105 lines
2.9 KiB
C
105 lines
2.9 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) 2013 William Hart
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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_poly.h"
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void
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_fmpz_poly_div_preinv(fmpz * Q, const fmpz * A, slong len1_in,
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const fmpz * B, const fmpz * B_inv, slong len2)
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{
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slong len1 = len1_in;
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slong n = len1 - len2 + 1;
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fmpz * A_rev;
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fmpz * a;
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if (n > len2)
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{
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a = _fmpz_vec_init(len1_in);
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_fmpz_vec_set(a, A, len1_in);
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do {
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slong start = n - len2;
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_fmpz_poly_divrem_preinv(Q + start, a + start, len1 - start,
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B, B_inv, len2);
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n -= len2;
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len1 -= len2;
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} while (n > len2);
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} else
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a = (fmpz *) A;
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A_rev = _fmpz_vec_init(len1);
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_fmpz_poly_reverse(A_rev, a, len1, len1);
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_fmpz_poly_mullow(Q, A_rev, len1, B_inv, len2, n);
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_fmpz_poly_reverse(Q, Q, n, n);
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if (a != A)
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_fmpz_vec_clear(a, len1_in);
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_fmpz_vec_clear(A_rev, len1);
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}
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void
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fmpz_poly_div_preinv(fmpz_poly_t Q, const fmpz_poly_t A,
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const fmpz_poly_t B, const fmpz_poly_t B_inv)
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{
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fmpz_poly_t tQ;
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fmpz *q;
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slong len1 = A->length, len2 = B_inv->length;
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slong qlen = len1 - len2 + 1;
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if (len1 < len2)
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{
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fmpz_poly_zero(Q);
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return;
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}
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if (Q == A || Q == B || Q == B_inv)
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{
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fmpz_poly_init2(tQ, qlen);
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q = tQ->coeffs;
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}
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else
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{
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fmpz_poly_fit_length(Q, qlen);
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q = Q->coeffs;
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}
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_fmpz_poly_div_preinv(q, A->coeffs, len1, B->coeffs, B_inv->coeffs, len2);
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if (Q == A || Q == B || Q == B_inv)
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{
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_fmpz_poly_set_length(tQ, qlen);
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fmpz_poly_swap(tQ, Q);
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fmpz_poly_clear(tQ);
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}
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else
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_fmpz_poly_set_length(Q, qlen);
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/* no need to normalise */
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}
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