The Computer Language
22.05 Benchmarks Game

n-body C++ g++ #3 program

source code

/* The Computer Language Benchmarks Game
   https://salsa.debian.org/benchmarksgame-team/benchmarksgame/

   contributed by Mark C. Lewis
*/

#include <cmath>
#include <cstdio>
#include <cstdlib>

class Body {
    public:
        constexpr static const double PI = 3.141592653589793;    
        constexpr static const double SOLAR_MASS = 4 * PI * PI;
        constexpr static const double DAYS_PER_YEAR = 365.24;

        double x, y, z, vx, vy, vz, mass;
    
        Body():x(0.0),y(0.0),z(0.0),vx(0.0),vy(0.0),vz(0.0),mass(0.0){}    
    
        static Body planetJupiter(){
           Body p;
           p.x = 4.84143144246472090e+00;
           p.y = -1.16032004402742839e+00;
           p.z = -1.03622044471123109e-01;
           p.vx = 1.66007664274403694e-03 * DAYS_PER_YEAR;
           p.vy = 7.69901118419740425e-03 * DAYS_PER_YEAR;
           p.vz = -6.90460016972063023e-05 * DAYS_PER_YEAR;
           p.mass = 9.54791938424326609e-04 * SOLAR_MASS;                     
           return p;
        }    
    
        static Body planetSaturn(){
           Body p;
           p.x = 8.34336671824457987e+00;
           p.y = 4.12479856412430479e+00;
           p.z = -4.03523417114321381e-01;
           p.vx = -2.76742510726862411e-03 * DAYS_PER_YEAR;
           p.vy = 4.99852801234917238e-03 * DAYS_PER_YEAR;
           p.vz = 2.30417297573763929e-05 * DAYS_PER_YEAR;
           p.mass = 2.85885980666130812e-04 * SOLAR_MASS;                     
           return p;
        }    
    
        static Body planetUranus(){
           Body p;
           p.x = 1.28943695621391310e+01;
           p.y = -1.51111514016986312e+01;
           p.z = -2.23307578892655734e-01;
           p.vx = 2.96460137564761618e-03 * DAYS_PER_YEAR;
           p.vy = 2.37847173959480950e-03 * DAYS_PER_YEAR;
           p.vz = -2.96589568540237556e-05 * DAYS_PER_YEAR;
           p.mass = 4.36624404335156298e-05 * SOLAR_MASS;                         
           return p;
        }        

        static Body planetNeptune(){
           Body p;
           p.x = 1.53796971148509165e+01;
           p.y = -2.59193146099879641e+01;
           p.z = 1.79258772950371181e-01;
           p.vx = 2.68067772490389322e-03 * DAYS_PER_YEAR;
           p.vy = 1.62824170038242295e-03 * DAYS_PER_YEAR;
           p.vz = -9.51592254519715870e-05 * DAYS_PER_YEAR;
           p.mass = 5.15138902046611451e-05 * SOLAR_MASS;                     
           return p;
        }
    
        static Body centralBody(){
           Body p;
           p.mass = SOLAR_MASS;                     
           return p;
        }            
        
        void momentum(double px, double py, double pz){
           vx = -px / SOLAR_MASS;
           vy = -py / SOLAR_MASS;
           vz = -pz / SOLAR_MASS;           
        }                                     
};

class NBodySystem {        
    private:
        int numBodies;
        Body bodies[5];
                 
    public:
        NBodySystem():numBodies(5) {            
            bodies[0] = Body::centralBody();
            bodies[1] = Body::planetJupiter();
            bodies[2] = Body::planetSaturn();
            bodies[3] = Body::planetUranus();
            bodies[4] = Body::planetNeptune();    
            
            double px = 0.0;
            double py = 0.0;    
            double pz = 0.0;                    
            for(int i=0; i < numBodies; ++i) {                                                    
                px += bodies[i].vx * bodies[i].mass;
                py += bodies[i].vy * bodies[i].mass;        
                pz += bodies[i].vz * bodies[i].mass;                       
            }        
            bodies[0].momentum(px,py,pz);
        }
    
    
        double energy(){        
            double dx, dy, dz, distance;    
            double e = 0.0;           
        
            for (int i=0; i < numBodies; ++i) {
                e += 0.5 * bodies[i].mass * 
                   ( bodies[i].vx * bodies[i].vx 
                   + bodies[i].vy * bodies[i].vy 
                   + bodies[i].vz * bodies[i].vz );
               
                for (int j=i+1; j < numBodies; ++j) {
                    dx = bodies[i].x - bodies[j].x;
                    dy = bodies[i].y - bodies[j].y;
                    dz = bodies[i].z - bodies[j].z;
                
                    distance = std::sqrt(dx*dx + dy*dy + dz*dz);
                    e -= (bodies[i].mass * bodies[j].mass) / distance;
                }
            }
            return e;
        }           
           
        void advance(double dt) {
           double dx, dy, dz, distance, mag;    
    
            for(int i=0; i < numBodies; ++i) {
                for(int j=i+1; j < numBodies; ++j) {
            
                    dx = bodies[i].x - bodies[j].x;
                    dy = bodies[i].y - bodies[j].y;
                    dz = bodies[i].z - bodies[j].z;
                
                    distance = std::sqrt(dx*dx + dy*dy + dz*dz);
                    mag = dt / (distance * distance * distance);
                
                    bodies[i].vx -= dx * bodies[j].mass * mag;
                    bodies[i].vy -= dy * bodies[j].mass * mag;
                    bodies[i].vz -= dz * bodies[j].mass * mag;
                
                    bodies[j].vx += dx * bodies[i].mass * mag;
                    bodies[j].vy += dy * bodies[i].mass * mag;
                    bodies[j].vz += dz * bodies[i].mass * mag;
                }
            }
        
            for(int i=0; i < numBodies; ++i) {
                bodies[i].x += dt * bodies[i].vx;
                bodies[i].y += dt * bodies[i].vy;
                bodies[i].z += dt * bodies[i].vz;
            }
        }                                                                                                                            
};


int main(int argc,char **argv) {
   int n = std::atoi(argv[1]);
   
    NBodySystem solarSystem;
    
    std::printf("%.9f\n", solarSystem.energy() );
    for (int i=0; i<n; ++i) {
       solarSystem.advance(0.01);
    }
    std::printf("%.9f\n", solarSystem.energy() );

    return 0;
}
    

notes, command-line, and program output

NOTES:
64-bit Ubuntu quad core
11.2.0-19ubuntu1


Mon, 02 May 2022 20:40:46 GMT

MAKE:
/usr/bin/g++ -c -pipe -O3 -fomit-frame-pointer -march=ivybridge   nbody.gpp-3.c++ -o nbody.gpp-3.c++.o &&  \
        /usr/bin/g++ nbody.gpp-3.c++.o -o nbody.gpp-3.gpp_run  
rm nbody.gpp-3.c++

2.58s to complete and log all make actions

COMMAND LINE:
./nbody.gpp-3.gpp_run 50000000

PROGRAM OUTPUT:
-0.169075164
-0.169059907