summaryrefslogtreecommitdiff
path: root/jni/ruby/benchmark/bm_so_nbody.rb
blob: d6c5bb9e61f12a0148f1f69d51a6eb4437bd7825 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
# 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)