mirror of
https://github.com/vale981/arb
synced 2025-03-06 01:41:39 -05:00
98 lines
2.7 KiB
C
98 lines
2.7 KiB
C
/*=============================================================================
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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
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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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ARB 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 ARB; 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) 2013 Fredrik Johansson
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******************************************************************************/
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#include "fmprb_poly.h"
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void
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_fmprb_poly_rsqrt_series(fmprb_ptr g,
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fmprb_srcptr h, long hlen, long len, long prec)
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{
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hlen = FLINT_MIN(hlen, len);
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fmprb_rsqrt(g, h, prec);
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if (hlen == 1)
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{
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_fmprb_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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fmprb_div(g + 1, h + 1, h, prec);
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fmprb_mul(g + 1, g + 1, g, prec);
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fmprb_mul_2exp_si(g + 1, g + 1, -1);
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fmprb_neg(g + 1, g + 1);
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}
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else
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{
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fmprb_ptr t, u;
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long tlen;
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t = _fmprb_vec_init(2 * len);
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u = t + len;
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NEWTON_INIT(1, len)
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NEWTON_LOOP(m, n)
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tlen = FLINT_MIN(2 * m - 1, n);
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_fmprb_poly_mullow(t, g, m, g, m, tlen, prec);
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_fmprb_poly_mullow(u, g, m, t, tlen, n, prec);
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_fmprb_poly_mullow(t, u, n, h, hlen, n, prec);
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_fmprb_vec_scalar_mul_2exp_si(g + m, t + m, n - m, -1);
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_fmprb_vec_neg(g + m, g + m, n - m);
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NEWTON_END_LOOP
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NEWTON_END
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_fmprb_vec_clear(t, 2 * len);
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}
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}
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void
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fmprb_poly_rsqrt_series(fmprb_poly_t g, const fmprb_poly_t h, long n, long prec)
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{
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if (n == 0)
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{
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fmprb_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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fmprb_poly_t t;
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fmprb_poly_init(t);
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fmprb_poly_rsqrt_series(t, h, n, prec);
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fmprb_poly_swap(g, t);
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fmprb_poly_clear(t);
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return;
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}
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fmprb_poly_fit_length(g, n);
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if (h->length == 0)
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_fmprb_vec_indeterminate(g->coeffs, n);
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else
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_fmprb_poly_rsqrt_series(g->coeffs, h->coeffs, h->length, n, prec);
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_fmprb_poly_set_length(g, n);
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_fmprb_poly_normalise(g);
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}
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