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 } 170
