87 lines
2.2 KiB
C
87 lines
2.2 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 Fredrik Johansson
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "nmod_vec.h"
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#include "nmod_poly.h"
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mp_limb_t
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_nmod_poly_div_root(mp_ptr Q, mp_srcptr A, slong len, mp_limb_t c, nmod_t mod)
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{
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mp_limb_t r, t;
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slong i;
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if (len < 2)
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return UWORD(0);
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t = A[len - 2];
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r = Q[len - 2] = A[len - 1];
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for (i = len - 2; i > 0; i--)
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{
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r = nmod_add(nmod_mul(r, c, mod), t, mod);
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t = A[i-1];
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Q[i-1] = r;
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}
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r = nmod_add(nmod_mul(r, c, mod), t, mod);
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return r;
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}
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mp_limb_t
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nmod_poly_div_root(nmod_poly_t Q,
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const nmod_poly_t A, mp_limb_t c)
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{
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mp_limb_t rem;
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slong len = A->length;
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if (len == 0)
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{
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nmod_poly_zero(Q);
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return UWORD(0);
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}
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if (len == 1)
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{
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rem = A->coeffs[0];
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nmod_poly_zero(Q);
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return rem;
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}
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if (c == 0)
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{
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rem = A->coeffs[0];
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nmod_poly_shift_right(Q, A, 1);
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return rem;
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}
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nmod_poly_fit_length(Q, len - 1);
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rem = _nmod_poly_div_root(Q->coeffs, A->coeffs, len, c, Q->mod);
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Q->length = len - 1;
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return rem;
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}
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