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auto merge of #14090 : TeXitoi/rust/shootout-nbody-improvement, r=alexcrichton
- minimize bound check - factorise operations - use x, y, z instead of [f64, ..3] - ~1.15 faster
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src/test/bench/shootout-nbody.rs

Lines changed: 87 additions & 97 deletions
Original file line numberDiff line numberDiff line change
@@ -8,8 +8,6 @@
88
// option. This file may not be copied, modified, or distributed
99
// except according to those terms.
1010

11-
use std::os;
12-
1311
static PI: f64 = 3.141592653589793;
1412
static SOLAR_MASS: f64 = 4.0 * PI * PI;
1513
static YEAR: f64 = 365.24;
@@ -18,151 +16,143 @@ static N_BODIES: uint = 5;
1816
static BODIES: [Planet, ..N_BODIES] = [
1917
// Sun
2018
Planet {
21-
x: [ 0.0, 0.0, 0.0 ],
22-
v: [ 0.0, 0.0, 0.0 ],
19+
x: 0.0, y: 0.0, z: 0.0,
20+
vx: 0.0, vy: 0.0, vz: 0.0,
2321
mass: SOLAR_MASS,
2422
},
2523
// Jupiter
2624
Planet {
27-
x: [
28-
4.84143144246472090e+00,
29-
-1.16032004402742839e+00,
30-
-1.03622044471123109e-01,
31-
],
32-
v: [
33-
1.66007664274403694e-03 * YEAR,
34-
7.69901118419740425e-03 * YEAR,
35-
-6.90460016972063023e-05 * YEAR,
36-
],
25+
x: 4.84143144246472090e+00,
26+
y: -1.16032004402742839e+00,
27+
z: -1.03622044471123109e-01,
28+
vx: 1.66007664274403694e-03 * YEAR,
29+
vy: 7.69901118419740425e-03 * YEAR,
30+
vz: -6.90460016972063023e-05 * YEAR,
3731
mass: 9.54791938424326609e-04 * SOLAR_MASS,
3832
},
3933
// Saturn
4034
Planet {
41-
x: [
42-
8.34336671824457987e+00,
43-
4.12479856412430479e+00,
44-
-4.03523417114321381e-01,
45-
],
46-
v: [
47-
-2.76742510726862411e-03 * YEAR,
48-
4.99852801234917238e-03 * YEAR,
49-
2.30417297573763929e-05 * YEAR,
50-
],
35+
x: 8.34336671824457987e+00,
36+
y: 4.12479856412430479e+00,
37+
z: -4.03523417114321381e-01,
38+
vx: -2.76742510726862411e-03 * YEAR,
39+
vy: 4.99852801234917238e-03 * YEAR,
40+
vz: 2.30417297573763929e-05 * YEAR,
5141
mass: 2.85885980666130812e-04 * SOLAR_MASS,
5242
},
5343
// Uranus
5444
Planet {
55-
x: [
56-
1.28943695621391310e+01,
57-
-1.51111514016986312e+01,
58-
-2.23307578892655734e-01,
59-
],
60-
v: [
61-
2.96460137564761618e-03 * YEAR,
62-
2.37847173959480950e-03 * YEAR,
63-
-2.96589568540237556e-05 * YEAR,
64-
],
45+
x: 1.28943695621391310e+01,
46+
y: -1.51111514016986312e+01,
47+
z: -2.23307578892655734e-01,
48+
vx: 2.96460137564761618e-03 * YEAR,
49+
vy: 2.37847173959480950e-03 * YEAR,
50+
vz: -2.96589568540237556e-05 * YEAR,
6551
mass: 4.36624404335156298e-05 * SOLAR_MASS,
6652
},
6753
// Neptune
6854
Planet {
69-
x: [
70-
1.53796971148509165e+01,
71-
-2.59193146099879641e+01,
72-
1.79258772950371181e-01,
73-
],
74-
v: [
75-
2.68067772490389322e-03 * YEAR,
76-
1.62824170038242295e-03 * YEAR,
77-
-9.51592254519715870e-05 * YEAR,
78-
],
55+
x: 1.53796971148509165e+01,
56+
y: -2.59193146099879641e+01,
57+
z: 1.79258772950371181e-01,
58+
vx: 2.68067772490389322e-03 * YEAR,
59+
vy: 1.62824170038242295e-03 * YEAR,
60+
vz: -9.51592254519715870e-05 * YEAR,
7961
mass: 5.15138902046611451e-05 * SOLAR_MASS,
8062
},
8163
];
8264

8365
struct Planet {
84-
x: [f64, ..3],
85-
v: [f64, ..3],
66+
x: f64, y: f64, z: f64,
67+
vx: f64, vy: f64, vz: f64,
8668
mass: f64,
8769
}
8870

89-
fn advance(bodies: &mut [Planet, ..N_BODIES], dt: f64, steps: i32) {
90-
let mut d = [ 0.0, ..3 ];
71+
fn advance(bodies: &mut [Planet, ..N_BODIES], dt: f64, steps: int) {
9172
for _ in range(0, steps) {
92-
for i in range(0u, N_BODIES) {
93-
for j in range(i + 1, N_BODIES) {
94-
d[0] = bodies[i].x[0] - bodies[j].x[0];
95-
d[1] = bodies[i].x[1] - bodies[j].x[1];
96-
d[2] = bodies[i].x[2] - bodies[j].x[2];
97-
98-
let d2 = d[0]*d[0] + d[1]*d[1] + d[2]*d[2];
99-
let mag = dt / (d2 * d2.sqrt());
100-
101-
let a_mass = bodies[i].mass;
102-
let b_mass = bodies[j].mass;
103-
bodies[i].v[0] -= d[0] * b_mass * mag;
104-
bodies[i].v[1] -= d[1] * b_mass * mag;
105-
bodies[i].v[2] -= d[2] * b_mass * mag;
106-
107-
bodies[j].v[0] += d[0] * a_mass * mag;
108-
bodies[j].v[1] += d[1] * a_mass * mag;
109-
bodies[j].v[2] += d[2] * a_mass * mag;
73+
{
74+
let mut b_slice = bodies.as_mut_slice();
75+
loop {
76+
let bi = match b_slice.mut_shift_ref() {
77+
Some(bi) => bi,
78+
None => break
79+
};
80+
for bj in b_slice.mut_iter() {
81+
let dx = bi.x - bj.x;
82+
let dy = bi.y - bj.y;
83+
let dz = bi.z - bj.z;
84+
85+
let d2 = dx * dx + dy * dy + dz * dz;
86+
let mag = dt / (d2 * d2.sqrt());
87+
88+
bi.vx -= dx * bj.mass * mag;
89+
bi.vy -= dy * bj.mass * mag;
90+
bi.vz -= dz * bj.mass * mag;
91+
92+
bj.vx += dx * bi.mass * mag;
93+
bj.vy += dy * bi.mass * mag;
94+
bj.vz += dz * bi.mass * mag;
95+
}
11096
}
11197
}
11298

113-
for a in bodies.mut_iter() {
114-
a.x[0] += dt * a.v[0];
115-
a.x[1] += dt * a.v[1];
116-
a.x[2] += dt * a.v[2];
99+
for bi in bodies.mut_iter() {
100+
bi.x += dt * bi.vx;
101+
bi.y += dt * bi.vy;
102+
bi.z += dt * bi.vz;
117103
}
118104
}
119105
}
120106

121107
fn energy(bodies: &[Planet, ..N_BODIES]) -> f64 {
122108
let mut e = 0.0;
123-
let mut d = [ 0.0, ..3 ];
124-
for i in range(0u, N_BODIES) {
125-
for k in range(0u, 3) {
126-
e += bodies[i].mass * bodies[i].v[k] * bodies[i].v[k] / 2.0;
127-
}
128-
129-
for j in range(i + 1, N_BODIES) {
130-
for k in range(0u, 3) {
131-
d[k] = bodies[i].x[k] - bodies[j].x[k];
132-
}
133-
let dist = (d[0]*d[0] + d[1]*d[1] + d[2]*d[2]).sqrt();
134-
e -= bodies[i].mass * bodies[j].mass / dist;
109+
let mut bodies = bodies.as_slice();
110+
loop {
111+
let bi = match bodies.shift_ref() {
112+
Some(bi) => bi,
113+
None => break
114+
};
115+
e += (bi.vx * bi.vx + bi.vy * bi.vy + bi.vz * bi.vz) * bi.mass / 2.0;
116+
for bj in bodies.iter() {
117+
let dx = bi.x - bj.x;
118+
let dy = bi.y - bj.y;
119+
let dz = bi.z - bj.z;
120+
let dist = (dx * dx + dy * dy + dz * dz).sqrt();
121+
e -= bi.mass * bj.mass / dist;
135122
}
136123
}
137124
e
138125
}
139126

140127
fn offset_momentum(bodies: &mut [Planet, ..N_BODIES]) {
141-
for i in range(0u, N_BODIES) {
142-
for k in range(0u, 3) {
143-
bodies[0].v[k] -= bodies[i].v[k] * bodies[i].mass / SOLAR_MASS;
144-
}
128+
let mut px = 0.0;
129+
let mut py = 0.0;
130+
let mut pz = 0.0;
131+
for bi in bodies.iter() {
132+
px += bi.vx * bi.mass;
133+
py += bi.vy * bi.mass;
134+
pz += bi.vz * bi.mass;
145135
}
136+
let sun = &mut bodies[0];
137+
sun.vx = - px / SOLAR_MASS;
138+
sun.vy = - py / SOLAR_MASS;
139+
sun.vz = - pz / SOLAR_MASS;
146140
}
147141

148142
fn main() {
149-
let args = os::args();
150-
let args = if os::getenv("RUST_BENCH").is_some() {
151-
vec!("".to_owned(), "1000".to_owned())
152-
} else if args.len() <= 1u {
153-
vec!("".to_owned(), "1000".to_owned())
143+
let n = if std::os::getenv("RUST_BENCH").is_some() {
144+
5000000
154145
} else {
155-
args.move_iter().collect()
146+
std::os::args().as_slice().get(1)
147+
.and_then(|arg| from_str(*arg))
148+
.unwrap_or(1000)
156149
};
157-
158-
let n: i32 = from_str::<i32>(*args.get(1)).unwrap();
159150
let mut bodies = BODIES;
160151

161152
offset_momentum(&mut bodies);
162-
println!("{:.9f}", energy(&bodies) as f64);
153+
println!("{:.9f}", energy(&bodies));
163154

164155
advance(&mut bodies, 0.01, n);
165156

166-
println!("{:.9f}", energy(&bodies) as f64);
157+
println!("{:.9f}", energy(&bodies));
167158
}
168-

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