From ab359b8d8c52d007e9ee1deb8a2cf88af4bb3957 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Thu, 26 Apr 2007 08:30:10 +0000
Subject: * bignum.c (rb_big_pow): reduce multiplying for even number.

* numeric.c (int_pow): calculate power in Fixnum as possible.
  [ruby-dev:30726]


git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@12223 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 numeric.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

(limited to 'numeric.c')

diff --git a/numeric.c b/numeric.c
index 756f510ca..86728f206 100644
--- a/numeric.c
+++ b/numeric.c
@@ -2259,6 +2259,38 @@ fix_divmod(VALUE x, VALUE y)
     }
 }
 
+static VALUE
+int_pow(long x, unsigned long y)
+{
+    int neg = x < 0;
+    long z = 1;
+
+    if (neg) x = -x;
+    if (y & 1) z = x;
+    y &= ~1;
+    do {
+	while (y % 2 == 0) {
+	    long x2 = x * x;
+	    if (x2 < x || !POSFIXABLE(x2)) {
+	      bignum:
+		return rb_big_mul(rb_big_pow(rb_int2big(x), LONG2NUM(y)),
+				  rb_int2big(neg ? -z : z));
+	    }
+	    x = x2;
+	    y >>= 1;
+	}
+	{
+	    long xz = x * z;
+	    if (xz < z || xz < x || !POSFIXABLE(xz)) {
+		goto bignum;
+	    }
+	    z = xz;
+	}
+    } while (--y);
+    if (neg) z = -z;
+    return LONG2NUM(z);
+}
+
 /*
  *  call-seq:
  *    fix ** other         => Numeric
@@ -2282,7 +2314,7 @@ fix_pow(VALUE x, VALUE y)
 	if (b == 1) return x;
 	a = FIX2LONG(x);
 	if (b > 0) {
-	    return rb_big_pow(rb_int2big(a), y);
+	    return int_pow(a, b);
 	}
 	return rb_float_new(pow((double)a, (double)b));
     }
-- 
cgit