akr	2013-07-08 00:21:26 +0900 (Mon, 08 Jul 2013)

  New Revision: 41826

  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=rev&revision=41826

  Log:
    * bignum.c (bary_mul_karatsuba): Unreachable code removed.  Remove
      several branches.

  Modified files:
    trunk/ChangeLog
    trunk/bignum.c
    trunk/test/-ext-/bignum/test_mul.rb

Index: ChangeLog
===================================================================
--- ChangeLog	(revision 41825)
+++ ChangeLog	(revision 41826)
@@ -1,3 +1,8 @@ https://github.com/ruby/ruby/blob/trunk/ChangeLog#L1
+Sun Jul  7 23:56:32 2013  Tanaka Akira  <akr@f...>
+
+	* bignum.c (bary_mul_karatsuba): Unreachable code removed.  Remove
+	  several branches.
+
 Sun Jul  7 22:59:06 2013  Tanaka Akira  <akr@f...>
 
 	* internal.h (rb_big_mul_normal): Declared.
Index: bignum.c
===================================================================
--- bignum.c	(revision 41825)
+++ bignum.c	(revision 41826)
@@ -1593,8 +1593,8 @@ bary_mul_karatsuba(BDIGIT *zds, size_t z https://github.com/ruby/ruby/blob/trunk/bignum.c#L1593
     size_t n;
     int sub_p, borrow, carry1, carry2, carry3;
 
-    int odd_x = 0;
     int odd_y = 0;
+    int odd_xy = 0;
 
     BDIGIT *xds0, *xds1, *yds0, *yds1, *zds0, *zds1, *zds2, *zds3;
 
@@ -1606,7 +1606,7 @@ bary_mul_karatsuba(BDIGIT *zds, size_t z https://github.com/ruby/ruby/blob/trunk/bignum.c#L1606
         odd_y = 1;
         yl--;
         if (yl < xl) {
-            odd_x = 1;
+            odd_xy = 1;
             xl--;
         }
     }
@@ -1706,15 +1706,10 @@ bary_mul_karatsuba(BDIGIT *zds, size_t z https://github.com/ruby/ruby/blob/trunk/bignum.c#L1706
     if (carry2)
         bary_add_one(zds2, zl-2*n);
 
-    if (borrow && carry1)
-        borrow = carry1 = 0;
-    if (borrow && carry3)
-        borrow = carry3 = 0;
-
-    if (borrow)
+    if (carry1 + carry3 - borrow < 0)
         bary_sub_one(zds3, zl-3*n);
-    else if (carry1 || carry3) {
-        BDIGIT c = carry1 + carry3;
+    else if (carry1 + carry3 - borrow > 0) {
+        BDIGIT c = carry1 + carry3 - borrow;
         bary_add(zds3, zl-3*n, zds3, zl-3*n, &c, 1);
     }
 
@@ -1729,13 +1724,10 @@ bary_mul_karatsuba(BDIGIT *zds, size_t z https://github.com/ruby/ruby/blob/trunk/bignum.c#L1724
     }
     */
 
-    if (odd_x && odd_y) {
+    if (odd_xy) {
         bary_muladd_1xN(zds+yl, zl-yl, yds[yl], xds, xl);
         bary_muladd_1xN(zds+xl, zl-xl, xds[xl], yds, yl+1);
     }
-    else if (odd_x) {
-        bary_muladd_1xN(zds+xl, zl-xl, xds[xl], yds, yl);
-    }
     else if (odd_y) {
         bary_muladd_1xN(zds+yl, zl-yl, yds[yl], xds, xl);
     }
Index: test/-ext-/bignum/test_mul.rb
===================================================================
--- test/-ext-/bignum/test_mul.rb	(revision 41825)
+++ test/-ext-/bignum/test_mul.rb	(revision 41826)
@@ -6,6 +6,7 @@ class TestBignum < Test::Unit::TestCase https://github.com/ruby/ruby/blob/trunk/test/-ext-/bignum/test_mul.rb#L6
 
     SIZEOF_BDIGITS = Bignum::SIZEOF_BDIGITS
     BITSPERDIG = Bignum::BITSPERDIG
+    BDIGMAX = (1 << BITSPERDIG) - 1
 
     def test_mul_normal
       x = (1 << BITSPERDIG) | 1
@@ -49,5 +50,47 @@ class TestBignum < Test::Unit::TestCase https://github.com/ruby/ruby/blob/trunk/test/-ext-/bignum/test_mul.rb#L50
       assert_equal(z, x.big_mul_karatsuba(y))
     end
 
+    def test_mul_karatsuba_odd_y
+      x = (1 << BITSPERDIG) | 1
+      y = (1 << (2*BITSPERDIG)) | 1
+      assert_equal(x.big_mul_normal(y), x.big_mul_karatsuba(y))
+    end
+
+    def test_mul_karatsuba_odd_xy
+      x = (1 << (2*BITSPERDIG)) | 1
+      y = (1 << (2*BITSPERDIG)) | 1
+      assert_equal(x.big_mul_normal(y), x.big_mul_karatsuba(y))
+    end
+
+    def test_mul_karatsuba_x1_gt_x0
+      x = (2 << BITSPERDIG) | 1
+      y = (1 << BITSPERDIG) | 2
+      assert_equal(x.big_mul_normal(y), x.big_mul_karatsuba(y))
+    end
+
+    def test_mul_karatsuba_y1_gt_y0
+      x = (1 << BITSPERDIG) | 2
+      y = (2 << BITSPERDIG) | 1
+      assert_equal(x.big_mul_normal(y), x.big_mul_karatsuba(y))
+    end
+
+    def test_mul_karatsuba_x1_gt_x0_and_y1_gt_y0
+      x = (2 << BITSPERDIG) | 1
+      y = (2 << BITSPERDIG) | 1
+      assert_equal(x.big_mul_normal(y), x.big_mul_karatsuba(y))
+    end
+
+    def test_mul_karatsuba_carry2
+      x = (1 << BITSPERDIG) | BDIGMAX
+      y = (1 << BITSPERDIG) | BDIGMAX
+      assert_equal(x.big_mul_normal(y), x.big_mul_karatsuba(y))
+    end
+
+    def test_mul_karatsuba_borrow
+      x = (BDIGMAX << BITSPERDIG) | 1
+      y = (BDIGMAX << BITSPERDIG) | 1
+      assert_equal(x.big_mul_normal(y), x.big_mul_karatsuba(y))
+    end
+
   end
 end

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