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Original patch from: perfpow.c.diff
-= BEGIN original header =-
Copyright 1998, 1999, 2000, 2001, 2005, 2008 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library. If not, see http://www.gnu.org/licenses/.
-= END original header =-
diff -durN gmp-4.2.4.orig/mpz/perfpow.c gmp-4.2.4/mpz/perfpow.c
--- gmp-4.2.4.orig/mpz/perfpow.c 2007-08-30 20:31:41.000000000 +0200
+++ gmp-4.2.4/mpz/perfpow.c 2009-03-08 18:36:16.000000000 +0100
@@ -1,7 +1,7 @@
/* mpz_perfect_power_p(arg) -- Return non-zero if ARG is a perfect power,
zero otherwise.
-Copyright 1998, 1999, 2000, 2001, 2005 Free Software Foundation, Inc.
+Copyright 1998, 1999, 2000, 2001, 2005, 2008 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
@@ -59,6 +59,8 @@
#define SMALLEST_OMITTED_PRIME 1009
+#define POW2P(a) (((a) & ((a) - 1)) == 0)
+
int
mpz_perfect_power_p (mpz_srcptr u)
{
@@ -72,16 +74,13 @@
mp_size_t usize = SIZ (u);
TMP_DECL;
- if (usize == 0)
- return 1; /* consider 0 a perfect power */
+ if (mpz_cmpabs_ui (u, 1) <= 0)
+ return 1; /* -1, 0, and +1 are perfect powers */
n2 = mpz_scan1 (u, 0);
if (n2 == 1)
return 0; /* 2 divides exactly once. */
- if (n2 != 0 && (n2 & 1) == 0 && usize < 0)
- return 0; /* 2 has even multiplicity with negative U */
-
TMP_MARK;
uns = ABS (usize) - n2 / BITS_PER_MP_LIMB;
@@ -89,6 +88,14 @@
MPZ_TMP_INIT (u2, uns);
mpz_tdiv_q_2exp (u2, u, n2);
+ mpz_abs (u2, u2);
+
+ if (mpz_cmp_ui (u2, 1) == 0)
+ {
+ TMP_FREE;
+ /* factoring completed; consistent power */
+ return ! (usize < 0 && POW2P(n2));
+ }
if (isprime (n2))
goto n2prime;
@@ -97,6 +104,9 @@
{
prime = primes[i];
+ if (mpz_cmp_ui (u2, prime) < 0)
+ break;
+
if (mpz_divisible_ui_p (u2, prime)) /* divisible by this prime? */
{
rem = mpz_tdiv_q_ui (q, u2, prime * prime);
@@ -115,12 +125,6 @@
n++;
}
- if ((n & 1) == 0 && usize < 0)
- {
- TMP_FREE;
- return 0; /* even multiplicity with negative U, reject */
- }
-
n2 = gcd (n2, n);
if (n2 == 1)
{
@@ -128,10 +132,11 @@
return 0; /* we have multiplicity 1 of some factor */
}
- if (mpz_cmpabs_ui (u2, 1) == 0)
+ if (mpz_cmp_ui (u2, 1) == 0)
{
TMP_FREE;
- return 1; /* factoring completed; consistent power */
+ /* factoring completed; consistent power */
+ return ! (usize < 0 && POW2P(n2));
}
/* As soon as n2 becomes a prime number, stop factoring.
@@ -169,6 +174,10 @@
else
{
unsigned long int nth;
+
+ if (usize < 0 && POW2P(n2))
+ return 0;
+
/* We found some factors above. We just need to consider values of n
that divides n2. */
for (nth = 2; nth <= n2; nth++)
@@ -184,8 +193,11 @@
exact = mpz_root (q, u2, nth);
if (exact)
{
- TMP_FREE;
- return 1;
+ if (! (usize < 0 && POW2P(nth)))
+ {
+ TMP_FREE;
+ return 1;
+ }
}
if (mpz_cmp_ui (q, SMALLEST_OMITTED_PRIME) < 0)
{
@@ -199,6 +211,9 @@
}
n2prime:
+ if (usize < 0 && POW2P(n2))
+ return 0;
+
exact = mpz_root (NULL, u2, n2);
TMP_FREE;
return exact;
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