Annotation of OpenXM_contrib/gmp/mpz/remove.c, Revision 1.1
1.1 ! maekawa 1: /* mpz_remove -- divide out a factor and return its multiplicity.
! 2:
! 3: Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
! 4:
! 5: This file is part of the GNU MP Library.
! 6:
! 7: The GNU MP Library is free software; you can redistribute it and/or modify
! 8: it under the terms of the GNU Lesser General Public License as published by
! 9: the Free Software Foundation; either version 2.1 of the License, or (at your
! 10: option) any later version.
! 11:
! 12: The GNU MP Library is distributed in the hope that it will be useful, but
! 13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
! 14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
! 15: License for more details.
! 16:
! 17: You should have received a copy of the GNU Lesser General Public License
! 18: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
! 19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
! 20: MA 02111-1307, USA. */
! 21:
! 22: #include "gmp.h"
! 23: #include "gmp-impl.h"
! 24:
! 25: unsigned long int
! 26: #if __STDC__
! 27: mpz_remove (mpz_ptr dest, mpz_srcptr src, mpz_srcptr f)
! 28: #else
! 29: mpz_remove (dest, src, f)
! 30: mpz_ptr dest;
! 31: mpz_srcptr src;
! 32: mpz_srcptr f;
! 33: #endif
! 34: {
! 35: mpz_t fpow[40]; /* inexhaustible...until year 2020 or so */
! 36: mpz_t x, rem;
! 37: unsigned long int pwr;
! 38: int p;
! 39:
! 40: if (mpz_cmp_ui (f, 1) <= 0 || mpz_sgn (src) == 0)
! 41: DIVIDE_BY_ZERO;
! 42: if (mpz_cmp_ui (f, 2) == 0)
! 43: {
! 44: unsigned long int s0;
! 45: s0 = mpz_scan1 (src, 0);
! 46: mpz_div_2exp (dest, src, s0);
! 47: return s0;
! 48: }
! 49:
! 50: /* We could perhaps compute mpz_scan1(src,0)/mpz_scan1(f,0). It is an
! 51: upper bound of the result we're seeking. We could also shift down the
! 52: operands so that they become odd, to make intermediate values smaller. */
! 53:
! 54: mpz_init (rem);
! 55: mpz_init (x);
! 56:
! 57: pwr = 0;
! 58: mpz_init (fpow[0]);
! 59: mpz_set (fpow[0], f);
! 60: mpz_set (dest, src);
! 61:
! 62: /* Divide by f, f^2, ..., f^(2^k) until we get a remainder for f^(2^k). */
! 63: for (p = 0;; p++)
! 64: {
! 65: mpz_tdiv_qr (x, rem, dest, fpow[p]);
! 66: if (SIZ (rem) != 0)
! 67: break;
! 68: mpz_init (fpow[p + 1]);
! 69: mpz_mul (fpow[p + 1], fpow[p], fpow[p]);
! 70: mpz_set (dest, x);
! 71: }
! 72:
! 73: pwr = (1 << p) - 1;
! 74:
! 75: mpz_clear (fpow[p]);
! 76:
! 77: /* Divide by f^(2^(k-1)), f^(2^(k-2)), ..., f for all divisors that give a
! 78: zero remainder. */
! 79: while (--p >= 0)
! 80: {
! 81: mpz_tdiv_qr (x, rem, dest, fpow[p]);
! 82: if (SIZ (rem) == 0)
! 83: {
! 84: pwr += 1 << p;
! 85: mpz_set (dest, x);
! 86: }
! 87: mpz_clear (fpow[p]);
! 88: }
! 89:
! 90: mpz_clear (x);
! 91: mpz_clear (rem);
! 92: return pwr;
! 93: }
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>