marcandre	2009-10-25 05:55:40 +0900 (Sun, 25 Oct 2009)

  New Revision: 25457

  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=rev&revision=25457

  Log:
    * lib/matrix.rb (**): Optimization (up to 45% faster)

  Modified files:
    trunk/ChangeLog
    trunk/lib/matrix.rb

Index: ChangeLog
===================================================================
--- ChangeLog	(revision 25456)
+++ ChangeLog	(revision 25457)
@@ -1,3 +1,7 @@
+Sun Oct 25 05:44:34 2009  Marc-Andre Lafortune  <ruby-core@m...>
+
+	* lib/matrix.rb (**): Optimization (up to 45% faster)
+
 Sat Oct 24 14:28:40 2009  Yukihiro Matsumoto  <matz@r...>
 
 	* hash.c (rb_hash_set_default_proc): checks arity of defalt_proc
Index: lib/matrix.rb
===================================================================
--- lib/matrix.rb	(revision 25456)
+++ lib/matrix.rb	(revision 25457)
@@ -642,18 +642,12 @@
         return Matrix.identity(self.column_size) if other == 0
         other = -other
       end
-      z = x
-      n = other  - 1
-      while n != 0
-        while (div, mod = n.divmod(2)
-               mod == 0)
-          x = x * x
-          n = div
-        end
-        z *= x
-        n -= 1
+      z = nil
+      loop do
+        z = z ? z * x : x if other[0] == 1
+        return z if (other >>= 1).zero?
+        x *= x
       end
-      z
     elsif other.kind_of?(Float) || defined?(Rational) && other.kind_of?(Rational)
       Matrix.Raise ErrOperationNotDefined, "**"
     else

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