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anvaka/nbody_array.js

Created April 22, 2013 21:27
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nbody_array.js
/* The Computer Language Benchmarks Game
http://benchmarksgame.alioth.debian.org/
contributed by Isaac Gouy
Optimized by Roy Williams*/
/**
* @type {number}
*/
var PI = 3.141592653589793;
/**
* @type {number}
*/
var SOLAR_MASS = 4 * PI * PI;
/**
* @type {number}
*/
var DAYS_PER_YEAR = 365.24;
/**
* @param {number} x
* @param {number} y
* @param {number} z
* @param {number} vx
* @param {number} vy
* @param {number} vz
* @param {number} mass
* @constructor
*/
function Body(x,y,z,vx,vy,vz,mass,buffer,bodyIndex) {
this.storage_ = new Float64Array(
buffer, bodyIndex * Body.BYTES_SIZE, Body.NUM_FIELDS);
this.storage_[Body.X] = x;
this.storage_[Body.Y] = y;
this.storage_[Body.Z] = z;
this.storage_[Body.VX] = vx;
this.storage_[Body.VY] = vy;
this.storage_[Body.VZ] = vz;
this.storage_[Body.MASS] = mass;
}
/**
* @type {number}
* @const
*/
Body.NUM_FIELDS = 7;
/**
* @type {number}
* @const
*/
Body.BYTES_SIZE = Body.NUM_FIELDS * 8;
/**
* @type {number}
* @const
*/
Body.X = 0;
/**
* @type {number}
* @const
*/
Body.Y = 1;
/**
* @type {number}
* @const
*/
Body.Z = 2;
/**
* @type {number}
* @const
*/
Body.VX = 3;
/**
* @type {number}
* @const
*/
Body.VY = 4;
/**
* @type {number}
* @const
*/
Body.VZ = 5;
/**
* @type {number}
* @const
*/
Body.MASS = 6;
/**
* @param {number} px
* @param {number} py
* @param {number} pz
*/
Body.prototype.offsetMomentum = function(px,py,pz) {
this.storage_[Body.VX] = -px / SOLAR_MASS;
this.storage_[Body.VY] = -py / SOLAR_MASS;
this.storage_[Body.VZ] = -pz / SOLAR_MASS;
}
/**
* @return {Body}
*/
function Jupiter(buffer, bodyIndex){
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,
buffer, bodyIndex
);
}
/**
* @return {Body}
*/
function Saturn(buffer, bodyIndex){
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,
buffer, bodyIndex
);
}
/**
* @return {Body}
*/
function Uranus(buffer, bodyIndex){
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,
buffer, bodyIndex
);
}
/**
* @return {Body}
*/
function Neptune(buffer, bodyIndex){
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,
buffer, bodyIndex
);
}
/**
* @return {Body}
*/
function Sun(buffer, bodyIndex){
return new Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS, buffer, bodyIndex);
}
/**
* @param {Array.<Body>} bodies
* @constructor
*/
function NBodySystem(bodies){
/**
* @type {Array.<Body>}
*/
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.storage_[Body.MASS];
px += b.storage_[Body.VX] * m;
py += b.storage_[Body.VY] * m;
pz += b.storage_[Body.VZ] * m;
}
this.bodies[0].offsetMomentum(px,py,pz);
}
/**
* @param {number} dt
*/
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];
var imass = bodyi.storage_[Body.MASS]
for (var j=i+1; j<size; j++) {
var bodyj = this.bodies[j];
var jmass = bodyj.storage_[Body.MASS];
dx = bodyi.storage_[Body.X] - bodyj.storage_[Body.X];
dy = bodyi.storage_[Body.Y] - bodyj.storage_[Body.Y];
dz = bodyi.storage_[Body.Z] - bodyj.storage_[Body.Z];
distance = Math.sqrt(dx*dx + dy*dy + dz*dz);
mag = dt / (distance * distance * distance);
bodyi.storage_[Body.VX] -= dx * jmass * mag;
bodyi.storage_[Body.VY] -= dy * jmass * mag;
bodyi.storage_[Body.VZ] -= dz * jmass * mag;
bodyj.storage_[Body.VX] += dx * imass * mag;
bodyj.storage_[Body.VY] += dy * imass * mag;
bodyj.storage_[Body.VZ] += dz * imass * mag;
}
bodyi.storage_[Body.X] += dt * bodyi.storage_[Body.VX];
bodyi.storage_[Body.Y] += dt * bodyi.storage_[Body.VY];
bodyi.storage_[Body.Z] += dt * bodyi.storage_[Body.VZ];
}
}
/**
* @return {number}
*/
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.storage_[Body.MASS] *
( bodyi.storage_[Body.VX] * bodyi.storage_[Body.VX]
+ bodyi.storage_[Body.VY] * bodyi.storage_[Body.VY]
+ bodyi.storage_[Body.VZ] * bodyi.storage_[Body.VZ] );
for (var j=i+1; j<size; j++) {
var bodyj = this.bodies[j];
dx = bodyi.storage_[Body.X] - bodyj.storage_[Body.X];
dy = bodyi.storage_[Body.Y] - bodyj.storage_[Body.Y];
dz = bodyi.storage_[Body.Z] - bodyj.storage_[Body.Z];
distance = Math.sqrt(dx*dx + dy*dy + dz*dz);
e -= (bodyi.storage_[Body.MASS] *
bodyj.storage_[Body.MASS]) / distance;
}
}
return e;
}
/**
* @type {number}
*/
n = arguments[0];
/**
* @param {number} n
*/
runTest = function(n) {
var bodyBuffer = new ArrayBuffer(Body.BYTES_SIZE * 5);
var bodies = new NBodySystem( Array(
Sun(bodyBuffer, 0),Jupiter(bodyBuffer, 1),
Saturn(bodyBuffer, 2),Uranus(bodyBuffer, 3),Neptune(bodyBuffer, 4)
));
print(bodies.energy().toFixed(9));
for (var i=0; i<n; i++){ bodies.advance(0.01); }
print(bodies.energy().toFixed(9));
}
runTest(n);
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