* 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: svn+ssh://ci.ruby-lang.org/ruby/trunk@12223 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 45 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index 556419bf54..9520add6e7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Thu Apr 26 17:31:00 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* bignum.c (rb_big_pow): reduce multiplying for even number.
+
+	* numeric.c (int_pow): calculate power in Fixnum as possible.
+	  [ruby-dev:30726]
+
 Thu Apr 26 17:18:51 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* parse.y: fixes for ripper.
diff --git a/bignum.c b/bignum.c
index aec25c13d9..ba107e9edc 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1552,22 +1552,20 @@ rb_big_pow(VALUE x, VALUE y)
       case T_FIXNUM:
 	yy = FIX2LONG(y);
 	if (yy > 0) {
-	    VALUE z = x;
+	    VALUE z = (yy & 1) ? x : 0;
 
 	    if (RBIGNUM(x)->len * SIZEOF_BDIGITS * yy > 1024*1024) {
 		rb_warn("in a**b, b may be too big");
 		d = (double)yy;
 		break;
 	    }
-	    for (;;) {
-		yy -= 1;
-		if (yy == 0) break;
-		while (yy % 2 == 0) {
+	    while (yy &= ~1) {
+		do {
 		    yy /= 2;
 		    x = rb_big_mul0(x, x);
 		    if (!BDIGITS(x)[RBIGNUM(x)->len-1]) RBIGNUM(x)->len--;
-		}
-		z = rb_big_mul0(z, x);
+		} while (yy % 2 == 0);
+		z = z ? rb_big_mul0(z, x) : x;
 		if (!BDIGITS(z)[RBIGNUM(z)->len-1]) RBIGNUM(z)->len--;
 	    }
 	    return bignorm(z);
diff --git a/numeric.c b/numeric.c
index 756f510ca5..86728f2063 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));
     }