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Diffstat (limited to 'test/c/nbody.c')
| -rw-r--r-- | test/c/nbody.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/test/c/nbody.c b/test/c/nbody.c new file mode 100644 index 0000000..ff3d261 --- /dev/null +++ b/test/c/nbody.c @@ -0,0 +1,174 @@ +/* + * The Great Computer Language Shootout + * http://shootout.alioth.debian.org/ + * + * contributed by Christoph Bauer + * + */ + +#include <math.h> +#include <stdio.h> +#include <stdlib.h> + +#define pi 3.141592653589793 +#define solar_mass (4 * pi * pi) +#define days_per_year 365.24 + +struct planet { + double x, y, z; + double vx, vy, vz; + double mass; +}; + +void advance(int nbodies, struct planet * bodies, double dt) +{ + int i, j; + + for (i = 0; i < nbodies; i++) { + struct planet * b = &(bodies[i]); + for (j = i + 1; j < nbodies; j++) { + struct planet * b2 = &(bodies[j]); + double dx = b->x - b2->x; + double dy = b->y - b2->y; + double dz = b->z - b2->z; + double distance = sqrt(dx * dx + dy * dy + dz * dz); + double mag = dt / (distance * distance * distance); + b->vx -= dx * b2->mass * mag; + b->vy -= dy * b2->mass * mag; + b->vz -= dz * b2->mass * mag; + b2->vx += dx * b->mass * mag; + b2->vy += dy * b->mass * mag; + b2->vz += dz * b->mass * mag; + } + } + for (i = 0; i < nbodies; i++) { + struct planet * b = &(bodies[i]); + b->x += dt * b->vx; + b->y += dt * b->vy; + b->z += dt * b->vz; + } +} + +double energy(int nbodies, struct planet * bodies) +{ + double e; + int i, j; + + e = 0.0; + for (i = 0; i < nbodies; i++) { + struct planet * b = &(bodies[i]); + e += 0.5 * b->mass * (b->vx * b->vx + b->vy * b->vy + b->vz * b->vz); + for (j = i + 1; j < nbodies; j++) { + struct planet * b2 = &(bodies[j]); + double dx = b->x - b2->x; + double dy = b->y - b2->y; + double dz = b->z - b2->z; + double distance = sqrt(dx * dx + dy * dy + dz * dz); + e -= (b->mass * b2->mass) / distance; + } + } + return e; +} + +void offset_momentum(int nbodies, struct planet * bodies) +{ + double px = 0.0, py = 0.0, pz = 0.0; + int i; + for (i = 0; i < nbodies; i++) { + px += bodies[i].vx * bodies[i].mass; + py += bodies[i].vy * bodies[i].mass; + pz += bodies[i].vz * bodies[i].mass; + } + bodies[0].vx = - px / solar_mass; + bodies[0].vy = - py / solar_mass; + bodies[0].vz = - pz / solar_mass; +} + +#define NBODIES 5 +struct planet bodies[NBODIES] = { + { /* sun */ + 0, 0, 0, 0, 0, 0, 1.0 /*solar_mass*/ + }, + { /* jupiter */ + 4.84143144246472090e+00, + -1.16032004402742839e+00, + -1.03622044471123109e-01, + 1.66007664274403694e-03 /* * days_per_year */, + 7.69901118419740425e-03 /* * days_per_year */, + -6.90460016972063023e-05 /* * days_per_year */, + 9.54791938424326609e-04 /* * solar_mass */ + }, + { /* saturn */ + 8.34336671824457987e+00, + 4.12479856412430479e+00, + -4.03523417114321381e-01, + -2.76742510726862411e-03 /* * days_per_year */, + 4.99852801234917238e-03 /* * days_per_year */, + 2.30417297573763929e-05 /* * days_per_year */, + 2.85885980666130812e-04 /* * solar_mass */ + }, + { /* uranus */ + 1.28943695621391310e+01, + -1.51111514016986312e+01, + -2.23307578892655734e-01, + 2.96460137564761618e-03 /* * days_per_year */, + 2.37847173959480950e-03 /* * days_per_year */, + -2.96589568540237556e-05 /* * days_per_year */, + 4.36624404335156298e-05 /* * solar_mass */ + }, + { /* neptune */ + 1.53796971148509165e+01, + -2.59193146099879641e+01, + 1.79258772950371181e-01, + 2.68067772490389322e-03 /* * days_per_year */, + 1.62824170038242295e-03 /* * days_per_year */, + -9.51592254519715870e-05 /* * days_per_year */, + 5.15138902046611451e-05 /* * solar_mass */ + } +}; + +void setup_bodies(void) +{ + int i; + for (i = 0; i < NBODIES; i++) { + bodies[i].vx *= days_per_year; + bodies[i].vy *= days_per_year; + bodies[i].vz *= days_per_year; + bodies[i].mass *= solar_mass; + } +} + +int main(int argc, char ** argv) +{ + int n = argc < 2 ? 20000000 : atoi(argv[1]); + int i; + + setup_bodies(); + offset_momentum(NBODIES, bodies); + printf ("%.9f\n", energy(NBODIES, bodies)); + for (i = 1; i <= n; i++) + advance(NBODIES, bodies, 0.01); + printf ("%.9f\n", energy(NBODIES, bodies)); + return 0; +} + +/*** + build & benchmark results + +BUILD COMMANDS FOR: nbody.gcc + +Thu Jul 27 22:22:05 PDT 2006 + +/usr/bin/gcc -pipe -Wall -O3 -fomit-frame-pointer -funroll-loops -march=pentium4 -lm nbody.c -o nbody.gcc_run + +================================================================= +COMMAND LINE (%A is single numeric argument): + +nbody.gcc_run %A + +N=200000 2000000 20000000 +PROGRAM OUTPUT +============== +-0.169075164 +-0.169031665 +***/ |