- ~5% faster

Thanks to @Ryman for the propositions :)
This commit is contained in:
Guillaume Pinot 2014-05-11 18:49:01 +02:00 committed by Alex Crichton
parent 48beab1205
commit 437338ab65
1 changed files with 20 additions and 23 deletions
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43
src/test/bench/shootout-nbody.rs
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@ -70,33 +70,30 @@ struct Planet {
fn advance(bodies: &mut [Planet, ..N_BODIES], dt: f64, steps: int) {
for _ in range(0, steps) {
{
let mut b_slice = bodies.as_mut_slice();
loop {
let bi = match b_slice.mut_shift_ref() {
Some(bi) => bi,
None => break
};
for bj in b_slice.mut_iter() {
let dx = bi.x - bj.x;
let dy = bi.y - bj.y;
let dz = bi.z - bj.z;
let mut b_slice = bodies.as_mut_slice();
loop {
let bi = match b_slice.mut_shift_ref() {
Some(bi) => bi,
None => break
};
for bj in b_slice.mut_iter() {
let dx = bi.x - bj.x;
let dy = bi.y - bj.y;
let dz = bi.z - bj.z;
let d2 = dx * dx + dy * dy + dz * dz;
let mag = dt / (d2 * d2.sqrt());
let d2 = dx * dx + dy * dy + dz * dz;
let mag = dt / (d2 * d2.sqrt());
bi.vx -= dx * bj.mass * mag;
bi.vy -= dy * bj.mass * mag;
bi.vz -= dz * bj.mass * mag;
let massj_mag = bj.mass * mag;
bi.vx -= dx * massj_mag;
bi.vy -= dy * massj_mag;
bi.vz -= dz * massj_mag;
bj.vx += dx * bi.mass * mag;
bj.vy += dy * bi.mass * mag;
bj.vz += dz * bi.mass * mag;
}
let massi_mag = bi.mass * mag;
bj.vx += dx * massi_mag;
bj.vy += dy * massi_mag;
bj.vz += dz * massi_mag;
}
}
for bi in bodies.mut_iter() {
bi.x += dt * bi.vx;
bi.y += dt * bi.vy;
bi.z += dt * bi.vz;