# steveklabnik/ruby forked from ruby/ruby

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 # The Computer Language Shootout # http://shootout.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 def _puts *args end 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) ] init = 200_000 # ARGV[0] n = Integer(init) 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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