mirror of
https://github.com/vale981/arb
synced 2025-03-05 09:21:38 -05:00
88 lines
2.1 KiB
C
88 lines
2.1 KiB
C
/*
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Copyright (C) 2017 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 "acb_hypgeom.h"
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#include "bernoulli.h"
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static void
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_arf_trunc(arf_t x)
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{
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if (arf_sgn(x) < 0)
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arf_ceil(x, x);
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else
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arf_floor(x, x);
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}
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static void
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acb_extract_bits(acb_t t, const acb_t z, slong b)
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{
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acb_mul_2exp_si(t, z, b);
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_arf_trunc(arb_midref(acb_realref(t)));
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_arf_trunc(arb_midref(acb_imagref(t)));
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mag_zero(arb_radref(acb_realref(t)));
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mag_zero(arb_radref(acb_imagref(t)));
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acb_mul_2exp_si(t, t, -b);
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}
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void
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acb_hypgeom_dilog_bitburst(acb_t res, acb_t z0, const acb_t z, slong prec)
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{
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acb_t s, t, tprev, u;
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slong w;
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slong start = 16;
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acb_init(s);
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acb_init(t);
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acb_init(tprev);
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acb_init(u);
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acb_sub_ui(t, z, 1, 30);
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arb_abs(acb_imagref(t), acb_imagref(t));
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/* we don't want to end up on the branch cut */
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if (arb_contains_nonnegative(acb_realref(t))
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&& !arb_gt(acb_imagref(t), acb_realref(t)))
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{
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acb_set(z0, z);
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acb_zero(res);
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}
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else
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{
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acb_extract_bits(t, z, start);
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acb_set(z0, t);
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acb_set(tprev, t);
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for (w = 2 * start; w < prec; w *= 2)
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{
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acb_extract_bits(t, z, w);
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acb_sub(u, t, z, 30);
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if (arf_cmpabs_2exp_si(arb_midref(acb_realref(u)), -prec / 8) < 0 &&
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arf_cmpabs_2exp_si(arb_midref(acb_realref(u)), -prec / 8) < 0)
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break;
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acb_hypgeom_dilog_continuation(u, tprev, t, prec);
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acb_add(s, s, u, prec);
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acb_set(tprev, t);
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}
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acb_hypgeom_dilog_continuation(u, tprev, z, prec);
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acb_add(s, s, u, prec);
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acb_set(res, s);
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}
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acb_clear(s);
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acb_clear(t);
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acb_clear(tprev);
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acb_clear(u);
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}
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