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https://github.com/vale981/arb
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53 lines
1.7 KiB
C
53 lines
1.7 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) 2016 Pascal Molin
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******************************************************************************/
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#include "acb_dirichlet.h"
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#include <math.h>
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#define PI 3.14159265358
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#define LOG2 0.69314718055
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ulong
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acb_dirichlet_theta_length_d(ulong q, double t, slong prec)
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{
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double a, la;
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a = PI / (double)q * t * t;
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la = (a < .3) ? -log(2*a*(1-a)) : .8;
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la = ((double)prec * LOG2 + la) / a;
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return ceil(sqrt(la)+.5);
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}
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ulong
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acb_dirichlet_theta_length(ulong q, const arb_t t, slong prec)
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{
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double dt;
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ulong len;
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arf_t at;
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arf_init(at);
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arb_get_lbound_arf(at, t, 53);
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dt = arf_get_d(at, ARF_RND_DOWN);
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len = acb_dirichlet_theta_length_d(q, dt, prec);
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arf_clear(at);
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return len;
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}
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