source code
/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
Naive transliteration from Michael Ferguson's Chapel program
contributed by Isaac Gouy
*/
import 'dart:math' as Math;
const SOLAR_MASS = 4 * Math.pi * Math.pi;
const DAYS_PER_YEAR = 365.24;
class Body {
double x, y, z, vx, vy, vz, mass;
Body(this.x, this.y, this.z, this.vx, this.vy, this.vz, this.mass);
}
void offsetMomentum(List<Body> bodies) {
var px = 0.0, py = 0.0, pz = 0.0;
for (final b in bodies) {
final mass = b.mass;
px += b.vx * mass;
py += b.vy * mass;
pz += b.vz * mass;
}
final b = bodies[0];
b.vx = -px / SOLAR_MASS;
b.vy = -py / SOLAR_MASS;
b.vz = -pz / SOLAR_MASS;
}
double energy(List<Body> bodies) {
var e = 0.0;
final numBodies = bodies.length;
for (var i = 0; i < numBodies; i++) {
final b = bodies[i];
final sq = b.vx * b.vx + b.vy * b.vy + b.vz * b.vz;
e += 0.5 * b.mass * sq;
for (var j = i + 1; j < numBodies; j++) {
final bodyj = bodies[j];
final dx = b.x - bodyj.x;
final dy = b.y - bodyj.y;
final dz = b.z - bodyj.z;
final sq = dx * dx + dy * dy + dz * dz;
final distance = Math.sqrt(dx * dx + dy * dy + dz * dz);
e -= (b.mass * bodyj.mass) / Math.sqrt(sq);
}
}
return e;
}
void advance(List<Body> bodies, double dt) {
final numBodies = bodies.length;
for (var i = 0; i < numBodies; i++) {
for (var j = i + 1; j < numBodies; j++) {
final dx = bodies[i].x - bodies[j].x;
final dy = bodies[i].y - bodies[j].y;
final dz = bodies[i].z - bodies[j].z;
final sq = dx * dx + dy * dy + dz * dz;
final mag = dt / (sq * Math.sqrt(sq));
final mj = bodies[j].mass * mag;
bodies[i].vx -= dx * mj;
bodies[i].vy -= dy * mj;
bodies[i].vz -= dz * mj;
final mi = bodies[i].mass * mag;
bodies[j].vx += dx * mi;
bodies[j].vy += dy * mi;
bodies[j].vz += dz * mi;
}
}
for (final b in bodies) {
b.x += b.vx * dt;
b.y += b.vy * dt;
b.z += b.vz * dt;
}
}
void main(List<String> args) {
final n = (args.length > 0) ? int.parse(args[0]) : 1000;
final bodies = [
// sun
Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS),
// jupiter
Body(
4.84143144246472090e+00,
-1.16032004402742839e+00,
-1.03622044471123109e-01,
1.66007664274403694e-03 * DAYS_PER_YEAR,
7.69901118419740425e-03 * DAYS_PER_YEAR,
-6.90460016972063023e-05 * DAYS_PER_YEAR,
9.54791938424326609e-04 * SOLAR_MASS
),
// saturn
Body(
8.34336671824457987e+00,
4.12479856412430479e+00,
-4.03523417114321381e-01,
-2.76742510726862411e-03 * DAYS_PER_YEAR,
4.99852801234917238e-03 * DAYS_PER_YEAR,
2.30417297573763929e-05 * DAYS_PER_YEAR,
2.85885980666130812e-04 * SOLAR_MASS
),
// uranus
Body(
1.28943695621391310e+01,
-1.51111514016986312e+01,
-2.23307578892655734e-01,
2.96460137564761618e-03 * DAYS_PER_YEAR,
2.37847173959480950e-03 * DAYS_PER_YEAR,
-2.96589568540237556e-05 * DAYS_PER_YEAR,
4.36624404335156298e-05 * SOLAR_MASS
),
// neptune
Body(
1.53796971148509165e+01,
-2.59193146099879641e+01,
1.79258772950371181e-01,
2.68067772490389322e-03 * DAYS_PER_YEAR,
1.62824170038242295e-03 * DAYS_PER_YEAR,
-9.51592254519715870e-05 * DAYS_PER_YEAR,
5.15138902046611451e-05 * SOLAR_MASS
),
];
offsetMomentum(bodies);
print(energy(bodies).toStringAsFixed(9));
for (var i = 0; i < n; i++) {
advance(bodies,0.01);
}
print(energy(bodies).toStringAsFixed(9));
}