mirror of
https://github.com/vale981/arb
synced 2025-03-04 17:01:40 -05:00
117 lines
3.3 KiB
C
117 lines
3.3 KiB
C
/*
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Copyright (C) 2008, 2009 William Hart
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Copyright (C) 2011 Sebastian Pancratz
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Copyright (C) 2012 Fredrik Johansson
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This file is part of Arb.
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Arb is free software: you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License (LGPL) as published
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by the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version. See <http://www.gnu.org/licenses/>.
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*/
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#include "arb_poly.h"
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void
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_arb_poly_mullow_classical(arb_ptr res,
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arb_srcptr poly1, slong len1,
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arb_srcptr poly2, slong len2, slong n, slong prec)
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{
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len1 = FLINT_MIN(len1, n);
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len2 = FLINT_MIN(len2, n);
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if (n == 1)
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{
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arb_mul(res, poly1, poly2, prec);
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}
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else if (poly1 == poly2 && len1 == len2)
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{
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slong i, start, stop;
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arb_sqr(res, poly1, prec);
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arb_mul(res + 1, poly1, poly1 + 1, prec);
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arb_mul_2exp_si(res + 1, res + 1, 1);
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for (i = 2; i < FLINT_MIN(n, 2 * len1 - 3); i++)
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{
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start = FLINT_MAX(0, i - len1 + 1);
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stop = FLINT_MIN(len1 - 1, (i + 1) / 2 - 1);
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arb_dot(res + i, NULL, 0, poly1 + start, 1,
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poly1 + i - start, -1, stop - start + 1, prec);
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arb_mul_2exp_si(res + i, res + i, 1);
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if (i % 2 == 0 && i / 2 < len1)
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arb_addmul(res + i, poly1 + i / 2, poly1 + i / 2, prec);
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}
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if (len1 > 2 && n >= 2 * len1 - 2)
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{
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arb_mul(res + 2 * len1 - 3, poly1 + len1 - 1, poly1 + len1 - 2, prec);
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arb_mul_2exp_si(res + 2 * len1 - 3, res + 2 * len1 - 3, 1);
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}
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if (n >= 2 * len1 - 1)
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arb_sqr(res + 2 * len1 - 2, poly1 + len1 - 1, prec);
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}
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else if (len1 == 1)
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{
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_arb_vec_scalar_mul(res, poly2, n, poly1, prec);
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}
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else if (len2 == 1)
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{
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_arb_vec_scalar_mul(res, poly1, n, poly2, prec);
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}
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else
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{
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slong i, top1, top2;
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arb_mul(res, poly1, poly2, prec);
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for (i = 1; i < n; i++)
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{
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top1 = FLINT_MIN(len1 - 1, i);
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top2 = FLINT_MIN(len2 - 1, i);
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arb_dot(res + i, NULL, 0, poly1 + i - top2, 1,
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poly2 + top2, -1, top1 + top2 - i + 1, prec);
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}
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}
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}
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void
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arb_poly_mullow_classical(arb_poly_t res, const arb_poly_t poly1,
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const arb_poly_t poly2,
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slong n, slong prec)
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{
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slong len_out;
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if (poly1->length == 0 || poly2->length == 0 || n == 0)
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{
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arb_poly_zero(res);
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return;
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}
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len_out = poly1->length + poly2->length - 1;
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if (n > len_out)
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n = len_out;
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if (res == poly1 || res == poly2)
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{
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arb_poly_t t;
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arb_poly_init2(t, n);
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_arb_poly_mullow_classical(t->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length, n, prec);
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arb_poly_swap(res, t);
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arb_poly_clear(t);
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}
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else
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{
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arb_poly_fit_length(res, n);
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_arb_poly_mullow_classical(res->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length, n, prec);
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}
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_arb_poly_set_length(res, n);
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_arb_poly_normalise(res);
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}
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