The Computer Language
Benchmarks Game

n-body C# .NET Core #4 program

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"));
    }
}
    

notes, command-line, and program output

NOTES:
64-bit Ubuntu quad core
2.0.0-preview2-006497
"System.GC.Server": true


Thu, 06 Jul 2017 17:54:37 GMT

MAKE:
cp nbody.csharpcore-4.csharpcore Program.cs
cp Include/csharpcore/tmp.csproj .
cp Include/csharpcore/runtimeconfig.template.json .
mkdir obj
cp Include/csharpcore/tmp.csproj.nuget.g.props ./obj
cp Include/csharpcore/tmp.csproj.nuget.g.targets ./obj
/usr/bin/dotnet build -c Release
Microsoft (R) Build Engine version 15.3.388.41745 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  tmp -> /home/dunham/benchmarksgame_quadcore/nbody/tmp/bin/Release/netcoreapp2.0/tmp.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:05.70

13.51s to complete and log all make actions

COMMAND LINE:
/usr/bin/dotnet ./bin/Release/netcoreapp2.0/tmp.dll 50000000

PROGRAM OUTPUT:
-0.169075164
-0.169059907