mirror of
https://github.com/vale981/arb
synced 2025-03-06 01:41:39 -05:00
126 lines
3.5 KiB
C
126 lines
3.5 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_calc.h"
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/* TODO: refactor/combine some of this code with isolate_roots.c */
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/* 0 means that it *could* be zero; otherwise +/- 1 */
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static __inline__ int
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_fmprb_sign(const fmprb_t t)
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{
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if (fmprb_is_positive(t))
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return 1;
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else if (fmprb_is_negative(t))
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return -1;
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else
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return 0;
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}
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static int
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partition(fmprb_t L, fmprb_t R,
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fmprb_calc_func_t func, void * param, const fmprb_t block, long prec)
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{
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fmprb_t t, m;
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int msign;
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fmprb_init(t);
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fmprb_init(m);
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/* TODO: try other points */
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fmprb_set_fmpr(m, fmprb_midref(block));
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func(t, m, param, 1, prec);
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msign = _fmprb_sign(t);
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fmpr_mul_2exp_si(fmprb_radref(L), fmprb_radref(block), -1);
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fmpr_set(fmprb_radref(R), fmprb_radref(L));
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/* XXX: deal with huge shifts */
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fmpr_sub(fmprb_midref(L), fmprb_midref(block), fmprb_radref(L), FMPR_PREC_EXACT, FMPR_RND_DOWN);
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fmpr_add(fmprb_midref(R), fmprb_midref(block), fmprb_radref(R), FMPR_PREC_EXACT, FMPR_RND_DOWN);
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fmprb_clear(t);
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fmprb_clear(m);
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return msign;
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}
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int fmprb_calc_refine_root_bisect(fmprb_t r, fmprb_calc_func_t func,
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void * param, const fmprb_t start, long iter, long prec)
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{
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int asign, bsign, msign, result;
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long i;
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fmprb_t t, u;
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fmprb_init(t);
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fmprb_init(u);
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/* XXX: deal with huge shifts */
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fmpr_sub(fmprb_midref(t), fmprb_midref(start), fmprb_radref(start),
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FMPR_PREC_EXACT, FMPR_RND_DOWN);
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func(u, t, param, 1, prec);
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asign = _fmprb_sign(u);
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fmpr_add(fmprb_midref(t), fmprb_midref(start), fmprb_radref(start),
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FMPR_PREC_EXACT, FMPR_RND_DOWN);
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func(u, t, param, 1, prec);
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bsign = _fmprb_sign(u);
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/* must have proper sign changes */
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if (asign == 0 || bsign == 0 || asign == bsign)
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{
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result = FMPRB_CALC_IMPRECISE_INPUT;
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}
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else
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{
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fmprb_set(r, start);
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result = FMPRB_CALC_SUCCESS;
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for (i = 0; i < iter; i++)
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{
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msign = partition(t, u, func, param, r, prec);
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/* the algorithm fails if the value at the midpoint cannot
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be distinguished from zero */
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if (msign == 0)
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{
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result = FMPRB_CALC_NO_CONVERGENCE;
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break;
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}
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if (msign == asign)
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fmprb_swap(r, u);
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else
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fmprb_swap(r, t);
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}
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}
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fmprb_clear(t);
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fmprb_clear(u);
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return result;
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}
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