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|
// xfail-boot
// based on:
// http://shootout.alioth.debian.org/u32/benchmark.php?test=nbody&lang=java
native "llvm" mod llvm {
fn sqrt(float n) -> float = "sqrt.f64";
}
fn main() {
let vec[int] inputs = vec(
50000,
500000
//
// Leave these commented out to
// finish in a reasonable time
// during 'make check' under valgrind
// 5000000
// 50000000
);
let vec[Body::props] bodies = NBodySystem::MakeNBodySystem();
for (int n in inputs) {
log NBodySystem::energy(bodies);
let int i = 0;
while (i < n) {
NBodySystem::advance(bodies, 0.01);
i += 1;
}
log NBodySystem::energy(bodies);
}
}
// Body::props is a record of floats, so
// vec[Body::props] is a vector of records of floats
mod NBodySystem {
fn MakeNBodySystem() -> vec[Body::props] {
let vec[Body::props] bodies = vec(
// these each return a Body::props
Body::sun(),
Body::jupiter(),
Body::saturn(),
Body::uranus(),
Body::neptune());
let float px = 0.0;
let float py = 0.0;
let float pz = 0.0;
let int i = 0;
while (i < 5) {
px += bodies.(i).vx * bodies.(i).mass;
py += bodies.(i).vy * bodies.(i).mass;
pz += bodies.(i).vz * bodies.(i).mass;
i += 1;
}
// side-effecting
Body::offsetMomentum(bodies.(0), px, py, pz);
ret bodies;
}
fn advance(vec[Body::props] bodies, float dt) -> () {
let int i = 0;
while (i < 5) {
let int j = i+1;
while (j < 5) {
advance_one(bodies.(i), bodies.(j), dt);
j += 1;
}
i += 1;
}
i = 0;
while (i < 5) {
move(bodies.(i), dt);
i += 1;
}
}
fn advance_one(&Body::props bi, &Body::props bj, float dt) {
let float dx = bi.x - bj.x;
let float dy = bi.y - bj.y;
let float dz = bi.z - bj.z;
let float dSquared = dx * dx + dy * dy + dz * dz;
let float distance = llvm::sqrt(dSquared);
let float mag = dt / (dSquared * distance);
bi.vx -= dx * bj.mass * mag;
bi.vy -= dy * bj.mass * mag;
bi.vz -= dz * bj.mass * mag;
bj.vx += dx * bi.mass * mag;
bj.vy += dy * bi.mass * mag;
bj.vz += dz * bi.mass * mag;
}
fn move(&Body::props b, float dt) {
b.x += dt * b.vx;
b.y += dt * b.vy;
b.z += dt * b.vz;
}
fn energy(vec[Body::props] bodies) -> float {
let float dx;
let float dy;
let float dz;
let float distance;
let float e = 0.0;
let int i = 0;
while (i < 5) {
e += 0.5 * bodies.(i).mass *
( bodies.(i).vx * bodies.(i).vx
+ bodies.(i).vy * bodies.(i).vy
+ bodies.(i).vz * bodies.(i).vz );
let int j = i+1;
while (j < 5) {
dx = bodies.(i).x - bodies.(j).x;
dy = bodies.(i).y - bodies.(j).y;
dz = bodies.(i).z - bodies.(j).z;
distance = llvm::sqrt(dx*dx + dy*dy + dz*dz);
e -= (bodies.(i).mass * bodies.(j).mass) / distance;
j += 1;
}
i += 1;
}
ret e;
}
}
mod Body {
const float PI = 3.141592653589793;
const float SOLAR_MASS = 39.478417604357432; // was 4 * PI * PI originally
const float DAYS_PER_YEAR = 365.24;
type props = rec(mutable float x,
mutable float y,
mutable float z,
mutable float vx,
mutable float vy,
mutable float vz,
float mass);
fn jupiter() -> Body::props {
ret rec(
mutable x = 4.84143144246472090e+00,
mutable y = -1.16032004402742839e+00,
mutable z = -1.03622044471123109e-01,
mutable vx = 1.66007664274403694e-03 * DAYS_PER_YEAR,
mutable vy = 7.69901118419740425e-03 * DAYS_PER_YEAR,
mutable vz = -6.90460016972063023e-05 * DAYS_PER_YEAR,
mass = 9.54791938424326609e-04 * SOLAR_MASS
);
}
fn saturn() -> Body::props {
ret rec(
mutable x = 8.34336671824457987e+00,
mutable y = 4.12479856412430479e+00,
mutable z = -4.03523417114321381e-01,
mutable vx = -2.76742510726862411e-03 * DAYS_PER_YEAR,
mutable vy = 4.99852801234917238e-03 * DAYS_PER_YEAR,
mutable vz = 2.30417297573763929e-05 * DAYS_PER_YEAR,
mass = 2.85885980666130812e-04 * SOLAR_MASS
);
}
fn uranus() -> Body::props {
ret rec(
mutable x = 1.28943695621391310e+01,
mutable y = -1.51111514016986312e+01,
mutable z = -2.23307578892655734e-01,
mutable vx = 2.96460137564761618e-03 * DAYS_PER_YEAR,
mutable vy = 2.37847173959480950e-03 * DAYS_PER_YEAR,
mutable vz = -2.96589568540237556e-05 * DAYS_PER_YEAR,
mass = 4.36624404335156298e-05 * SOLAR_MASS
);
}
fn neptune() -> Body::props {
ret rec(
mutable x = 1.53796971148509165e+01,
mutable y = -2.59193146099879641e+01,
mutable z = 1.79258772950371181e-01,
mutable vx = 2.68067772490389322e-03 * DAYS_PER_YEAR,
mutable vy = 1.62824170038242295e-03 * DAYS_PER_YEAR,
mutable vz = -9.51592254519715870e-05 * DAYS_PER_YEAR,
mass = 5.15138902046611451e-05 * SOLAR_MASS
);
}
fn sun() -> Body::props {
ret rec(
mutable x = 0.0,
mutable y = 0.0,
mutable z = 0.0,
mutable vx = 0.0,
mutable vy = 0.0,
mutable vz = 0.0,
mass = SOLAR_MASS
);
}
fn offsetMomentum(&Body::props props,
float px,
float py,
float pz) -> () {
props.vx = -px / SOLAR_MASS;
props.vy = -py / SOLAR_MASS;
props.vz = -pz / SOLAR_MASS;
}
}
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