mirror of
https://github.com/vale981/arb
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69 lines
2.2 KiB
C
69 lines
2.2 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_newton_refine_root(fmprb_t r, const fmprb_struct * poly, long len,
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const fmprb_t start,
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const fmprb_t convergence_interval,
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const fmpr_t convergence_factor,
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long eval_extra_prec,
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long prec)
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{
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long precs[FLINT_BITS];
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long i, iters, wp, padding, start_prec;
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start_prec = fmprb_rel_accuracy_bits(start);
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/* todo: padding should be based on the logarithm of convergence_factor */
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padding = 5;
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precs[0] = prec + padding;
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iters = 1;
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while ((iters < FLINT_BITS) && (precs[iters-1] + padding > 2*start_prec))
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{
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precs[iters] = (precs[iters-1] / 2) + padding;
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iters++;
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if (iters == FLINT_BITS)
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{
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printf("newton_refine_root: initial value too imprecise\n");
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abort();
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}
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}
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for (i = iters - 1; i >= 0; i--)
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{
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wp = precs[i] + eval_extra_prec;
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if (!_fmprb_poly_newton_step(r, poly, len, r, convergence_interval,
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convergence_factor, wp))
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{
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printf("warning: newton_refine_root: improvement failed\n");
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break;
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}
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}
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}
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