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March 7, 2014 18:44
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ruby n-body benchmark
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# The Computer Language Benchmarks Game | |
# http://benchmarksgame.alioth.debian.org | |
# | |
# Optimized for Ruby by Jesse Millikan | |
# From version ported by Michael Neumann from the C gcc version, | |
# which was written by Christoph Bauer. | |
SOLAR_MASS = 4 * Math::PI**2 | |
DAYS_PER_YEAR = 365.24 | |
class Planet | |
attr_accessor :x, :y, :z, :vx, :vy, :vz, :mass | |
def initialize(x, y, z, vx, vy, vz, mass) | |
@x, @y, @z = x, y, z | |
@vx, @vy, @vz = vx * DAYS_PER_YEAR, vy * DAYS_PER_YEAR, vz * DAYS_PER_YEAR | |
@mass = mass * SOLAR_MASS | |
end | |
def move_from_i(bodies, nbodies, dt, i) | |
while i < nbodies | |
b2 = bodies[i] | |
dx = @x - b2.x | |
dy = @y - b2.y | |
dz = @z - b2.z | |
distance = Math.sqrt(dx * dx + dy * dy + dz * dz) | |
mag = dt / (distance * distance * distance) | |
b_mass_mag, b2_mass_mag = @mass * mag, b2.mass * mag | |
@vx -= dx * b2_mass_mag | |
@vy -= dy * b2_mass_mag | |
@vz -= dz * b2_mass_mag | |
b2.vx += dx * b_mass_mag | |
b2.vy += dy * b_mass_mag | |
b2.vz += dz * b_mass_mag | |
i += 1 | |
end | |
@x += dt * @vx | |
@y += dt * @vy | |
@z += dt * @vz | |
end | |
end | |
def energy(bodies) | |
e = 0.0 | |
nbodies = bodies.size | |
for i in 0 ... nbodies | |
b = bodies[i] | |
e += 0.5 * b.mass * (b.vx * b.vx + b.vy * b.vy + b.vz * b.vz) | |
for j in (i + 1) ... nbodies | |
b2 = bodies[j] | |
dx = b.x - b2.x | |
dy = b.y - b2.y | |
dz = b.z - b2.z | |
distance = Math.sqrt(dx * dx + dy * dy + dz * dz) | |
e -= (b.mass * b2.mass) / distance | |
end | |
end | |
e | |
end | |
def offset_momentum(bodies) | |
px, py, pz = 0.0, 0.0, 0.0 | |
for b in bodies | |
m = b.mass | |
px += b.vx * m | |
py += b.vy * m | |
pz += b.vz * m | |
end | |
b = bodies[0] | |
b.vx = - px / SOLAR_MASS | |
b.vy = - py / SOLAR_MASS | |
b.vz = - pz / SOLAR_MASS | |
end | |
BODIES = [ | |
# sun | |
Planet.new(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0), | |
# jupiter | |
Planet.new( | |
4.84143144246472090e+00, | |
-1.16032004402742839e+00, | |
-1.03622044471123109e-01, | |
1.66007664274403694e-03, | |
7.69901118419740425e-03, | |
-6.90460016972063023e-05, | |
9.54791938424326609e-04), | |
# saturn | |
Planet.new( | |
8.34336671824457987e+00, | |
4.12479856412430479e+00, | |
-4.03523417114321381e-01, | |
-2.76742510726862411e-03, | |
4.99852801234917238e-03, | |
2.30417297573763929e-05, | |
2.85885980666130812e-04), | |
# uranus | |
Planet.new( | |
1.28943695621391310e+01, | |
-1.51111514016986312e+01, | |
-2.23307578892655734e-01, | |
2.96460137564761618e-03, | |
2.37847173959480950e-03, | |
-2.96589568540237556e-05, | |
4.36624404335156298e-05), | |
# neptune | |
Planet.new( | |
1.53796971148509165e+01, | |
-2.59193146099879641e+01, | |
1.79258772950371181e-01, | |
2.68067772490389322e-03, | |
1.62824170038242295e-03, | |
-9.51592254519715870e-05, | |
5.15138902046611451e-05) | |
] | |
n = Integer(ARGV[0]) | |
offset_momentum(BODIES) | |
puts "%.9f" % energy(BODIES) | |
nbodies = BODIES.size | |
dt = 0.01 | |
n.times do | |
i = 0 | |
while i < nbodies | |
b = BODIES[i] | |
b.move_from_i(BODIES, nbodies, dt, i + 1) | |
i += 1 | |
end | |
end | |
puts "%.9f" % energy(BODIES) |
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