benchmark: drop all bm_ prefix for legacy driver.rb

benchmark/*.rb is only benchmarks now. We don't need prefixes.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63928 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

benchmark/so_nbody.rb

@@ -0,0 +1,148 @@
+# 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)