134 lines
3.4 KiB
C
134 lines
3.4 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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Copyright (C) 2011 Fredrik Johansson
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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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#include "fmpq_poly.h"
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void
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_fmpq_poly_invsqrt_series(fmpz * rpoly, fmpz_t rden,
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const fmpz * poly, const fmpz_t den, slong n)
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{
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slong m;
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fmpz * t, * u;
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fmpz_t tden, uden;
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if (n == 1)
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{
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fmpz_one(rpoly);
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fmpz_one(rden);
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return;
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}
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m = (n + 1) / 2;
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_fmpq_poly_invsqrt_series(rpoly, rden, poly, den, m);
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fmpz_init(tden);
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fmpz_init(uden);
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t = _fmpz_vec_init(n);
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u = _fmpz_vec_init(n);
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_fmpz_vec_zero(rpoly + m, n - m);
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_fmpq_poly_mul(t, tden, rpoly, rden, m, rpoly, rden, m);
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if (2*m - 1 < n)
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fmpz_zero(t + n - 1);
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_fmpq_poly_mullow(u, uden, t, tden, n, rpoly, rden, n, n);
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_fmpq_poly_mullow(t, tden, u, uden, n, poly, den, n, n);
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_fmpz_vec_neg(t + m, t + m, n - m);
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_fmpz_vec_zero(t, m);
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fmpz_mul_ui(tden, tden, UWORD(2));
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_fmpq_poly_canonicalise(t, tden, n);
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_fmpq_poly_add(rpoly, rden, rpoly, rden, m, t, tden, n);
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fmpz_clear(tden);
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fmpz_clear(uden);
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_fmpz_vec_clear(t, n);
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_fmpz_vec_clear(u, n);
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}
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void fmpq_poly_invsqrt_series(fmpq_poly_t res, const fmpq_poly_t poly, slong n)
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{
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fmpz *copy;
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int alloc;
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if (poly->length < 1 || !fmpz_equal(poly->coeffs, poly->den))
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{
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flint_printf("Exception (fmpq_poly_invsqrt_series). Constant term != 1.\n");
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abort();
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}
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if (n < 1)
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{
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fmpq_poly_zero(res);
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return;
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}
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if (poly->length >= n)
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{
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copy = poly->coeffs;
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alloc = 0;
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}
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else
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{
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slong i;
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copy = (fmpz *) flint_malloc(n * sizeof(fmpz));
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for (i = 0; i < poly->length; i++)
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copy[i] = poly->coeffs[i];
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for ( ; i < n; i++)
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copy[i] = 0;
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alloc = 1;
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}
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if (res != poly)
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{
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fmpq_poly_fit_length(res, n);
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_fmpq_poly_invsqrt_series(res->coeffs, res->den, copy, poly->den, n);
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}
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else
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{
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fmpq_poly_t t;
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fmpq_poly_init2(t, n);
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_fmpq_poly_invsqrt_series(t->coeffs, t->den, copy, poly->den, n);
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fmpq_poly_swap(res, t);
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fmpq_poly_clear(t);
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}
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_fmpq_poly_set_length(res, n);
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fmpq_poly_canonicalise(res);
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if (alloc)
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flint_free(copy);
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}
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