mirror of
https://github.com/vale981/arb
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71 lines
1.5 KiB
C
71 lines
1.5 KiB
C
/*
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Copyright (C) 2016 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_dirichlet.h"
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void
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acb_dirichlet_zeta_rs_d_coeffs(arb_ptr d, const arb_t sigma, slong k, slong prec)
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{
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slong j, r, m;
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arb_t u;
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arb_init(u);
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arb_one(u);
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arb_submul_ui(u, sigma, 2, prec);
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if (k == 0)
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{
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arb_one(d);
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arb_zero(d + 1);
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return;
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}
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for (j = (3 * k) / 2; j >= 0; j--)
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{
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m = 3 * k - 2 * j;
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if (m != 0)
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{
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arb_mul_2exp_si(d + j, d + j, -1);
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if (j >= 1)
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arb_addmul(d + j, d + j - 1, u, prec);
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arb_div_ui(d + j, d + j, 2 * m, prec);
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if (j >= 2)
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arb_submul_ui(d + j, d + j - 2, m + 1, prec);
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}
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}
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if (k % 2 == 0)
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{
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j = (3 * k) / 2;
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arb_zero(d + j);
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arb_set_ui(u, 2);
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for (r = j - 1; r >= 0; r--)
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{
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if ((j - r) % 2 == 0)
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arb_submul(d + j, d + r, u, prec);
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else
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arb_addmul(d + j, d + r, u, prec);
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arb_mul_ui(u, u, 4 * j - 4 * r + 2, prec);
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}
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}
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arb_zero(d + (3 * k) / 2 + 1);
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arb_clear(u);
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}
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