source code
/* The Computer Language Benchmarks Game
http://benchmarksgame.alioth.debian.org/
contributed by Isaac Gouy, optimization and use of more C# idioms by Robert F. Tobler
small optimizations by Anthony Lloyd
*/
using System;
using System.Runtime.CompilerServices;
class Body { public double vx, vy, vz, x, y, z, mass; }
public static class NBody
{
const double Pi = 3.141592653589793;
const double Solarmass = 4 * Pi * Pi;
const double DaysPeryear = 365.24;
const double dt = 0.01;
const int LENGTH = 5;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static Body[] createBodies()
{
var jupiter = new Body {
x = 4.84143144246472090e+00,
y = -1.16032004402742839e+00,
z = -1.03622044471123109e-01,
vx = 1.66007664274403694e-03 * DaysPeryear,
vy = 7.69901118419740425e-03 * DaysPeryear,
vz = -6.90460016972063023e-05 * DaysPeryear,
mass = 9.54791938424326609e-04 * Solarmass,
};
var saturn = new Body {
x = 8.34336671824457987e+00,
y = 4.12479856412430479e+00,
z = -4.03523417114321381e-01,
vx = -2.76742510726862411e-03 * DaysPeryear,
vy = 4.99852801234917238e-03 * DaysPeryear,
vz = 2.30417297573763929e-05 * DaysPeryear,
mass = 2.85885980666130812e-04 * Solarmass,
};
var uranus = new Body {
x = 1.28943695621391310e+01,
y = -1.51111514016986312e+01,
z = -2.23307578892655734e-01,
vx = 2.96460137564761618e-03 * DaysPeryear,
vy = 2.37847173959480950e-03 * DaysPeryear,
vz = -2.96589568540237556e-05 * DaysPeryear,
mass = 4.36624404335156298e-05 * Solarmass,
};
var neptune = new Body {
x = 1.53796971148509165e+01,
y = -2.59193146099879641e+01,
z = 1.79258772950371181e-01,
vx = 2.68067772490389322e-03 * DaysPeryear,
vy = 1.62824170038242295e-03 * DaysPeryear,
vz = -9.51592254519715870e-05 * DaysPeryear,
mass = 5.15138902046611451e-05 * Solarmass,
};
var sun = new Body {
mass = Solarmass,
vx = (jupiter.vx * jupiter.mass + saturn.vx * saturn.mass
+uranus.vx * uranus.mass + neptune.vx * neptune.mass)/-Solarmass,
vy = (jupiter.vy * jupiter.mass + saturn.vy * saturn.mass
+uranus.vy * uranus.mass + neptune.vy * neptune.mass)/-Solarmass,
vz = (jupiter.vz * jupiter.mass + saturn.vz * saturn.mass
+uranus.vz * uranus.mass + neptune.vz * neptune.mass)/-Solarmass,
};
return new Body[LENGTH] {sun, jupiter, saturn, uranus, neptune};
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static double energy(Body[] bodies)
{
double e = 0.0;
for(int i=0; i<LENGTH; ++i)
{
var bi = bodies[i];
double ix = bi.x, iy = bi.y, iz = bi.z, imass = bi.mass;
e += 0.5 * imass * (bi.vx*bi.vx + bi.vy*bi.vy + bi.vz*bi.vz);
for(int j=i+1; j<LENGTH; ++j)
{
var bj = bodies[j];
double dx = ix - bj.x, dy = iy - bj.y, dz = iz - bj.z;
e -= imass * bj.mass / Math.Sqrt(dx * dx + dy * dy + dz * dz);
}
}
return e;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static void advance(Body[] bodies)
{
for(int i=0; i<LENGTH; ++i)
{
var bi = bodies[i];
double ix = bi.x, iy = bi.y, iz = bi.z;
double ivx = bi.vx, ivy = bi.vy, ivz = bi.vz, imass = bi.mass;
for(int j=i+1; j<LENGTH; ++j)
{
var bj = bodies[j];
double dx = bj.x - ix, dy = bj.y - iy, dz = bj.z - iz;
double d2 = dx * dx + dy * dy + dz * dz;
double mag = dt / (d2 * Math.Sqrt(d2));
ivx += bj.mass * dx * mag; bj.vx -= imass * dx * mag;
ivy += bj.mass * dy * mag; bj.vy -= imass * dy * mag;
ivz += bj.mass * dz * mag; bj.vz -= imass * dz * mag;
}
if(i!=LENGTH-1) { bi.vx = ivx; bi.vy = ivy; bi.vz = ivz; }
bi.x = ix + ivx * dt; bi.y = iy + ivy * dt; bi.z = iz + ivz * dt;
}
}
public static void Main(String[] args)
{
var bodies = createBodies();
Console.Out.WriteLineAsync(energy(bodies).ToString("F9"));
for(int i=args.Length>0 ? int.Parse(args[0]) : 10000; i>0; --i)
advance(bodies);
Console.Out.WriteLineAsync(energy(bodies).ToString("F9"));
}
}