source code
/* The Computer Language Benchmarks game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
Naive transliteration from Michael Ferguson's Chapel program
contributed by Isaac Gouy
*/
// mtime side-effect
import java.io.FileOutputStream;
import java.io.FileNotFoundException;
final class Body {
public double x, y, z, vx, vy, vz, 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;
}
}
public final class startup {
static double PI = 3.141592653589793;
static double SOLAR_MASS = 4 * PI * PI;
static double DAYS_PER_YEAR = 365.24;
static void offsetMomentum(Body[] bodies) {
double px = 0.0;
double py = 0.0;
double pz = 0.0;
Body b;
for(int i=0; i < bodies.length; ++i) {
b = bodies[i];
px += b.vx * b.mass;
py += b.vy * b.mass;
pz += b.vz * b.mass;
}
b = bodies[0];
b.vx = -px / SOLAR_MASS;
b.vy = -py / SOLAR_MASS;
b.vz = -pz / SOLAR_MASS;
}
static double energy(Body[] bodies){
double e = 0.0;
for (int i=0; i < bodies.length; ++i) {
Body b = bodies[i];
double sq = b.vx * b.vx + b.vy * b.vy + b.vz * b.vz;
e += 0.5 * bodies[i].mass * sq;
for (int j=i+1; j < bodies.length; ++j) {
double dx = b.x - bodies[j].x;
double dy = b.y - bodies[j].y;
double dz = b.z - bodies[j].z;
sq = dx * dx + dy * dy + dz * dz;
e -= (b.mass * bodies[j].mass) / Math.sqrt(sq);
}
}
return e;
}
static void advance(Body[] bodies, double dt) {
double dx, dy, dz, dposNormSq, mag, mj, mi;
for(int i=0; i < bodies.length; ++i) {
for(int j=i+1; j < bodies.length; ++j) {
dx = bodies[i].x - bodies[j].x;
dy = bodies[i].y - bodies[j].y;
dz = bodies[i].z - bodies[j].z;
dposNormSq = dx*dx + dy*dy + dz*dz;
mag = dt / (dposNormSq * Math.sqrt(dposNormSq));
mj = bodies[j].mass * mag;
bodies[i].vx -= dx * mj;
bodies[i].vy -= dy * mj;
bodies[i].vz -= dz * mj;
mi = bodies[i].mass * mag;
bodies[j].vx += dx * mi;
bodies[j].vy += dy * mi;
bodies[j].vz += dz * mi;
}
}
for(int i=0; i < bodies.length; ++i) {
bodies[i].x += bodies[i].vx * dt;
bodies[i].y += bodies[i].vy * dt;
bodies[i].z += bodies[i].vz * dt;
}
}
static void nbody(int n) {
var bodies = new Body[]{
// sun
new Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS),
// jupiter
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
),
new Body(
// saturn
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
),
new Body(
// uranus
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
),
new Body(
// neptune
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
)
};
offsetMomentum(bodies);
System.out.printf("%.9f\n", energy(bodies));
for (int i=0; i<n; ++i) {
advance(bodies, 0.01);
}
System.out.printf("%.9f\n", energy(bodies));
}
public static void main(String[] args) {
int n = Integer.parseInt(args[0]);
// in-process warmup
for (int i=0; i<3000; ++i) {
System.out.println("-0.169075164");
System.out.println("-0.169083713");
}
// mtime side-effect
try { FileOutputStream o = new FileOutputStream("./one");
} catch (FileNotFoundException e) { }
nbody(n);
// mtime side-effect
try { FileOutputStream o = new FileOutputStream("./two");
} catch (FileNotFoundException e) { }
}
}
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
java 23 2024-09-17
Java HotSpot(TM) 64-Bit Server VM
(build 23+37-2369,
mixed mode, sharing)
Fri, 20 Sep 2024 17:52:16 GMT
MAKE:
mv startup.java-0.java startup.java
/opt/src/jdk-23/bin/javac -d . -cp . startup.java
1.72s to complete and log all make actions
COMMAND LINE:
/opt/src/jdk-23/bin/java -cp . startup 200000
(TRUNCATED) PROGRAM OUTPUT:
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