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Fix a performance bug in factor(6).

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Check if large factor is prime before applying Pollard's algorithm;
fixes "factor 2147483647111311".  Increase base if p-1 algorithm
reaches 1; fixes "factor 99999999999991".

Testcases from David A Bagley <bagleyd@tux.org>.
Fixes from Joseph Myers <jsm@NetBSD.org>.
Problem rediscovered by an attempt to factor my phone number.

A few other incidental fixes: correct a couple of factually incorrect
comments; use ident string macros; move from 4-clause to 3-clause
BSD licence (University of California copyright).

Obtained from:	NetBSD
This commit is contained in:
Tony Finch 2009-11-26 00:38:13 +00:00
parent e6af527c11
commit 38281fea3e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=199815
1 changed files with 27 additions and 21 deletions
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48
games/factor/factor.c
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@ -13,11 +13,7 @@
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
@ -35,18 +31,20 @@
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1989, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)factor.c 8.4 (Berkeley) 5/4/95";
__RCSID("$NetBSD: factor.c,v 1.13 2002/06/18 23:07:36 simonb Exp $");
#include <sys/cdefs.h>
#ifdef __COPYRIGHT
__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
The Regents of the University of California. All rights reserved.");
#endif
#ifdef __SCCSID
__SCCSID("@(#)factor.c 8.4 (Berkeley) 5/4/95");
#endif
#ifdef __RCSID
__RCSID("$NetBSD: factor.c,v 1.19 2009/08/12 05:54:31 dholland Exp $");
#endif
#ifdef __FBSDID
__FBSDID("$FreeBSD$");
#endif
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
/*
@ -63,7 +61,7 @@ static const char rcsid[] =
*
* number: factor1 factor1 factor2 factor3 factor3 factor3 ...
*
* where factor1 < factor2 < factor3 < ...
* where factor1 <= factor2 <= factor3 <= ...
*
* If no args are given, the list of numbers are read from stdin.
*/
@ -214,7 +212,9 @@ pr_fact(BIGNUM *val)
bnfact = BN_new();
BN_set_word(bnfact, *(fact - 1));
BN_sqr(bnfact, bnfact, ctx);
if (BN_cmp(bnfact, val) > 0)
if (BN_cmp(bnfact, val) > 0 ||
BN_is_prime(val, PRIME_CHECKS,
NULL, NULL, NULL) == 1)
pr_print(val);
else
pollard_pminus1(val);
@ -257,22 +257,28 @@ usage(void)
#ifdef HAVE_OPENSSL
/* pollard rho, algorithm from Jim Gillogly, May 2000 */
/* pollard p-1, algorithm from Jim Gillogly, May 2000 */
static void
pollard_pminus1(BIGNUM *val)
{
BIGNUM *base, *num, *i, *x;
BIGNUM *base, *rbase, *num, *i, *x;
base = BN_new();
rbase = BN_new();
num = BN_new();
i = BN_new();
x = BN_new();
BN_set_word(rbase, 1);
newbase:
BN_add_word(rbase, 1);
BN_set_word(i, 2);
BN_set_word(base, 2);
BN_copy(base, rbase);
for (;;) {
BN_mod_exp(base, base, i, val, ctx);
if (BN_is_one(base))
goto newbase;
BN_copy(x, base);
BN_sub_word(x, 1);