public static void main(String[] args) {
Benchmark be = new Benchmark(args);
int n = NBody.DEFAULT_ITERATIONS;
if (be.args.length > 0) {
n = Integer.parseInt(be.args[0]);
}
int size = NBody.DEFAULT_SIZE;
if (be.args.length > 1) {
size = Integer.parseInt(be.args[1]);
}
while (!be.stop()) {
SeqNBodySystem bodies = new SeqNBodySystem(NBody.generateRandomBodies(size, 1L));
if (be.verbose) System.out.printf("%.9f\n", bodies.energy());
be.start();
for (int i = 0; i < n; ++i) bodies.advance(0.01);
be.end();
if (be.verbose) System.out.printf("%.9f\n", bodies.energy());
}
}
public void advance(double dt) {
for (int i = 0; i < bodies.length; ++i) {
NBody iBody = bodies[i];
for (int j = i + 1; j < bodies.length; ++j) {
final NBody body = bodies[j];
double dx = iBody.x - body.x;
double dy = iBody.y - body.y;
double dz = iBody.z - body.z;
double dSquared = dx * dx + dy * dy + dz * dz;
double distance = Math.sqrt(dSquared);
double mag = dt / (dSquared * distance);
iBody.vx -= dx * body.mass * mag;
iBody.vy -= dy * body.mass * mag;
iBody.vz -= dz * body.mass * mag;
body.vx += dx * iBody.mass * mag;
body.vy += dy * iBody.mass * mag;
body.vz += dz * iBody.mass * mag;
}
}
for (NBody body : bodies) {
body.x += dt * body.vx;
body.y += dt * body.vy;
body.z += dt * body.vz;
}
}
