n-body Dart #6 program

/* The Computer Language Benchmarks Game
   https://salsa.debian.org/benchmarksgame-team/benchmarksgame/

   transliterated from Andrey Filatkin's Node #6 program 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 = 0, y = 0, z = 0, vx = 0, vy = 0, vz = 0, mass = 0;
  Body(this.x, this.y, this.z, this.vx, this.vy, this.vz, this.mass);
}

Body Jupiter() {
  return 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);
}

Body Saturn() {
  return 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);
}

Body Uranus() {
  return 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);
}

Body Neptune() {
  return 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);
}

Body Sun() {
  return Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS);
}

final bodies = [Sun(), Jupiter(), Saturn(), Uranus(), Neptune()];

void offsetMomentum() {
  var px = 0.0;
  var py = 0.0;
  var pz = 0.0;
  final size = bodies.length;
  for (var i = 0; i < size; i++) {
    final body = bodies[i];
    final mass = body.mass;
    px += body.vx * mass;
    py += body.vy * mass;
    pz += body.vz * mass;
  }

  final body = bodies[0];
  body.vx = -px / SOLAR_MASS;
  body.vy = -py / SOLAR_MASS;
  body.vz = -pz / SOLAR_MASS;
}

void advance(double dt) {
  final size = bodies.length;

  for (var i = 0; i < size; i++) {
    final bodyi = bodies[i];
    var vxi = bodyi.vx;
    var vyi = bodyi.vy;
    var vzi = bodyi.vz;
    for (var j = i + 1; j < size; j++) {
      final bodyj = bodies[j];
      final dx = bodyi.x - bodyj.x;
      final dy = bodyi.y - bodyj.y;
      final dz = bodyi.z - bodyj.z;

      final d2 = dx * dx + dy * dy + dz * dz;
      final mag = dt / (d2 * Math.sqrt(d2));

      final massj = bodyj.mass;
      vxi -= dx * massj * mag;
      vyi -= dy * massj * mag;
      vzi -= dz * massj * mag;

      final massi = bodyi.mass;
      bodyj.vx += dx * massi * mag;
      bodyj.vy += dy * massi * mag;
      bodyj.vz += dz * massi * mag;
    }
    bodyi.vx = vxi;
    bodyi.vy = vyi;
    bodyi.vz = vzi;
  }

  for (var i = 0; i < size; i++) {
    final body = bodies[i];
    body.x += dt * body.vx;
    body.y += dt * body.vy;
    body.z += dt * body.vz;
  }
}

double energy() {
  var e = 0.0;
  final size = bodies.length;

  for (var i = 0; i < size; i++) {
    final bodyi = bodies[i];

    e += 0.5 *
        bodyi.mass *
        (bodyi.vx * bodyi.vx + bodyi.vy * bodyi.vy + bodyi.vz * bodyi.vz);

    for (var j = i + 1; j < size; j++) {
      final bodyj = bodies[j];
      final dx = bodyi.x - bodyj.x;
      final dy = bodyi.y - bodyj.y;
      final dz = bodyi.z - bodyj.z;

      final distance = Math.sqrt(dx * dx + dy * dy + dz * dz);
      e -= (bodyi.mass * bodyj.mass) / distance;
    }
  }
  return e;
}

void main(List<String> args) {
  final n = (args.length > 0) ? int.parse(args[0]) : 1000;

  offsetMomentum();
  print(energy().toStringAsFixed(9));
  for (int i = 0; i < n; i++) {
    advance(0.01);
  }
  print(energy().toStringAsFixed(9));
}
    

NOTES:
64-bit Ubuntu quad core
Dart SDK version: 3.5.4 (stable)
Wed Oct 16 16:18:51 2024



 Wed, 23 Oct 2024 20:18:08 GMT

MAKE:
/opt/src/dart-sdk/bin/dart analyze 
Analyzing tmp...
No issues found!

/opt/src/dart-sdk/bin/dart compile exe nbody.dartexe-6.dartexe -o nbody.dartexe-6.dartexe_run
Generated: /home/dunham/all-benchmarksgame/benchmarksgame_i53330/nbody/tmp/nbody.dartexe-6.dartexe_run

4.68s to complete and log all make actions

COMMAND LINE:
 ./nbody.dartexe-6.dartexe_run 50000000

PROGRAM OUTPUT:
-0.169075164
-0.169059907