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access-nbody.as
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access-nbody.as
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/* The Great Computer Language Shootout
http://shootout.alioth.debian.org/
contributed by Isaac Gouy */
package {
public class Body {
public static var PI:Number = 3.141592653589793;
public static var SOLAR_MASS:Number = 4 * PI * PI;
public static var DAYS_PER_YEAR:Number = 365.24;
public var x:Number, y:Number, z:Number, vx:Number, vy:Number, vz:Number, mass:Number;
public function Body(x:Number, y:Number, z:Number, vx:Number, vy:Number, vz:Number, mass:Number):void{
this.x = x;
this.y = y;
this.z = z;
this.vx = vx;
this.vy = vy;
this.vz = vz;
this.mass = mass;
}
public static function Jupiter():Body {
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
);
}
public static function Saturn():Body {
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
);
}
public static function Uranus():Body {
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
);
}
public static function Neptune():Body {
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
);
}
public static function Sun():Body {
return new Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS);
}
public function offsetMomentum (px:Number, py:Number, pz:Number):Body {
this.vx = -px / SOLAR_MASS;
this.vy = -py / SOLAR_MASS;
this.vz = -pz / SOLAR_MASS;
return this;
}
}
public class NBodySystem {
public var bodies:Array = new Array(5);
public function NBodySystem():void {
bodies[0] = Body.Sun();
bodies[1] = Body.Jupiter();
bodies[2] = Body.Saturn();
bodies[3] = Body.Uranus();
bodies[4] = Body.Neptune();
var px:Number = 0.0;
var py:Number = 0.0;
var pz:Number = 0.0;
for(var i:int = 0; i < bodies.length; ++i) {
px += bodies[i].vx * bodies[i].mass;
py += bodies[i].vy * bodies[i].mass;
pz += bodies[i].vz * bodies[i].mass;
}
bodies[0].offsetMomentum(px,py,pz);
}
public function advance(dt:Number):void {
var dx:Number, dy:Number, dz:Number, distance:Number, mag:Number;
var size:Number = this.bodies.length;
for (var i:int=0; i<size; i++) {
var bodyi:Body = this.bodies[i];
for (var j:int=i+1; j<size; j++) {
var bodyj:Body = 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:int=0; i<size; i++) {
var body:Body = this.bodies[i];
body.x += dt * body.vx;
body.y += dt * body.vy;
body.z += dt * body.vz;
}
}
public function energy():Number {
var dx:Number, dy:Number, dz:Number, distance:Number;
var e:Number = 0.0;
var size:Number = this.bodies.length;
for (var i:int=0; i<size; i++) {
var bodyi:Body = 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:Body = 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;
}
}
function runAccessNbody():Number {
var res:Number;
for ( var n:int = 3; n <= 24 * 4 * 128 * 2; n *= 2 ) {
var bodies:NBodySystem = new NBodySystem();
var max:Number = n * 100;
res = bodies.energy();
for (var i=0; i<max; i++){
bodies.advance(0.01);
}
res = bodies.energy();
print(""+n+"="+res);
}
return res;
}
var start:Number = new Date();
var res:Number = runAccessNbody();
var totaltime:Number = new Date() - start;
if (res-(-0.1690525098446868)<0.00001)
print("PASSED res="+res);
else
print("FAILED nbody result expecting -0.1690525098446868 got "+res);
/*
if (res-(-0.1690693)<0.00001)
print("metric time "+totaltime);
else
print("error nbody result expecting -0.1690693 got "+res);
*/
}