* bignum.c (bigmul0): enable big_mul_toom3.

  [ruby-core:48552] [Bug #7242]

* bignum.c (bigmul1_toom3): fix incorrect calculation.
  the patch is made by Heesob Park.
  [ruby-core:48552] [Bug #7242]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37567 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 3 deletions

diff --git a/bignum.c b/bignum.c
index d2e5f944ac..97be53faf1 100644
--- a/bignum.c
+++ b/bignum.c
@@ -2501,7 +2501,7 @@ bigmul1_toom3(VALUE x, VALUE y)
     z2 = bigtrunc(bigadd(u2, u0, 0));
 
     /* z3 <- (z2 - z3) / 2 + 2 * z(inf) == (z2 - z3) / 2 + 2 * u4 */
-    z3 = bigadd(z2, z3, 0);
+    z3 = bigtrunc(bigadd(z2, z3, 0));
     bigrsh_bang(BDIGITS(z3), RBIGNUM_LEN(z3), 1);
     t = big_lshift(u4, 1); /* TODO: combining with next addition */
     z3 = bigtrunc(bigadd(z3, t, 1));
@@ -2617,8 +2617,13 @@ bigmul0(VALUE x, VALUE y)
     /* balance multiplication by slicing y when x is much smaller than y */
     if (2 * xn <= yn) return bigmul1_balance(x, y);
 
-    /* multiplication by karatsuba method */
-    return bigmul1_karatsuba(x, y);
+    if (xn < TOOM3_MUL_DIGITS) {
+	/* multiplication by karatsuba method */
+	return bigmul1_karatsuba(x, y);
+    }
+    else if (3*xn <= 2*(yn + 2))
+	return bigmul1_balance(x, y);
+    return bigmul1_toom3(x, y);
 }
 
 /*