92 lines
2.6 KiB
C
92 lines
2.6 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) 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 "fmpz.h"
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#include "fmpz_vec.h"
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#include "fmpz_poly.h"
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/*
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Assumes len > 0 and 0 < n <= 2 * len - 1.
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*/
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void _fmpz_poly_sqrlow_classical(fmpz *rop, const fmpz *op, slong len, slong n)
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{
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if (len == 1 || n == 1) /* Special case */
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{
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fmpz_mul(rop, op, op);
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}
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else /* Ordinary case */
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{
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slong i;
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_fmpz_vec_scalar_mul_fmpz(rop, op, FLINT_MIN(len, n), op);
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_fmpz_vec_scalar_mul_fmpz(rop + len, op + 1, n - len, op + len - 1);
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for (i = 1; i < len - 1; i++)
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_fmpz_vec_scalar_addmul_fmpz(rop + i + 1,
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op + 1, FLINT_MIN(i - 1, n - (i + 1)), op + i);
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for (i = 1; i < FLINT_MIN(2 * len - 2, n); i++)
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fmpz_mul_ui(rop + i, rop + i, 2);
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for (i = 1; i < FLINT_MIN(len - 1, (n + 1) / 2); i++)
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fmpz_addmul(rop + 2 * i, op + i, op + i);
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}
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}
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void
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fmpz_poly_sqrlow_classical(fmpz_poly_t res, const fmpz_poly_t poly, slong n)
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{
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slong len = poly->length;
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if (len == 0 || n == 0)
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{
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fmpz_poly_zero(res);
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return;
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}
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n = FLINT_MIN(2 * len - 1, n);
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if (res == poly)
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{
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fmpz_poly_t t;
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fmpz_poly_init2(t, n);
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_fmpz_poly_sqrlow_classical(t->coeffs, poly->coeffs, len, n);
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fmpz_poly_swap(res, t);
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fmpz_poly_clear(t);
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}
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else
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{
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fmpz_poly_fit_length(res, n);
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_fmpz_poly_sqrlow_classical(res->coeffs, poly->coeffs, len, n);
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}
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_fmpz_poly_set_length(res, n);
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_fmpz_poly_normalise(res);
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}
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