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/* The Great Computer Language Shootout
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){
this.bodies = 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;
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();
})();
}
assertEq(ret, -0.16906933525822856)