108 lines
3.5 KiB
C
108 lines
3.5 KiB
C
/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2009 William Hart
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******************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <gmp.h>
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#include "flint.h"
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#include "ulong_extras.h"
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#include "fmpz.h"
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void
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fmpz_fdiv_qr(fmpz_t f, fmpz_t s, const fmpz_t g, const fmpz_t h)
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{
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fmpz c1 = *g;
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fmpz c2 = *h;
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if (fmpz_is_zero(h))
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{
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flint_printf("Exception (fmpz_fdiv_q). Division by zero.\n");
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abort();
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}
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if (!COEFF_IS_MPZ(c1)) /* g is small */
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{
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if (!COEFF_IS_MPZ(c2)) /* h is also small */
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{
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fmpz q = c1 / c2; /* compute C quotient */
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fmpz r = c1 - c2 * q; /* compute remainder */
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if ((c2 > WORD(0) && r < WORD(0)) || (c2 < WORD(0) && r > WORD(0)))
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{
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q--; /* q cannot overflow as remainder implies |c2| != 1 */
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r += c2;
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}
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fmpz_set_si(f, q);
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fmpz_set_si(s, r);
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}
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else /* h is large and g is small */
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{
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if (c1 == WORD(0))
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{
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fmpz_set_ui(f, WORD(0)); /* g is zero */
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fmpz_set_si(s, c1);
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}
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else if ((c1 < WORD(0) && fmpz_sgn(h) < 0) || (c1 > WORD(0) && fmpz_sgn(h) > 0)) /* signs are the same */
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{
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fmpz_zero(f); /* quotient is positive, round down to zero */
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fmpz_set_si(s, c1);
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}
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else
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{
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fmpz_add(s, g, h);
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fmpz_set_si(f, WORD(-1)); /* quotient is negative, round down to minus one */
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}
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}
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}
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else /* g is large */
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{
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__mpz_struct *mpz_ptr, *mpz_ptr2;
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_fmpz_promote(f); /* must not hang on to ptr whilst promoting s */
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mpz_ptr2 = _fmpz_promote(s);
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mpz_ptr = COEFF_TO_PTR(*f);
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if (!COEFF_IS_MPZ(c2)) /* h is small */
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{
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if (c2 > 0) /* h > 0 */
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{
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flint_mpz_fdiv_qr_ui(mpz_ptr, mpz_ptr2, COEFF_TO_PTR(c1), c2);
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}
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else
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{
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flint_mpz_cdiv_qr_ui(mpz_ptr, mpz_ptr2, COEFF_TO_PTR(c1), -c2);
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mpz_neg(mpz_ptr, mpz_ptr);
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}
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}
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else /* both are large */
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{
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mpz_fdiv_qr(mpz_ptr, mpz_ptr2, COEFF_TO_PTR(c1), COEFF_TO_PTR(c2));
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}
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_fmpz_demote_val(f); /* division by h may result in small value */
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_fmpz_demote_val(s); /* division by h may result in small value */
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}
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}
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