added fannkuch benchmark

git-svn-id: http://svn.macosforge.org/repository/ruby/MacRuby/trunk@4475 23306eb0-4c56-4727-a40e-e92c0eb68959

perf/misc/fannkuch.rb

@@ -0,0 +1,62 @@
+# From The Computer Language Benchmarks Game
+# http://shootout.alioth.debian.org/
+# Contributed by Wesley Moxam
+
+def fannkuch(n)
+  sign, maxflips, sum = 1, 0, 0
+
+  p = [nil].concat((1..n).to_a)
+  q = p.dup
+  s = p.dup
+
+  while(true)
+    # Copy and flip.
+    q1 = p[1]                # Cache 1st element.
+    if q1 != 1
+      q = p.dup
+      flips = 1
+      while(true)
+        qq = q[q1]
+        if qq == 1                # ... until 1st element is 1.
+          sum = sum + sign * flips
+          maxflips = flips if flips > maxflips # New maximum?
+          break
+        end
+        q[q1] = q1
+        if q1 >= 4
+          i, j = 2, q1 - 1
+          begin
+            q[i], q[j] = q[j], q[i]
+            i = i + 1
+            j = j - 1
+          end while i < j
+        end
+        q1 = qq
+        flips = flips + 1
+      end
+    end
+    # Permute.
+    if sign == 1
+      # Rotate 1<-2.
+      p[1], p[2] = p[2], p[1]
+      sign = -1
+    else
+      # Rotate 1<-2 and 1<-2<-3.
+      p[2], p[3] = p[3], p[2]
+      sign = 1
+      3.upto(n) do |i|
+        (s[i] =  s[i] - 1) && break unless s[i] == 1
+        return [sum, maxflips] if i == n     # Out of permutations.
+        s[i] = i
+        # Rotate 1<-...<-i+1.
+        t = p[1]
+        1.upto(i) do |j|
+          p[j] = p[j+1]
+        end
+        p[i+1] = t
+      end
+    end
+  end
+end
+
+perf_test('fannkuch') { fannkuch(9) }