# The Computer Language Benchmarks Game # http://shootout.alioth.debian.org/ # # originally by Kevin Carson # modified by Tupteq, Fredrik Johansson, and Daniel Nanz # modified by Maciej Fijalkowski # 2to3 import sys def combinations(l): result = [] for x in range(len(l) - 1): ls = l[x+1:] for y in ls: result.append((l[x],y)) return result PI = 3.14159265358979323 SOLAR_MASS = 4 * PI * PI DAYS_PER_YEAR = 365.24 BODIES = { 'sun': ([0.0, 0.0, 0.0], [0.0, 0.0, 0.0], 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) } SYSTEM = list(BODIES.values()) PAIRS = combinations(SYSTEM) def advance(dt, n, bodies=SYSTEM, pairs=PAIRS): print(len(pairs)) for i in range(n): for (([x1, y1, z1], v1, m1), ([x2, y2, z2], v2, m2)) in pairs: dx = x1 - x2 dy = y1 - y2 dz = z1 - z2 mag = dt * ((dx * dx + dy * dy + dz * dz) ** (-1.5)) b1m = m1 * mag b2m = m2 * mag v1[0] -= dx * b2m v1[1] -= dy * b2m v1[2] -= dz * b2m v2[0] += dx * b1m v2[1] += dy * b1m v2[2] += dz * b1m for (r, [vx, vy, vz], m) in bodies: r[0] += dt * vx r[1] += dt * vy r[2] += dt * vz def report_energy(bodies=SYSTEM, pairs=PAIRS, e=0.0): for (((x1, y1, z1), v1, m1), ((x2, y2, z2), v2, m2)) in pairs: dx = x1 - x2 dy = y1 - y2 dz = z1 - z2 e -= (m1 * m2) / ((dx * dx + dy * dy + dz * dz) ** 0.5) for (r, [vx, vy, vz], m) in bodies: e += m * (vx * vx + vy * vy + vz * vz) / 2. print("%.9f" % e) def offset_momentum(ref, bodies=SYSTEM, px=0.0, py=0.0, pz=0.0): for (r, [vx, vy, vz], m) in bodies: px -= vx * m py -= vy * m pz -= vz * m (r, v, m) = ref v[0] = px / m v[1] = py / m v[2] = pz / m def main(n, ref='sun'): offset_momentum(BODIES[ref]) report_energy() advance(0.01, n) report_energy() if __name__ == '__main__': main(int(sys.argv[1]))