66 lines
2.1 KiB
C
66 lines
2.1 KiB
C
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/*=============================================================================
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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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Copyright (C) 2011 Sebastian Pancratz
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******************************************************************************/
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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 fmpz_fdiv_r_2exp(fmpz_t f, const fmpz_t g, ulong exp)
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{
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fmpz d = *g;
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if (!COEFF_IS_MPZ(d)) /* g is small */
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{
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if (d >= 0)
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{
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fmpz_set_ui(f, exp < (FLINT_BITS - 2) ? d & ((WORD(1) << exp) - 1) : d);
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}
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else
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{
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if (exp <= FLINT_BITS - 2)
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{
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fmpz_set_ui(f, d & ((WORD(1) << exp) - 1));
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}
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else
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{
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__mpz_struct * mpz_ptr = _fmpz_promote(f);
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flint_mpz_set_ui(mpz_ptr, 1);
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mpz_mul_2exp(mpz_ptr, mpz_ptr, exp);
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flint_mpz_sub_ui(mpz_ptr, mpz_ptr, -d);
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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 = _fmpz_promote(f); /* g is already large */
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mpz_fdiv_r_2exp(mpz_ptr, COEFF_TO_PTR(d), exp);
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_fmpz_demote_val(f); /* division may make value small */
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}
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}
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