80 lines
2.4 KiB
C
80 lines
2.4 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) 2011 Fredrik Johansson
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******************************************************************************/
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#include "nmod_poly.h"
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#include "ulong_extras.h"
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void
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_nmod_poly_product_roots_nmod_vec(mp_ptr poly, mp_srcptr xs, slong n, nmod_t mod)
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{
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if (n == 0)
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{
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poly[0] = UWORD(1);
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}
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else if (n < 20)
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{
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slong i, j;
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poly[n] = UWORD(1);
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poly[n - 1] = nmod_neg(xs[0], mod);
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for (i = 1; i < n; i++)
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{
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poly[n-i-1] = nmod_neg(n_mulmod2_preinv(poly[n-i], xs[i],
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mod.n, mod.ninv), mod);
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for (j = 0; j < i - 1; j++)
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{
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poly[n-i+j] = nmod_sub(poly[n-i+j],
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n_mulmod2_preinv(poly[n-i+j+1], xs[i], mod.n, mod.ninv),
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mod);
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}
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poly[n-1] = nmod_sub(poly[n-1], xs[i], mod);
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}
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}
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else
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{
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const slong m = (n + 1) / 2;
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mp_ptr tmp;
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tmp = _nmod_vec_init(n + 2);
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_nmod_poly_product_roots_nmod_vec(tmp, xs, m, mod);
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_nmod_poly_product_roots_nmod_vec(tmp + m + 1, xs + m, n - m, mod);
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_nmod_poly_mul(poly, tmp, m + 1, tmp + m + 1, n - m + 1, mod);
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_nmod_vec_clear(tmp);
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}
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}
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void
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nmod_poly_product_roots_nmod_vec(nmod_poly_t poly, mp_srcptr xs, slong n)
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{
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nmod_poly_fit_length(poly, n + 1);
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_nmod_poly_product_roots_nmod_vec(poly->coeffs, xs, n, poly->mod);
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poly->length = n + 1;
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}
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