js/src/t/access-nbody.js

   1 /* The Great Computer Language Shootout
   2    http://shootout.alioth.debian.org/
   3    contributed by Isaac Gouy */
   4
   5 var PI = 3.141592653589793;
   6 var SOLAR_MASS = 4 * PI * PI;
   7 var DAYS_PER_YEAR = 365.24;
   8
   9 function Body(x,y,z,vx,vy,vz,mass){
  10    this.x = x;
  11    this.y = y;
  12    this.z = z;
  13    this.vx = vx;
  14    this.vy = vy;
  15    this.vz = vz;
  16    this.mass = mass;
  17 }
  18
  19 Body.prototype.offsetMomentum = function(px,py,pz) {
  20    this.vx = -px / SOLAR_MASS;
  21    this.vy = -py / SOLAR_MASS;
  22    this.vz = -pz / SOLAR_MASS;
  23    return this;
  24 }
  25
  26 function Jupiter(){
  27    return new Body(
  28       4.84143144246472090e+00,
  29       -1.16032004402742839e+00,
  30       -1.03622044471123109e-01,
  31       1.66007664274403694e-03 * DAYS_PER_YEAR,
  32       7.69901118419740425e-03 * DAYS_PER_YEAR,
  33       -6.90460016972063023e-05 * DAYS_PER_YEAR,
  34       9.54791938424326609e-04 * SOLAR_MASS
  35    );
  36 }
  37
  38 function Saturn(){
  39    return new Body(
  40       8.34336671824457987e+00,
  41       4.12479856412430479e+00,
  42       -4.03523417114321381e-01,
  43       -2.76742510726862411e-03 * DAYS_PER_YEAR,
  44       4.99852801234917238e-03 * DAYS_PER_YEAR,
  45       2.30417297573763929e-05 * DAYS_PER_YEAR,
  46       2.85885980666130812e-04 * SOLAR_MASS
  47    );
  48 }
  49
  50 function Uranus(){
  51    return new Body(
  52       1.28943695621391310e+01,
  53       -1.51111514016986312e+01,
  54       -2.23307578892655734e-01,
  55       2.96460137564761618e-03 * DAYS_PER_YEAR,
  56       2.37847173959480950e-03 * DAYS_PER_YEAR,
  57       -2.96589568540237556e-05 * DAYS_PER_YEAR,
  58       4.36624404335156298e-05 * SOLAR_MASS
  59    );
  60 }
  61
  62 function Neptune(){
  63    return new Body(
  64       1.53796971148509165e+01,
  65       -2.59193146099879641e+01,
  66       1.79258772950371181e-01,
  67       2.68067772490389322e-03 * DAYS_PER_YEAR,
  68       1.62824170038242295e-03 * DAYS_PER_YEAR,
  69       -9.51592254519715870e-05 * DAYS_PER_YEAR,
  70       5.15138902046611451e-05 * SOLAR_MASS
  71    );
  72 }
  73
  74 function Sun(){
  75    return new Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS);
  76 }
  77
  78
  79 function NBodySystem(bodies){
  80    this.bodies = bodies;
  81    var px = 0.0;
  82    var py = 0.0;
  83    var pz = 0.0;
  84    var size = this.bodies.length;
  85    for (var i=0; i<size; i++){
  86       var b = this.bodies[i];
  87       var m = b.mass;
  88       px += b.vx * m;
  89       py += b.vy * m;
  90       pz += b.vz * m;
  91    }
  92    this.bodies[0].offsetMomentum(px,py,pz);
  93 }
  94
  95 NBodySystem.prototype.advance = function(dt){
  96    var dx, dy, dz, distance, mag;
  97    var size = this.bodies.length;
  98
  99    for (var i=0; i<size; i++) {
 100       var bodyi = this.bodies[i];
 101       for (var j=i+1; j<size; j++) {
 102          var bodyj = this.bodies[j];
 103          dx = bodyi.x - bodyj.x;
 104          dy = bodyi.y - bodyj.y;
 105          dz = bodyi.z - bodyj.z;
 106
 107          distance = Math.sqrt(dx*dx + dy*dy + dz*dz);
 108          mag = dt / (distance * distance * distance);
 109
 110          bodyi.vx -= dx * bodyj.mass * mag;
 111          bodyi.vy -= dy * bodyj.mass * mag;
 112          bodyi.vz -= dz * bodyj.mass * mag;
 113
 114          bodyj.vx += dx * bodyi.mass * mag;
 115          bodyj.vy += dy * bodyi.mass * mag;
 116          bodyj.vz += dz * bodyi.mass * mag;
 117       }
 118    }
 119
 120    for (var i=0; i<size; i++) {
 121       var body = this.bodies[i];
 122       body.x += dt * body.vx;
 123       body.y += dt * body.vy;
 124       body.z += dt * body.vz;
 125    }
 126 }
 127
 128 NBodySystem.prototype.energy = function(){
 129    var dx, dy, dz, distance;
 130    var e = 0.0;
 131    var size = this.bodies.length;
 132
 133    for (var i=0; i<size; i++) {
 134       var bodyi = this.bodies[i];
 135
 136       e += 0.5 * bodyi.mass *
 137          ( bodyi.vx * bodyi.vx
 138          + bodyi.vy * bodyi.vy
 139          + bodyi.vz * bodyi.vz );
 140
 141       for (var j=i+1; j<size; j++) {
 142          var bodyj = this.bodies[j];
 143          dx = bodyi.x - bodyj.x;
 144          dy = bodyi.y - bodyj.y;
 145          dz = bodyi.z - bodyj.z;
 146
 147          distance = Math.sqrt(dx*dx + dy*dy + dz*dz);
 148          e -= (bodyi.mass * bodyj.mass) / distance;
 149       }
 150    }
 151    return e;
 152 }
 153
 154 var ret;
 155
 156 for ( var n = 3; n <= 24; n *= 2 ) {
 157     (function(){
 158         var bodies = new NBodySystem( Array(
 159            Sun(),Jupiter(),Saturn(),Uranus(),Neptune()
 160         ));
 161         var max = n * 100;
 162
 163         ret = bodies.energy();
 164         for (var i=0; i<max; i++){
 165             bodies.advance(0.01);
 166         }
 167         ret = bodies.energy();
 168     })();
 169 }