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/*
* Copyright (C) 2015 Linaro Limited. Ported to Java from:
* https://github.com/WebKit/webkit/blob/master/PerformanceTests/SunSpider/tests/sunspider-1.0.2/access-nbody.js
*
* Description: N-body simulation of a galaxy composed out of a four planets and the sun.
* Main Focus: Floating-point operations.
*
*/
/* The Great Computer Language Shootout
http://shootout.alioth.debian.org/
contributed by Isaac Gouy */
// http://benchmarksgame.alioth.debian.org/license.html (BSD 3-clause license)
// See NOTICE file for license.
package benchmarks.math;
import java.lang.Math;
import java.lang.System;
public class AccessNBody {
private static final double ACCESS_NBODY_EXPECTED = 1.4677045000258846;
private static final double DAYS_PER_YEAR = 365.24;
private static final double SOLAR_MASS = 4 * Math.PI * Math.PI;
private class Body {
public double x;
public double y;
public double z;
public double vx;
public double vy;
public double vz;
public double mass;
Body(double x, double y, double z, double vx, double vy, double vz, double mass) {
this.x = x;
this.y = y;
this.z = z;
this.vx = vx;
this.vy = vy;
this.vz = vz;
this.mass = mass;
}
void offsetMomentum(double px, double py, double pz) {
this.vx = -px / SOLAR_MASS;
this.vy = -py / SOLAR_MASS;
this.vz = -pz / SOLAR_MASS;
}
}
private class NBodySystem {
private Body[] bodies;
private double px;
private double py;
private double pz;
NBodySystem(Body[] bodies) {
this.bodies = bodies;
for (int i = 0; i < bodies.length; i++) {
Body currentBody = this.bodies[i];
double mass = currentBody.mass;
px += currentBody.vx * mass;
py += currentBody.vy * mass;
pz += currentBody.vz * mass;
}
this.bodies[0].offsetMomentum(px, py, pz);
}
void advance(double dt) {
double dx;
double dy;
double dz;
double distance;
double mag;
for (int i = 0; i < bodies.length; i++) {
Body bodyI = this.bodies[i];
for (int j = i + 1; j < bodies.length; j++) {
Body 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 (int i = 0; i < bodies.length; i++) {
Body body = this.bodies[i];
body.x += dt * body.vx;
body.y += dt * body.vy;
body.z += dt * body.vz;
}
}
double energy() {
double dx;
double dy;
double dz;
double distance;
double e = 0.0;
for (int i = 0; i < bodies.length; i++) {
Body bodyI = this.bodies[i];
e += 0.5 * bodyI.mass
* (bodyI.vx * bodyI.vx + bodyI.vy * bodyI.vy + bodyI.vz * bodyI.vz);
for (int j = i + 1; j < bodies.length; j++) {
Body bodyJ = this.bodies[j];
dx = bodyI.x - bodyJ.x;
dy = bodyI.y - bodyJ.y;
dz = bodyJ.z - bodyJ.z;
distance = Math.sqrt(dx * dx + dy * dy + dz * dz);
e -= (bodyI.mass * bodyJ.mass) / distance;
}
}
return e;
}
}
private Body 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);
}
private Body 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);
}
private Body 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);
}
private Body 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);
}
private Body sun() {
return new Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
}
private double simulateGalaxy() {
double output = 0.0;
Body[] bodies = { sun(), jupiter(), saturn(), uranus(), neptune() };
NBodySystem galaxy = new NBodySystem(bodies);
for (int i = 3; i <= 24; i *= 2) {
output += galaxy.energy();
for (int j = 0; j < i * 100; j++) {
galaxy.advance(0.01);
}
output += galaxy.energy();
}
return output;
}
public void timeAccessNBody(int iters) {
for (int i = 0; i < iters; i++) {
simulateGalaxy();
}
}
public boolean verify() {
final double output = simulateGalaxy();
return output == ACCESS_NBODY_EXPECTED;
}
public static void main(String[] argv) {
AccessNBody obj = new AccessNBody();
final long before = System.currentTimeMillis();
obj.timeAccessNBody(200);
final long after = System.currentTimeMillis();
obj.verify();
System.out.println("benchmarks/math/AccessNBody: " + (after - before));
}
}
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