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
SOLAR_MASS = 4 * Math::PI * Math::PI
DAYS_PER_YEAR = 365.24
class Body
attr_accessor :x, :y, :z, :vx, :vy, :vz, :mass
def initialize(x, y, z, vx, vy, vz, mass)
@x = x
@y = y
@z = z
@vx = vx
@vy = vy
@vz = vz
@mass = mass
end
end
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
end
b = bodies[0]
b.vx = - px / SOLAR_MASS
b.vy = - py / SOLAR_MASS
b.vz = - pz / SOLAR_MASS
end
def energy bodies
e = 0.0
num_bodies = bodies.size
for i in 0 ... 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 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) / Math.sqrt(sq)
end
end
return e
end
def advance(bodies, dt)
num_bodies = bodies.size
for i in 0 ... num_bodies
for j in 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 * Math.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
end
end
for i in 0 ... num_bodies
bodies[i].x += bodies[i].vx * dt
bodies[i].y += bodies[i].vy * dt
bodies[i].z += bodies[i].vz * dt
end
end
def nbody n
bodies = [
# sun
Body.new(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, SOLAR_MASS),
# jupiter
Body.new(
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.new(
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.new(
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.new(
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
puts "%.9f" % (energy bodies)
n.times do
advance(bodies, 0.01)
end
puts "%.9f" % (energy bodies)
end
n = Integer(ARGV[0])
nbody n