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* bignum.c (bigmul1_karatsuba): fix comment and refactoring.

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git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@20738 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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mame 2008-12-14 12:15:07 +00:00
parent bba7733b20
commit 26fc24fb0b
2 changed files with 8 additions and 4 deletions
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ChangeLog
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@ -1,3 +1,7 @@
Sun Dec 14 21:13:02 2008 Yusuke Endoh <mame@tsg.ne.jp>
* bignum.c (bigmul1_karatsuba): fix comment and refactoring.
Sun Dec 14 14:53:41 2008 Yusuke Endoh <mame@tsg.ne.jp>
* bignum.c (bigmul1_balance, bigmul1_karatsuba): remove all

8
bignum.c
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@ -1668,7 +1668,7 @@ bigmul1_karatsuba(VALUE x, VALUE y)
* where
* z2 = xh * yh
* z0 = xl * yl
* z1 = (xh + xl) * (yh + yl) - x2 - x0
* z1 = (xh + xl) * (yh + yl) - z2 - z0
*
* ref: http://en.wikipedia.org/wiki/Karatsuba_algorithm
*/
@ -1683,7 +1683,7 @@ bigmul1_karatsuba(VALUE x, VALUE y)
/* copy t1 into high bytes of the result (z2) */
MEMCPY(zds + 2 * n, BDIGITS(t1), BDIGIT, t1n);
for (i = 2 * n + t1n; i < xn + yn; i++) BDIGITS(z)[i] = 0;
for (i = 2 * n + t1n; i < xn + yn; i++) zds[i] = 0;
if (!BIGZEROP(xl) && !BIGZEROP(yl)) {
/* t2 <- xl * yl */
@ -1692,7 +1692,7 @@ bigmul1_karatsuba(VALUE x, VALUE y)
/* copy t2 into low bytes of the result (z0) */
MEMCPY(zds, BDIGITS(t2), BDIGIT, t2n);
for (i = t2n; i < 2 * n; i++) BDIGITS(z)[i] = 0;
for (i = t2n; i < 2 * n; i++) zds[i] = 0;
/* subtract t2 from middle bytes of the result (z1) */
i = xn + yn - n;
@ -1700,7 +1700,7 @@ bigmul1_karatsuba(VALUE x, VALUE y)
}
else {
/* copy 0 into low bytes of the result (z0) */
for (i = 0; i < 2 * n; i++) BDIGITS(z)[i] = 0;
for (i = 0; i < 2 * n; i++) zds[i] = 0;
}
/* subtract t1 from middle bytes of the result (z1) */