mirror of
https://github.com/vale981/arb
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78 lines
2.3 KiB
C
78 lines
2.3 KiB
C
/*
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Copyright (C) 2014 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 "arf.h"
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/* Top-aligns the single-limb integer value v and rounds it to prec bits.
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Writes inexact, v, exp. Warning: macro without parentheses. */
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#define ARF_NORMALISE_ROUND_LIMB(inexact, exp, v, sgnbit, prec, rnd) \
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do { \
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count_leading_zeros(exp, v); \
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v <<= exp; \
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exp = FLINT_BITS - exp; \
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if (prec >= exp) \
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{ \
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inexact = 0; \
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} \
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else \
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{ \
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mp_limb_t hi_mask, lo_mask, rndn_mask, __t, __u; \
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hi_mask = LIMB_ONES << (FLINT_BITS - prec); \
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__t = v & hi_mask; \
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inexact = (__t != v); \
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if (inexact && rnd != ARF_RND_DOWN) \
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{ \
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if (rnd == ARF_RND_NEAR) \
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{ \
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lo_mask = LIMB_ONES >> prec; \
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rndn_mask = LIMB_ONE << (FLINT_BITS - prec - 1); \
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__u = v & lo_mask; \
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if (__u > rndn_mask || (__u == rndn_mask && \
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(__t << (prec - 1)))) \
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__t += (LIMB_ONE << (FLINT_BITS - prec)); \
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} \
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else if (arf_rounds_up(rnd, sgnbit)) \
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{ \
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__t += (LIMB_ONE << (FLINT_BITS - prec)); \
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} \
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if (__t == 0) \
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{ \
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__t = LIMB_TOP; \
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exp++; \
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} \
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} \
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v = __t; \
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} \
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} while (0)
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int
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_arf_set_round_ui(arf_t x, ulong v, int sgnbit, slong prec, arf_rnd_t rnd)
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{
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_fmpz_demote(ARF_EXPREF(x));
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ARF_DEMOTE(x);
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if (v == 0)
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{
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ARF_EXP(x) = ARF_EXP_ZERO;
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ARF_XSIZE(x) = 0;
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return 0;
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}
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else
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{
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int exp, inexact;
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ARF_NORMALISE_ROUND_LIMB(inexact, exp, v, sgnbit, prec, rnd);
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ARF_EXP(x) = exp;
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ARF_XSIZE(x) = ARF_MAKE_XSIZE(1, sgnbit);
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ARF_NOPTR_D(x)[0] = v;
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return inexact;
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}
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}
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