157 lines
4.2 KiB
C
157 lines
4.2 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) 2010 Sebastian Pancratz
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******************************************************************************/
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#include <stdlib.h>
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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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void
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_fmpz_poly_pseudo_divrem_cohen(fmpz * Q, fmpz * R, const fmpz * A,
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slong lenA, const fmpz * B, slong lenB)
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{
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const fmpz * leadB = B + (lenB - 1);
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slong e, lenQ;
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fmpz_t pow;
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if (lenB == 1)
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{
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fmpz_init(pow);
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fmpz_pow_ui(pow, leadB, lenA - 1);
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_fmpz_vec_scalar_mul_fmpz(Q, A, lenA, pow);
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_fmpz_vec_zero(R, lenA);
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fmpz_clear(pow);
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return;
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}
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lenQ = lenA - lenB + 1;
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_fmpz_vec_zero(Q, lenQ);
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if (R != A)
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_fmpz_vec_set(R, A, lenA);
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e = lenA - lenB;
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/* Unroll the first run of the while loop */
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{
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fmpz_set(Q + (lenQ - 1), R + (lenA - 1));
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_fmpz_vec_scalar_mul_fmpz(R, R, lenA - 1, leadB);
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_fmpz_vec_scalar_submul_fmpz(R + (lenA - lenB), B, lenB - 1, R + (lenA - 1));
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fmpz_zero(R + (lenA - 1));
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lenA--;
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FMPZ_VEC_NORM(R, lenA);
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}
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while (lenA >= lenB)
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{
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_fmpz_vec_scalar_mul_fmpz(Q, Q, lenQ, leadB);
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fmpz_add(Q + (lenA - lenB), Q + (lenA - lenB), R + (lenA - 1));
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_fmpz_vec_scalar_mul_fmpz(R, R, lenA - 1, leadB);
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_fmpz_vec_scalar_submul_fmpz(R + lenA - lenB, B, lenB - 1, R + (lenA - 1));
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fmpz_zero(R + (lenA - 1));
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lenA--;
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FMPZ_VEC_NORM(R, lenA);
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e--;
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}
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fmpz_init(pow);
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fmpz_pow_ui(pow, leadB, e);
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_fmpz_vec_scalar_mul_fmpz(Q, Q, lenQ, pow);
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_fmpz_vec_scalar_mul_fmpz(R, R, lenA, pow);
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fmpz_clear(pow);
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}
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void
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fmpz_poly_pseudo_divrem_cohen(fmpz_poly_t Q, fmpz_poly_t R,
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const fmpz_poly_t A, const fmpz_poly_t B)
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{
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slong lenq, lenr;
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fmpz *q, *r;
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if (B->length == 0)
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{
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flint_printf("Exception (fmpz_poly_pseudo_divrem_cohen). Division by zero.\n");
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abort();
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}
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if (Q == R)
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{
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flint_printf("Exception (fmpz_poly_pseudo_divrem_cohen). \n"
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"Output arguments Q and R may not be aliased.\n");
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abort();
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}
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if (A->length < B->length)
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{
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fmpz_poly_zero(Q);
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fmpz_poly_set(R, A);
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return;
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}
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lenq = A->length - B->length + 1;
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lenr = A->length;
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if ((Q == A) || (Q == B))
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q = _fmpz_vec_init(lenq);
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else
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{
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fmpz_poly_fit_length(Q, lenq);
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q = Q->coeffs;
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}
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if (R == B)
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r = _fmpz_vec_init(lenr);
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else
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{
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fmpz_poly_fit_length(R, lenr);
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r = R->coeffs;
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}
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_fmpz_poly_pseudo_divrem_cohen(q, r, A->coeffs, A->length, B->coeffs, B->length);
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for (lenr = B->length - 1; (lenr >= 0) && r[lenr] == WORD(0); lenr--) ;
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lenr++;
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if ((Q == A) || (Q == B))
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{
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_fmpz_vec_clear(Q->coeffs, Q->alloc);
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Q->coeffs = q;
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Q->alloc = lenq;
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Q->length = lenq;
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}
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else
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_fmpz_poly_set_length(Q, lenq);
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if (R == B)
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{
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_fmpz_vec_clear(R->coeffs, R->alloc);
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R->coeffs = r;
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R->alloc = A->length;
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R->length = lenr;
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}
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else
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_fmpz_poly_set_length(R, lenr);
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}
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