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

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@25457 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 11 deletions

diff --git a/lib/matrix.rb b/lib/matrix.rb
index b577ef311..3c75751e3 100644
--- a/lib/matrix.rb
+++ b/lib/matrix.rb
@@ -642,18 +642,12 @@ class Matrix
         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