mirror of
https://github.com/vale981/arb
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94 lines
2.3 KiB
C
94 lines
2.3 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 "gamma.h"
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/* assumes y and x are not aliased */
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static void
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bsplit(fmprb_t y, const fmprb_t x, ulong a, ulong b, long prec)
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{
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if (b - a == 1)
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{
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fmprb_set_round(y, x, prec);
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}
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else if (b - a <= 10)
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{
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long i;
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fmprb_t t;
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fmprb_init(t);
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fmprb_add_ui(t, x, a, prec);
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fmprb_add_ui(y, x, a + 1, prec);
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fmprb_mul(y, y, t, prec);
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for (i = a + 2; i < b; i++)
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{
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fmprb_add_ui(t, x, i, prec);
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fmprb_mul(y, y, t, prec);
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}
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fmprb_clear(t);
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}
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else
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{
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fmprb_t t, u;
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ulong m = a + (b - a) / 2;
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fmprb_init(t);
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fmprb_init(u);
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bsplit(t, x, a, m, prec);
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bsplit(u, x, m, b, prec);
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fmprb_mul(y, t, u, prec);
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fmprb_clear(t);
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fmprb_clear(u);
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}
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}
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void
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gamma_rising_fmprb_ui_bsplit_simple(fmprb_t y, const fmprb_t x, ulong n, long prec)
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{
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if (n == 0)
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{
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fmprb_one(y);
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}
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else if (n == 1)
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{
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fmprb_set_round(y, x, prec);
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}
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else
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{
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fmprb_t t;
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long wp = FMPR_PREC_ADD(prec, FLINT_BIT_COUNT(n));
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fmprb_init(t);
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bsplit(t, x, 0, n, wp);
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fmprb_set_round(y, t, prec);
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fmprb_clear(t);
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}
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}
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