mirror of
https://github.com/vale981/arb
synced 2025-03-06 18:01:39 -05:00
99 lines
3.1 KiB
C
99 lines
3.1 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 "elefun.h"
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int
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elefun_exp_precomp(fmprb_t z, const fmprb_t x, long prec, int minus_one)
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{
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fmpz_t zfixed, zfixed_err, exponent, xfixed, xfixed_err;
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fmpr_t terr;
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long mag, fixed_wp;
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/* require radius < 0.25 */
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if (fmpr_cmp_2exp_si(fmprb_radref(x), -2) >= 0)
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return 0;
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if (fmpr_cmpabs_2exp_si(fmprb_midref(x), 128) >= 0)
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return 0;
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if (fmpr_cmpabs_2exp_si(fmprb_midref(x), -prec) < 0)
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return 0;
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fixed_wp = prec + 2 * FLINT_BIT_COUNT(prec);
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mag = *fmpr_expref(fmprb_midref(x)) + fmpz_bits(fmpr_manref(fmprb_midref(x)));
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if (mag > 0)
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fixed_wp += mag; /* for argument reduction */
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else if (minus_one)
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fixed_wp += -mag; /* cancellation */
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if (fixed_wp > EXP_CACHE_PREC)
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return 0;
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fmpz_init(zfixed);
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fmpz_init(zfixed_err);
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fmpz_init(exponent);
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fmpz_init(xfixed);
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fmpz_init(xfixed_err);
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fmpr_init(terr);
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fmpr_get_fmpz_fixed_si(xfixed, fmprb_midref(x), -fixed_wp);
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/* convert radius to fixed-point number; need to add 1 for
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error rounding midpoint, 1 for rounding the error itself */
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fmpr_get_fmpz_fixed_si(xfixed_err, fmprb_radref(x), -fixed_wp);
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fmpz_add_ui(xfixed_err, xfixed_err, 2);
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/* compute exp(x) as a fixed-point number */
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elefun_exp_fixed_precomp(zfixed, zfixed_err, exponent, xfixed, xfixed_err, fixed_wp);
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fmpz_sub_ui(exponent, exponent, fixed_wp);
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/* convert back to floating-point interval */
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if (minus_one)
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{
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fmprb_set_fmpz_2exp(z, zfixed, exponent);
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fmprb_sub_ui(z, z, 1, prec);
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}
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else
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{
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fmprb_set_round_fmpz_2exp(z, zfixed, exponent, prec);
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}
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/* add error */
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fmpr_set_round_fmpz_2exp(terr, zfixed_err, exponent, FMPRB_RAD_PREC, FMPR_RND_UP);
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fmpr_add(fmprb_radref(z), fmprb_radref(z), terr, FMPRB_RAD_PREC, FMPR_RND_UP);
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fmpz_clear(zfixed);
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fmpz_clear(zfixed_err);
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fmpz_clear(exponent);
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fmpz_clear(xfixed);
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fmpz_clear(xfixed_err);
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fmpr_clear(terr);
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return 1;
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}
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