2 * The Great Computer Language Shootout
3 * http://shootout.alioth.debian.org/
5 * contributed by Christoph Bauer
13 #define pi 3.141592653589793
14 #define solar_mass (4 * pi * pi)
15 #define days_per_year 365.24
23 void advance(int nbodies, struct planet * bodies, double dt)
27 for (i = 0; i < nbodies; i++) {
28 struct planet * b = &(bodies[i]);
29 for (j = i + 1; j < nbodies; j++) {
30 struct planet * b2 = &(bodies[j]);
31 double dx = b->x - b2->x;
32 double dy = b->y - b2->y;
33 double dz = b->z - b2->z;
34 double distance = sqrt(dx * dx + dy * dy + dz * dz);
35 double mag = dt / (distance * distance * distance);
36 b->vx -= dx * b2->mass * mag;
37 b->vy -= dy * b2->mass * mag;
38 b->vz -= dz * b2->mass * mag;
39 b2->vx += dx * b->mass * mag;
40 b2->vy += dy * b->mass * mag;
41 b2->vz += dz * b->mass * mag;
44 for (i = 0; i < nbodies; i++) {
45 struct planet * b = &(bodies[i]);
52 double energy(int nbodies, struct planet * bodies)
58 for (i = 0; i < nbodies; i++) {
59 struct planet * b = &(bodies[i]);
60 e += 0.5 * b->mass * (b->vx * b->vx + b->vy * b->vy + b->vz * b->vz);
61 for (j = i + 1; j < nbodies; j++) {
62 struct planet * b2 = &(bodies[j]);
63 double dx = b->x - b2->x;
64 double dy = b->y - b2->y;
65 double dz = b->z - b2->z;
66 double distance = sqrt(dx * dx + dy * dy + dz * dz);
67 e -= (b->mass * b2->mass) / distance;
73 void offset_momentum(int nbodies, struct planet * bodies)
75 double px = 0.0, py = 0.0, pz = 0.0;
77 for (i = 0; i < nbodies; i++) {
78 px += bodies[i].vx * bodies[i].mass;
79 py += bodies[i].vy * bodies[i].mass;
80 pz += bodies[i].vz * bodies[i].mass;
82 bodies[0].vx = - px / solar_mass;
83 bodies[0].vy = - py / solar_mass;
84 bodies[0].vz = - pz / solar_mass;
88 struct planet bodies[NBODIES] = {
90 0, 0, 0, 0, 0, 0, solar_mass
93 4.84143144246472090e+00,
94 -1.16032004402742839e+00,
95 -1.03622044471123109e-01,
96 1.66007664274403694e-03 * days_per_year,
97 7.69901118419740425e-03 * days_per_year,
98 -6.90460016972063023e-05 * days_per_year,
99 9.54791938424326609e-04 * solar_mass
102 8.34336671824457987e+00,
103 4.12479856412430479e+00,
104 -4.03523417114321381e-01,
105 -2.76742510726862411e-03 * days_per_year,
106 4.99852801234917238e-03 * days_per_year,
107 2.30417297573763929e-05 * days_per_year,
108 2.85885980666130812e-04 * solar_mass
111 1.28943695621391310e+01,
112 -1.51111514016986312e+01,
113 -2.23307578892655734e-01,
114 2.96460137564761618e-03 * days_per_year,
115 2.37847173959480950e-03 * days_per_year,
116 -2.96589568540237556e-05 * days_per_year,
117 4.36624404335156298e-05 * solar_mass
120 1.53796971148509165e+01,
121 -2.59193146099879641e+01,
122 1.79258772950371181e-01,
123 2.68067772490389322e-03 * days_per_year,
124 1.62824170038242295e-03 * days_per_year,
125 -9.51592254519715870e-05 * days_per_year,
126 5.15138902046611451e-05 * solar_mass
130 int main(int argc, char ** argv)
132 int n = atoi(argv[1]);
135 offset_momentum(NBODIES, bodies);
136 printf ("%.9f\n", energy(NBODIES, bodies));
137 for (i = 1; i <= n; i++)
138 advance(NBODIES, bodies, 0.01);
139 printf ("%.9f\n", energy(NBODIES, bodies));