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1 /* The Great Computer Language Shootout |
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2 http://shootout.alioth.debian.org/ |
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3 contributed by Isaac Gouy */ |
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4 |
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5 var PI = 3.141592653589793; |
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6 var SOLAR_MASS = 4 * PI * PI; |
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7 var DAYS_PER_YEAR = 365.24; |
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8 |
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9 function Body(x,y,z,vx,vy,vz,mass){ |
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10 this.x = x; |
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11 this.y = y; |
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12 this.z = z; |
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13 this.vx = vx; |
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14 this.vy = vy; |
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15 this.vz = vz; |
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16 this.mass = mass; |
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17 } |
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18 |
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19 Body.prototype.offsetMomentum = function(px,py,pz) { |
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20 this.vx = -px / SOLAR_MASS; |
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21 this.vy = -py / SOLAR_MASS; |
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22 this.vz = -pz / SOLAR_MASS; |
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23 return this; |
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24 } |
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25 |
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26 function Jupiter(){ |
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27 return new Body( |
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28 4.84143144246472090e+00, |
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29 -1.16032004402742839e+00, |
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30 -1.03622044471123109e-01, |
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31 1.66007664274403694e-03 * DAYS_PER_YEAR, |
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32 7.69901118419740425e-03 * DAYS_PER_YEAR, |
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33 -6.90460016972063023e-05 * DAYS_PER_YEAR, |
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34 9.54791938424326609e-04 * SOLAR_MASS |
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35 ); |
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36 } |
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37 |
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38 function Saturn(){ |
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39 return new Body( |
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40 8.34336671824457987e+00, |
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41 4.12479856412430479e+00, |
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42 -4.03523417114321381e-01, |
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43 -2.76742510726862411e-03 * DAYS_PER_YEAR, |
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44 4.99852801234917238e-03 * DAYS_PER_YEAR, |
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45 2.30417297573763929e-05 * DAYS_PER_YEAR, |
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46 2.85885980666130812e-04 * SOLAR_MASS |
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47 ); |
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48 } |
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49 |
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50 function Uranus(){ |
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51 return new Body( |
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52 1.28943695621391310e+01, |
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53 -1.51111514016986312e+01, |
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54 -2.23307578892655734e-01, |
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55 2.96460137564761618e-03 * DAYS_PER_YEAR, |
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56 2.37847173959480950e-03 * DAYS_PER_YEAR, |
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57 -2.96589568540237556e-05 * DAYS_PER_YEAR, |
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58 4.36624404335156298e-05 * SOLAR_MASS |
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59 ); |
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60 } |
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61 |
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62 function Neptune(){ |
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63 return new Body( |
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64 1.53796971148509165e+01, |
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65 -2.59193146099879641e+01, |
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66 1.79258772950371181e-01, |
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67 2.68067772490389322e-03 * DAYS_PER_YEAR, |
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68 1.62824170038242295e-03 * DAYS_PER_YEAR, |
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69 -9.51592254519715870e-05 * DAYS_PER_YEAR, |
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70 5.15138902046611451e-05 * SOLAR_MASS |
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71 ); |
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72 } |
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73 |
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74 function Sun(){ |
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75 return new Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS); |
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76 } |
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77 |
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78 |
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79 function NBodySystem(bodies){ |
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80 this.bodies = bodies; |
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81 var px = 0.0; |
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82 var py = 0.0; |
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83 var pz = 0.0; |
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84 var size = this.bodies.length; |
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85 for (var i=0; i<size; i++){ |
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86 var b = this.bodies[i]; |
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87 var m = b.mass; |
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88 px += b.vx * m; |
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89 py += b.vy * m; |
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90 pz += b.vz * m; |
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91 } |
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92 this.bodies[0].offsetMomentum(px,py,pz); |
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93 } |
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94 |
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95 NBodySystem.prototype.advance = function(dt){ |
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96 var dx, dy, dz, distance, mag; |
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97 var size = this.bodies.length; |
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98 |
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99 for (var i=0; i<size; i++) { |
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100 var bodyi = this.bodies[i]; |
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101 for (var j=i+1; j<size; j++) { |
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102 var bodyj = this.bodies[j]; |
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103 dx = bodyi.x - bodyj.x; |
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104 dy = bodyi.y - bodyj.y; |
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105 dz = bodyi.z - bodyj.z; |
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106 |
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107 distance = Math.sqrt(dx*dx + dy*dy + dz*dz); |
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108 mag = dt / (distance * distance * distance); |
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109 |
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110 bodyi.vx -= dx * bodyj.mass * mag; |
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111 bodyi.vy -= dy * bodyj.mass * mag; |
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112 bodyi.vz -= dz * bodyj.mass * mag; |
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113 |
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114 bodyj.vx += dx * bodyi.mass * mag; |
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115 bodyj.vy += dy * bodyi.mass * mag; |
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116 bodyj.vz += dz * bodyi.mass * mag; |
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117 } |
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118 } |
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119 |
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120 for (var i=0; i<size; i++) { |
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121 var body = this.bodies[i]; |
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122 body.x += dt * body.vx; |
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123 body.y += dt * body.vy; |
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124 body.z += dt * body.vz; |
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125 } |
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126 } |
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127 |
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128 NBodySystem.prototype.energy = function(){ |
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129 var dx, dy, dz, distance; |
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130 var e = 0.0; |
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131 var size = this.bodies.length; |
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132 |
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133 for (var i=0; i<size; i++) { |
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134 var bodyi = this.bodies[i]; |
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135 |
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136 e += 0.5 * bodyi.mass * |
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137 ( bodyi.vx * bodyi.vx |
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138 + bodyi.vy * bodyi.vy |
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139 + bodyi.vz * bodyi.vz ); |
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140 |
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141 for (var j=i+1; j<size; j++) { |
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142 var bodyj = this.bodies[j]; |
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143 dx = bodyi.x - bodyj.x; |
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144 dy = bodyi.y - bodyj.y; |
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145 dz = bodyi.z - bodyj.z; |
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146 |
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147 distance = Math.sqrt(dx*dx + dy*dy + dz*dz); |
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148 e -= (bodyi.mass * bodyj.mass) / distance; |
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149 } |
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150 } |
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151 return e; |
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152 } |
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153 |
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154 var ret; |
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155 |
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156 for ( var n = 3; n <= 24; n *= 2 ) { |
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157 (function(){ |
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158 var bodies = new NBodySystem( Array( |
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159 Sun(),Jupiter(),Saturn(),Uranus(),Neptune() |
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160 )); |
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161 var max = n * 100; |
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162 |
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163 ret = bodies.energy(); |
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164 for (var i=0; i<max; i++){ |
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165 bodies.advance(0.01); |
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166 } |
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167 ret = bodies.energy(); |
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168 })(); |
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169 } |
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170 |
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171 assertEq(ret, -0.16906933525822856) |