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/* The Great Computer Language Shootout | |
http://shootout.alioth.debian.org/ | |
contributed by Isaac Gouy */ | |
var PI = 3.141592653589793; | |
var SOLAR_MASS = 4 * PI * PI; | |
var DAYS_PER_YEAR = 365.24; | |
function Body(x,y,z,vx,vy,vz,mass){ | |
this.x = x; | |
this.y = y; | |
this.z = z; | |
this.vx = vx; | |
this.vy = vy; | |
this.vz = vz; | |
this.mass = mass; | |
} | |
Body.prototype.offsetMomentum = function(px,py,pz) { | |
this.vx = -px / SOLAR_MASS; | |
this.vy = -py / SOLAR_MASS; | |
this.vz = -pz / SOLAR_MASS; | |
return this; | |
} | |
function Jupiter(){ | |
return new 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 | |
); | |
} | |
function Saturn(){ | |
return new 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 | |
); | |
} | |
function Uranus(){ | |
return new 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 | |
); | |
} | |
function Neptune(){ | |
return new 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 | |
); | |
} | |
function Sun(){ | |
return new Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS); | |
} | |
function NBodySystem(bodies){ | |
log(typeof(bodies)); | |
this.bodies = bodies; | |
log(typeof(this.bodies)); | |
log(JSON.stringify(this.bodies)); | |
var px = 0.0; | |
var py = 0.0; | |
var pz = 0.0; | |
var size = this.bodies.length; | |
for (var i=0; i<size; i++){ | |
var b = this.bodies[i]; | |
var m = b.mass; | |
px += b.vx * m; | |
py += b.vy * m; | |
pz += b.vz * m; | |
} | |
this.bodies[0].offsetMomentum(px,py,pz); | |
} | |
NBodySystem.prototype.advance = function(dt){ | |
var dx, dy, dz, distance, mag; | |
var size = this.bodies.length; | |
for (var i=0; i<size; i++) { | |
var bodyi = this.bodies[i]; | |
for (var j=i+1; j<size; j++) { | |
var bodyj = this.bodies[j]; | |
dx = bodyi.x - bodyj.x; | |
dy = bodyi.y - bodyj.y; | |
dz = bodyi.z - bodyj.z; | |
distance = Math.sqrt(dx*dx + dy*dy + dz*dz); | |
mag = dt / (distance * distance * distance); | |
bodyi.vx -= dx * bodyj.mass * mag; | |
bodyi.vy -= dy * bodyj.mass * mag; | |
bodyi.vz -= dz * bodyj.mass * mag; | |
bodyj.vx += dx * bodyi.mass * mag; | |
bodyj.vy += dy * bodyi.mass * mag; | |
bodyj.vz += dz * bodyi.mass * mag; | |
} | |
} | |
for (var i=0; i<size; i++) { | |
var body = this.bodies[i]; | |
body.x += dt * body.vx; | |
body.y += dt * body.vy; | |
body.z += dt * body.vz; | |
} | |
} | |
NBodySystem.prototype.energy = function(){ | |
var dx, dy, dz, distance; | |
var e = 0.0; | |
var size = this.bodies.length; | |
for (var i=0; i<size; i++) { | |
var bodyi = this.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++) { | |
var bodyj = this.bodies[j]; | |
dx = bodyi.x - bodyj.x; | |
dy = bodyi.y - bodyj.y; | |
dz = bodyi.z - bodyj.z; | |
distance = Math.sqrt(dx*dx + dy*dy + dz*dz); | |
e -= (bodyi.mass * bodyj.mass) / distance; | |
} | |
} | |
return e; | |
} | |
var ret = 0; | |
for ( var n = 3; n <= 24; n *= 2 ) { | |
(function(){ | |
var bodies = new NBodySystem( Array( | |
Sun(),Jupiter(),Saturn(),Uranus(),Neptune() | |
)); | |
var max = n * 100; | |
ret += bodies.energy(); | |
for (var i=0; i<max; i++){ | |
bodies.advance(0.01); | |
} | |
ret += bodies.energy(); | |
})(); | |
} | |
var expected = -1.3524862408537381; | |
if (ret != expected) | |
throw "ERROR: bad result: expected " + expected + " but got " + ret; |
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