source code
/* The Computer Language Benchmarks Game
http://benchmarksgame.alioth.debian.org/
Contributed by Robert F. Tobler
Modified to use SIMD vectors by Anthony Lloyd and Paul Westcott
*/
using System;
using System.Numerics;
using System.Runtime.CompilerServices;
public static class NBody
{
const double dt = 0.01;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static double[] createBodies()
{
const double Pi = 3.141592653589793;
const double Solarmass = 4 * Pi * Pi;
const double DaysPeryear = 365.24;
const double jmass = 9.54791938424326609e-04 * Solarmass;
const double jvx = 1.66007664274403694e-03 * DaysPeryear;
const double jvy = 7.69901118419740425e-03 * DaysPeryear;
const double jvz = -6.90460016972063023e-05 * DaysPeryear;
const double smass = 2.85885980666130812e-04 * Solarmass;
const double svx = -2.76742510726862411e-03 * DaysPeryear;
const double svy = 4.99852801234917238e-03 * DaysPeryear;
const double svz = 2.30417297573763929e-05 * DaysPeryear;
const double umass = 4.36624404335156298e-05 * Solarmass;
const double uvx = 2.96460137564761618e-03 * DaysPeryear;
const double uvy = 2.37847173959480950e-03 * DaysPeryear;
const double uvz = -2.96589568540237556e-05 * DaysPeryear;
const double nmass = 5.15138902046611451e-05 * Solarmass;
const double nvx = 2.68067772490389322e-03 * DaysPeryear;
const double nvy = 1.62824170038242295e-03 * DaysPeryear;
const double nvz = -9.51592254519715870e-05 * DaysPeryear;
return new double[] {
// sun
(jvx * jmass + svx * smass + uvx * umass + nvx * nmass)/-Solarmass,
(jvy * jmass + svy * smass + uvy * umass + nvy * nmass)/-Solarmass,
(jvz * jmass + svz * smass + uvz * umass + nvz * nmass)/-Solarmass,
0.0,
0.0, 0.0, 0.0, 0.0,
Solarmass,
// jupiter
jvx, jvy, jvz, 0.0,
4.84143144246472090e+00, -1.16032004402742839e+00, -1.03622044471123109e-01, 0.0,
jmass,
// saturn
svx, svy, svz, 0.0,
8.34336671824457987e+00, 4.12479856412430479e+00, -4.03523417114321381e-01, 0.0,
smass,
// uranus
uvx, uvy, uvz, 0.0,
1.28943695621391310e+01, -1.51111514016986312e+01, -2.23307578892655734e-01, 0.0,
umass,
// neptune
nvx, nvy, nvz, 0.0,
1.53796971148509165e+01, -2.59193146099879641e+01, 1.79258772950371181e-01, 0.0,
nmass,
};
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static double energy(double[] bodies)
{
double e = 0.0;
for(int i=0; i<bodies.Length; i+=9)
{
var Vi = new Vector<double>(bodies,i);
var Xi = new Vector<double>(bodies,i+4);
var imass = bodies[i+8];
e += 0.5 * imass * Vector.Dot(Vi,Vi);
for(int j=i+9; j<bodies.Length; j+=9)
{
var DX = Xi - new Vector<double>(bodies,j+4);
e -= imass * bodies[j+8] / Math.Sqrt(Vector.Dot(DX,DX));
}
}
return e;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static void advance(double[] bodies)
{
for(int i=0; i<bodies.Length; i+=9)
{
var Vi = new Vector<double>(bodies,i);
var Xi = new Vector<double>(bodies,i+4);
var MASSi = new Vector<double>(bodies[i+8]);
for(int j=i+9; j<bodies.Length; j+=9)
{
var DX = new Vector<double>(bodies,j+4) - Xi;
var d2 = Vector.Dot(DX, DX);
var MAG = new Vector<double>(dt / (d2 * Math.Sqrt(d2)));
var MASSj = new Vector<double>(bodies[j+8]);
Vi += DX * MASSj * MAG;
(new Vector<double>(bodies,j) - DX * MASSi * MAG).CopyTo(bodies,j);
}
(Vi * dt + Xi).CopyTo(bodies,i+4);
Vi.CopyTo(bodies,i);
}
}
public static void Main(String[] args)
{
var bodies = createBodies();
Console.Out.WriteLineAsync(energy(bodies).ToString("F9"));
int n = args.Length > 0 ? Int32.Parse(args[0]) : 10000;
while(n-->0) advance(bodies);
Console.Out.WriteLineAsync(energy(bodies).ToString("F9"));
}
}