95 lines
2.4 KiB
C
95 lines
2.4 KiB
C
/* mpz_remove -- divide out a factor and return its multiplicity.
|
|
|
|
Copyright 1998, 1999, 2000, 2001, 2002 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 2.1 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; see the file COPYING.LIB. If not, write to
|
|
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
|
|
MA 02110-1301, USA. */
|
|
|
|
#include "mpir.h"
|
|
#include "gmp-impl.h"
|
|
|
|
mp_bitcnt_t
|
|
mpz_remove (mpz_ptr dest, mpz_srcptr src, mpz_srcptr f)
|
|
{
|
|
mpz_t fpow[40]; /* inexhaustible...until year 2020 or so */
|
|
mpz_t x, rem;
|
|
mp_bitcnt_t pwr;
|
|
int p;
|
|
|
|
if (mpz_cmp_ui (f, 1) <= 0)
|
|
DIVIDE_BY_ZERO;
|
|
|
|
if (SIZ (src) == 0)
|
|
{
|
|
if (src != dest)
|
|
mpz_set (dest, src);
|
|
return 0;
|
|
}
|
|
|
|
if (mpz_cmp_ui (f, 2) == 0)
|
|
{
|
|
unsigned long int s0;
|
|
s0 = mpz_scan1 (src, 0);
|
|
mpz_fdiv_q_2exp (dest, src, s0);
|
|
return s0;
|
|
}
|
|
|
|
/* We could perhaps compute mpz_scan1(src,0)/mpz_scan1(f,0). It is an
|
|
upper bound of the result we're seeking. We could also shift down the
|
|
operands so that they become odd, to make intermediate values smaller. */
|
|
|
|
mpz_init (rem);
|
|
mpz_init (x);
|
|
|
|
pwr = 0;
|
|
mpz_init (fpow[0]);
|
|
mpz_set (fpow[0], f);
|
|
mpz_set (dest, src);
|
|
|
|
/* Divide by f, f^2, ..., f^(2^k) until we get a remainder for f^(2^k). */
|
|
for (p = 0;; p++)
|
|
{
|
|
mpz_tdiv_qr (x, rem, dest, fpow[p]);
|
|
if (SIZ (rem) != 0)
|
|
break;
|
|
mpz_init (fpow[p + 1]);
|
|
mpz_mul (fpow[p + 1], fpow[p], fpow[p]);
|
|
mpz_set (dest, x);
|
|
}
|
|
|
|
pwr = (1 << p) - 1;
|
|
|
|
mpz_clear (fpow[p]);
|
|
|
|
/* Divide by f^(2^(k-1)), f^(2^(k-2)), ..., f for all divisors that give a
|
|
zero remainder. */
|
|
while (--p >= 0)
|
|
{
|
|
mpz_tdiv_qr (x, rem, dest, fpow[p]);
|
|
if (SIZ (rem) == 0)
|
|
{
|
|
pwr += 1 << p;
|
|
mpz_set (dest, x);
|
|
}
|
|
mpz_clear (fpow[p]);
|
|
}
|
|
|
|
mpz_clear (x);
|
|
mpz_clear (rem);
|
|
return pwr;
|
|
}
|