mirror of
https://github.com/vale981/arb
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93 lines
2.5 KiB
C
93 lines
2.5 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) 2014 Fredrik Johansson
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******************************************************************************/
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#include "acb_poly.h"
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static ulong choose_M(ulong N, long target)
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{
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return FLINT_MIN(N, target + N / 100);
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}
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void
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_acb_poly_zeta_em_choose_param(arf_t bound, ulong * N, ulong * M, const acb_t s, const acb_t a, long d, long target, long prec)
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{
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ulong A, B, C;
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arf_t Abound, Bbound, Cbound, tol;
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arf_init(Abound);
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arf_init(Bbound);
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arf_init(Cbound);
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arf_init(tol);
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arf_set_si_2exp_si(tol, 1, -target);
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A = 1;
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B = 2;
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_acb_poly_zeta_em_bound1(Bbound, s, a, B, choose_M(B, target), d, prec);
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if (arf_cmp(Bbound, tol) > 0)
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{
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while (arf_cmp(Bbound, tol) > 0)
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{
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arf_set(Abound, Bbound);
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A *= 2;
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B *= 2;
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if (B == 0) abort();
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_acb_poly_zeta_em_bound1(Bbound, s, a, B, choose_M(B, target), d, prec);
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}
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/* bisect (-A, B] */
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while (B > A + 4)
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{
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C = A + (B - A) / 2;
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_acb_poly_zeta_em_bound1(Cbound, s, a, C, choose_M(C, target), d, prec);
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if (arf_cmp(Cbound, tol) < 0)
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{
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B = C;
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arf_set(Bbound, Cbound);
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}
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else
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{
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A = C;
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arf_set(Abound, Cbound);
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}
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}
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}
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arf_set(bound, Bbound);
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*N = B;
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*M = choose_M(B, target);
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arf_clear(Abound);
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arf_clear(Bbound);
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arf_clear(Cbound);
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arf_clear(tol);
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}
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