mirror of
https://github.com/vale981/arb
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55 lines
1.4 KiB
C
55 lines
1.4 KiB
C
/*
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Copyright (C) 2011 William Hart
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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_product_roots(arb_ptr poly, arb_srcptr xs, slong n, slong prec)
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{
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if (n == 0)
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{
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arb_one(poly);
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}
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else if (n == 1)
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{
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arb_neg(poly, xs);
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arb_one(poly + 1);
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}
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else if (n == 2)
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{
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arb_mul(poly, xs + 0, xs + 1, prec);
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arb_add(poly + 1, xs + 0, xs + 1, prec);
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arb_neg(poly + 1, poly + 1);
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arb_one(poly + 2);
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}
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else
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{
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const slong m = (n + 1) / 2;
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arb_ptr tmp;
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tmp = _arb_vec_init(n + 2);
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_arb_poly_product_roots(tmp, xs, m, prec);
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_arb_poly_product_roots(tmp + m + 1, xs + m, n - m, prec);
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_arb_poly_mul_monic(poly, tmp, m + 1, tmp + m + 1, n - m + 1, prec);
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_arb_vec_clear(tmp, n + 2);
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}
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}
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void
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arb_poly_product_roots(arb_poly_t poly, arb_srcptr xs, slong n, slong prec)
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{
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arb_poly_fit_length(poly, n + 1);
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_arb_poly_product_roots(poly->coeffs, xs, n, prec);
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_arb_poly_set_length(poly, n + 1);
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}
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