source code
# The Computer Language Benchmarks Game
# https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
#
# Naive transliteration from Michael Ferguson's Chapel program
# contributed by Isaac Gouy
from math import sqrt
import sys
PI = 3.14159265358979323
SOLAR_MASS = 4 * PI * PI
DAYS_PER_YEAR = 365.24
class Body:
def __init__(self, x, y, z, vx, vy, vz, mass):
self.x = x
self.y = y
self.z = z
self.vx = vx
self.vy = vy
self.vz = vz
self.mass = mass
def offset_momentum(bodies):
px, py, pz = 0.0, 0.0, 0.0
for b in bodies:
px += b.vx * b.mass
py += b.vy * b.mass
pz += b.vz * b.mass
b = bodies[0]
b.vx = - px / SOLAR_MASS
b.vy = - py / SOLAR_MASS
b.vz = - pz / SOLAR_MASS
def energy(bodies):
e = 0.0
num_bodies = len(bodies)
for i in range(num_bodies):
b = bodies[i]
sq = b.vx * b.vx + b.vy * b.vy + b.vz * b.vz
e += 0.5 * bodies[i].mass * sq
for j in range(i+1, num_bodies):
dx = b.x - bodies[j].x
dy = b.y - bodies[j].y
dz = b.z - bodies[j].z
sq = dx * dx + dy * dy + dz * dz
e -= (b.mass * bodies[j].mass) / sqrt(sq)
return e
def advance(bodies, dt):
num_bodies = len(bodies)
for i in range(num_bodies):
for j in range(i+1, num_bodies):
dx = bodies[i].x - bodies[j].x
dy = bodies[i].y - bodies[j].y
dz = bodies[i].z - bodies[j].z
dpos_norm_sq = dx**2 + dy**2 + dz**2
mag = dt / (dpos_norm_sq * sqrt(dpos_norm_sq))
mj = bodies[j].mass * mag
bodies[i].vx -= dx * mj
bodies[i].vy -= dy * mj
bodies[i].vz -= dz * mj
mi = bodies[i].mass * mag
bodies[j].vx += dx * mi
bodies[j].vy += dy * mi
bodies[j].vz += dz * mi
for i in range(num_bodies):
bodies[i].x += bodies[i].vx * dt
bodies[i].y += bodies[i].vy * dt
bodies[i].z += bodies[i].vz * dt
def nbody(n):
bodies = [
# sun
Body(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS),
# jupiter
Body(
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
Body(
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
Body(
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
Body(
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
)
]
offset_momentum(bodies)
print("%.9f" % energy(bodies))
for i in range(n):
advance(bodies, 0.01)
print("%.9f" % energy(bodies))
def main(n):
nbody(n)
if __name__ == '__main__':
main(int(sys.argv[1]))
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
Python 3.13.0
Sat, 12 Oct 2024 04:28:59 GMT
MAKE:
mv nbody.python3-8.python3 nbody.py
pyright .
0 errors, 0 warnings, 0 informations
4.89s to complete and log all make actions
COMMAND LINE:
/opt/src/Python-3.13.0/bin/python3 -OO nbody.py 50000000
PROGRAM OUTPUT:
-0.169075164
-0.169059907