88 lines
2.3 KiB
C
88 lines
2.3 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) 2012 Fredrik Johansson
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******************************************************************************/
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#include "fmpz_poly.h"
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/* quotient of absolute value, rounded up */
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static __inline__ void
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fmpz_cdiv_abs_q(fmpz_t q, const fmpz_t x, const fmpz_t y)
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{
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if (fmpz_sgn(x) == fmpz_sgn(y))
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{
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fmpz_cdiv_q(q, x, y);
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}
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else
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{
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fmpz_fdiv_q(q, x, y);
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fmpz_neg(q, q);
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}
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}
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void
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_fmpz_poly_bound_roots(fmpz_t bound, const fmpz * poly, slong len)
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{
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if (len <= 1)
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{
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fmpz_zero(bound);
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}
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else if (len == 2)
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{
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fmpz_cdiv_abs_q(bound, poly + 0, poly + 1);
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}
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else
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{
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slong i;
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fmpz_t t;
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fmpz_init(t);
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fmpz_mul_2exp(t, poly + len - 1, 1);
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fmpz_cdiv_abs_q(bound, poly + 0, t);
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fmpz_root(bound, bound, len - 1);
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for (i = 1; i < len - 1; i++)
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{
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fmpz_cdiv_abs_q(t, poly + len - i - 1, poly + len - 1);
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fmpz_root(t, t, i);
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fmpz_add_ui(t, t, 1);
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if (fmpz_cmp(t, bound) > 0)
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fmpz_swap(t, bound);
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}
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fmpz_mul_2exp(bound, bound, 1);
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fmpz_clear(t);
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}
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}
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void
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fmpz_poly_bound_roots(fmpz_t bound, const fmpz_poly_t poly)
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{
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_fmpz_poly_bound_roots(bound, poly->coeffs, poly->length);
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}
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