mirror of
https://github.com/vale981/arb
synced 2025-03-04 17:01:40 -05:00
83 lines
1.7 KiB
C
83 lines
1.7 KiB
C
/*
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Copyright (C) 2021 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 "arb_hypgeom.h"
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int
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_arf_increment_fast(arf_t x, slong prec)
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{
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if (arf_sgn(x) > 0)
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{
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mp_limb_t hi, v, cy;
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mp_ptr xptr;
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mp_size_t xn;
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slong xexp;
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xexp = ARF_EXP(x);
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if (xexp >= 1 && xexp <= FLINT_BITS - 1)
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{
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ARF_GET_MPN_READONLY(xptr, xn, x);
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hi = xptr[xn - 1];
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v = hi + (UWORD(1) << (FLINT_BITS - xexp));
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cy = v < hi;
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if (cy == 0)
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{
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xptr[xn - 1] = v;
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return 0;
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}
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}
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}
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return arf_add_ui(x, x, 1, prec, ARF_RND_DOWN);
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}
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void
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_arb_increment_fast(arb_t x, slong prec)
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{
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if (_arf_increment_fast(arb_midref(x), prec))
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arf_mag_add_ulp(arb_radref(x), arb_radref(x), arb_midref(x), prec);
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}
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void
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arb_hypgeom_rising_ui_forward(arb_t res, const arb_t x, ulong n, slong prec)
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{
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arb_t t;
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ulong k;
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slong wp;
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if (n <= 1)
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{
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if (n == 0)
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arb_one(res);
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else
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arb_set_round(res, x, prec);
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return;
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}
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wp = prec + FLINT_BIT_COUNT(n);
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arb_init(t);
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arb_add_ui(t, x, 1, wp);
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arb_mul(res, x, t, (n == 2) ? prec : wp);
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for (k = 2; k < n; k++)
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{
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_arb_increment_fast(t, wp);
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arb_mul(res, res, t, k == (n - 1) ? prec : wp);
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}
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arb_clear(t);
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}
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