mirror of
https://github.com/vale981/arb
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80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/*
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Copyright (C) 2013 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_sqrt_series(arb_ptr g,
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arb_srcptr h, slong hlen, slong len, slong prec)
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{
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hlen = FLINT_MIN(hlen, len);
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while (hlen > 0 && arb_is_zero(h + hlen - 1))
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hlen--;
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if (hlen <= 1)
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{
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arb_sqrt(g, h, prec);
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_arb_vec_zero(g + 1, len - 1);
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}
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else if (len == 2)
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{
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arb_sqrt(g, h, prec);
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arb_div(g + 1, h + 1, h, prec);
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arb_mul(g + 1, g + 1, g, prec);
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arb_mul_2exp_si(g + 1, g + 1, -1);
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}
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else if (_arb_vec_is_zero(h + 1, hlen - 2))
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{
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arb_t t;
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arb_init(t);
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arf_set_si_2exp_si(arb_midref(t), 1, -1);
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_arb_poly_binomial_pow_arb_series(g, h, hlen, t, len, prec);
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arb_clear(t);
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}
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else
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{
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arb_ptr t;
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t = _arb_vec_init(len);
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_arb_poly_rsqrt_series(t, h, hlen, len, prec);
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_arb_poly_mullow(g, t, len, h, hlen, len, prec);
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_arb_vec_clear(t, len);
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}
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}
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void
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arb_poly_sqrt_series(arb_poly_t g, const arb_poly_t h, slong n, slong prec)
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{
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if (n == 0)
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{
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arb_poly_zero(g);
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return;
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}
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if (g == h)
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{
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arb_poly_t t;
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arb_poly_init(t);
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arb_poly_sqrt_series(t, h, n, prec);
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arb_poly_swap(g, t);
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arb_poly_clear(t);
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return;
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}
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arb_poly_fit_length(g, n);
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if (h->length == 0)
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_arb_vec_indeterminate(g->coeffs, n);
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else
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_arb_poly_sqrt_series(g->coeffs, h->coeffs, h->length, n, prec);
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_arb_poly_set_length(g, n);
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_arb_poly_normalise(g);
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}
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