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/*
* This benchmark has been ported from "The Computer Language Benchmarks Game" suite and slightly
* modified to fit the benchmarking framework.
*
* The original file is `nbody/nbody.java` from the archive available at
* http://benchmarksgame.alioth.debian.org/download/benchmarksgame-sourcecode.zip.
* See LICENSE file in the same folder (BSD 3-clause)
*
* The Computer Language Benchmarks Game
* http://benchmarksgame.alioth.debian.org/
*
* contributed by Mark C. Lewis
* modified slightly by Chad Whipkey
*
* Same program, different command-line:
* -XX:MaxMetaspaceSize=3m -XX:InitialCodeCacheSize=2048K -XX:ReservedCodeCacheSize=2048K
*/
/*
* Description: Double-precision N-body simulation.
* Main Focus: TODO
*
*/
package art_benchmarks.benchmarksgame;
// CHECKSTYLE.OFF: .*
final class NBodySystem {
private Body[] bodies;
public NBodySystem(){
bodies = new Body[]{
Body.sun(),
Body.jupiter(),
Body.saturn(),
Body.uranus(),
Body.neptune()
};
double px = 0.0;
double py = 0.0;
double pz = 0.0;
for(int i=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 void advance(double dt) {
for(int i=0; i < bodies.length; ++i) {
Body iBody = bodies[i];
for(int j=i+1; j < bodies.length; ++j) {
double dx = iBody.x - bodies[j].x;
double dy = iBody.y - bodies[j].y;
double dz = iBody.z - bodies[j].z;
double dSquared = dx * dx + dy * dy + dz * dz;
double distance = Math.sqrt(dSquared);
double mag = dt / (dSquared * distance);
iBody.vx -= dx * bodies[j].mass * mag;
iBody.vy -= dy * bodies[j].mass * mag;
iBody.vz -= dz * bodies[j].mass * mag;
bodies[j].vx += dx * iBody.mass * mag;
bodies[j].vy += dy * iBody.mass * mag;
bodies[j].vz += dz * iBody.mass * mag;
}
}
for ( Body body : bodies) {
body.x += dt * body.vx;
body.y += dt * body.vy;
body.z += dt * body.vz;
}
}
public double energy(){
double dx, dy, dz, distance;
double e = 0.0;
for (int i=0; i < bodies.length; ++i) {
Body iBody = bodies[i];
e += 0.5 * iBody.mass *
( iBody.vx * iBody.vx
+ iBody.vy * iBody.vy
+ iBody.vz * iBody.vz );
for (int j=i+1; j < bodies.length; ++j) {
Body jBody = bodies[j];
dx = iBody.x - jBody.x;
dy = iBody.y - jBody.y;
dz = iBody.z - jBody.z;
distance = Math.sqrt(dx*dx + dy*dy + dz*dz);
e -= (iBody.mass * jBody.mass) / distance;
}
}
return e;
}
}
final class Body {
static final double PI = 3.141592653589793;
static final double SOLAR_MASS = 4 * PI * PI;
static final double DAYS_PER_YEAR = 365.24;
public double x, y, z, vx, vy, vz, mass;
public Body(){}
static Body jupiter(){
Body p = new Body();
p.x = 4.84143144246472090e+00;
p.y = -1.16032004402742839e+00;
p.z = -1.03622044471123109e-01;
p.vx = 1.66007664274403694e-03 * DAYS_PER_YEAR;
p.vy = 7.69901118419740425e-03 * DAYS_PER_YEAR;
p.vz = -6.90460016972063023e-05 * DAYS_PER_YEAR;
p.mass = 9.54791938424326609e-04 * SOLAR_MASS;
return p;
}
static Body saturn(){
Body p = new Body();
p.x = 8.34336671824457987e+00;
p.y = 4.12479856412430479e+00;
p.z = -4.03523417114321381e-01;
p.vx = -2.76742510726862411e-03 * DAYS_PER_YEAR;
p.vy = 4.99852801234917238e-03 * DAYS_PER_YEAR;
p.vz = 2.30417297573763929e-05 * DAYS_PER_YEAR;
p.mass = 2.85885980666130812e-04 * SOLAR_MASS;
return p;
}
static Body uranus(){
Body p = new Body();
p.x = 1.28943695621391310e+01;
p.y = -1.51111514016986312e+01;
p.z = -2.23307578892655734e-01;
p.vx = 2.96460137564761618e-03 * DAYS_PER_YEAR;
p.vy = 2.37847173959480950e-03 * DAYS_PER_YEAR;
p.vz = -2.96589568540237556e-05 * DAYS_PER_YEAR;
p.mass = 4.36624404335156298e-05 * SOLAR_MASS;
return p;
}
static Body neptune(){
Body p = new Body();
p.x = 1.53796971148509165e+01;
p.y = -2.59193146099879641e+01;
p.z = 1.79258772950371181e-01;
p.vx = 2.68067772490389322e-03 * DAYS_PER_YEAR;
p.vy = 1.62824170038242295e-03 * DAYS_PER_YEAR;
p.vz = -9.51592254519715870e-05 * DAYS_PER_YEAR;
p.mass = 5.15138902046611451e-05 * SOLAR_MASS;
return p;
}
static Body sun(){
Body p = new Body();
p.mass = SOLAR_MASS;
return p;
}
Body offsetMomentum(double px, double py, double pz){
vx = -px / SOLAR_MASS;
vy = -py / SOLAR_MASS;
vz = -pz / SOLAR_MASS;
return this;
}
}
public final class nbody {
// CHECKSTYLE.ON: .*
private NBodySystem bodies;
public nbody() {
bodies = new NBodySystem();
}
private static final int PREDEFINED_N_STEPS = 1000;
public void solve() {
for (int i = 0; i < PREDEFINED_N_STEPS; ++i) {
bodies.advance(0.01);
}
}
public void timeNBody(int iters) {
for (int j = 0; j < iters; ++j) {
solve();
}
}
public boolean verifyNBody() {
bodies = new NBodySystem();
solve();
double expected = -0.169087605234606;
double found = bodies.energy();
if (Math.abs(expected - found) > 0.000000001) {
System.out.println("ERROR: Expected " + expected + " but found " + found);
return false;
}
return true;
}
public static void main(String[] args) {
int rc = 0;
nbody obj = new nbody();
final long before = System.currentTimeMillis();
obj.timeNBody(1000);
final long after = System.currentTimeMillis();
if (!obj.verifyNBody()) {
rc++;
}
System.out.println("art_benchmarks/benchmarksgame/nbody: " + (after - before));
System.exit(rc);
}
}
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