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0244fe0e46
When rounding up, the error bound sometimes came out as 1/2 ulp instead of 1 ulp due to the mantissa rounding up to the next power of two, without a corresponding exponent correction. Fortunately, this should not affect ball arithmetic (which always rounds down).
92 lines
2.6 KiB
C
92 lines
2.6 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) 2012 Fredrik Johansson
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******************************************************************************/
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#include "fmpr.h"
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long
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_fmpr_normalise_naive(fmpz_t man, fmpz_t exp, long prec, fmpr_rnd_t rnd)
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{
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/* TODO: this should perhaps raise an exception to avoid ambiguity */
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if (fmpz_is_zero(man))
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{
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fmpz_zero(exp);
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return FMPR_RESULT_EXACT;
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}
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else
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{
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long bc, val;
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bc = fmpz_bits(man);
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val = fmpz_val2(man);
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if (bc - val <= prec)
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{
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if (val != 0)
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{
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fmpz_tdiv_q_2exp(man, man, val);
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fmpz_add_ui(exp, exp, val);
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}
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return FMPR_RESULT_EXACT;
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}
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else
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{
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long exp_shift = bc - prec;
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if (rnd == FMPR_RND_NEAR)
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{
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abort();
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}
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else if (rnd == FMPR_RND_DOWN)
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{
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fmpz_tdiv_q_2exp(man, man, exp_shift);
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}
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else if (rnd == FMPR_RND_FLOOR)
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{
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fmpz_fdiv_q_2exp(man, man, exp_shift);
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}
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else if (rnd == FMPR_RND_CEIL)
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{
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fmpz_cdiv_q_2exp(man, man, exp_shift);
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}
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else
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{
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if (fmpz_sgn(man) > 0)
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fmpz_cdiv_q_2exp(man, man, exp_shift);
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else
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fmpz_fdiv_q_2exp(man, man, exp_shift);
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}
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val = fmpz_val2(man);
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exp_shift += val;
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if (val != 0)
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fmpz_tdiv_q_2exp(man, man, val);
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fmpz_add_ui(exp, exp, exp_shift);
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return val - (val == prec);
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}
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}
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}
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