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#!/usr/bin/ruby
# The Computer Language Benchmark Shootout
# http://shootout.alioth.debian.org
#
# original code by Martin DeMello
# modified by Jabari Zakiya 3/20/05
# modified by Glenn Parker 3/28/05 (format results)
include Math
SOLAR_MASS = 4*PI*PI
DAYS_PER_YEAR = 365.24
Vector3D = Struct.new("Vector3D", :x, :y, :z)
class Vector3D
def *(val)
Vector3D.new(*self.map {|i| i * val})
end
def /(val)
Vector3D.new(*self.map {|i| i / val})
end
#in-place add with scale
# a.adds(b, s) -> a += b*s
def adds(other, scale)
self[0] += other[0]*scale; self[1] += other[1]*scale
self[2] += other[2]*scale
end
def subs(other, scale)
self[0] -= other[0]*scale; self[1] -= other[1]*scale
self[2] -= other[2]*scale
end
def magnitude
x=self[0]; y=self[1]; z=self[2]
sqrt(x*x + y*y + z*z)
end
# |self - other|
def dmag(other)
x=self[0]-other[0]; y=self[1]-other[1]; z=self[2]-other[2]
sqrt(x*x + y*y + z*z)
end
end
class Planet
attr_accessor :pos, :v, :mass
def initialize(x, y, z, vx, vy, vz, mass)
@pos = Vector3D.new(x, y, z)
@v = Vector3D.new(vx, vy, vz) * DAYS_PER_YEAR
@mass = mass * SOLAR_MASS
end
def distance(other)
self.pos.dmag(other.pos)
end
end
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)
sun = Planet.new(0, 0, 0, 0, 0, 0, 1)
class Array
def each_pair
a = []
each_index {|i|
((i+1)...length).each {|j|
yield at(i), at(j)
}
}
end
end
bodies = [sun, jupiter, saturn, uranus, neptune]
class << bodies
def advance(dt)
mag = m1 = m2 = nil
each_pair {|b1, b2|
d = b1.distance(b2)
mag = dt/(d*d*d)
m1 = b1.mass * mag
m2 = b2.mass * mag
b1.v.adds(b2.pos, m2)
b1.v.subs(b1.pos, m2)
b2.v.adds(b1.pos, m1)
b2.v.subs(b2.pos, m1)
}
each {|b| b.pos.adds(b.v, dt)}
end
def energy
e = 0
each {|b| e += 0.5 * b.mass * (b.v.magnitude ** 2) }
each_pair {|b1, b2| e -= (b1.mass * b2.mass) / b1.distance(b2) }
e
end
def offset_momentum
p = Vector3D.new(0,0,0)
sun = self[0]
each {|b| p.adds(b.v, b.mass) }
sun.v.subs(p, 1.0/sun.mass)
end
end
bodies.offset_momentum
puts "%.9f" % bodies.energy
Integer(ARGV[0]).times { bodies.advance(0.01) }
puts "%.9f" % bodies.energy
|
