mirror of
https://github.com/vale981/arb
synced 2025-03-06 09:51:39 -05:00
99 lines
2.8 KiB
C
99 lines
2.8 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, 2013 Fredrik Johansson
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******************************************************************************/
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#include "fmprb.h"
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#define BINEXP_LIMIT 64
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void
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_fmprb_pow_exp(fmprb_t z, const fmprb_t x, int negx, const fmprb_t y, long prec)
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{
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fmprb_t t;
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fmprb_init(t);
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if (negx)
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{
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fmprb_neg(t, x);
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fmprb_log(t, t, prec);
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}
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else
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fmprb_log(t, x, prec);
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fmprb_mul(t, t, y, prec);
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fmprb_exp(z, t, prec);
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fmprb_clear(t);
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}
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void
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fmprb_pow(fmprb_t z, const fmprb_t x, const fmprb_t y, long prec)
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{
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const fmpr_struct * ymid = fmprb_midref(y);
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const fmpr_struct * yrad = fmprb_radref(y);
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if (fmprb_is_zero(y))
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{
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fmprb_one(z);
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return;
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}
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if (fmpr_is_zero(yrad) && !fmpr_is_special(fmprb_midref(x)))
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{
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/* small half-integer or integer */
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if (fmpr_cmpabs_2exp_si(ymid, BINEXP_LIMIT) < 0 &&
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fmpr_is_int_2exp_si(ymid, -1))
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{
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fmpz_t e;
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fmpz_init(e);
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if (fmpr_is_int(ymid))
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{
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fmpr_get_fmpz_fixed_si(e, ymid, 0);
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fmprb_pow_fmpz_binexp(z, x, e, prec);
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}
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else
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{
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fmpr_get_fmpz_fixed_si(e, ymid, -1);
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fmprb_sqrt(z, x, prec + fmpz_bits(e));
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fmprb_pow_fmpz_binexp(z, z, e, prec);
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}
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fmpz_clear(e);
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return;
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}
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else if (fmpr_is_int(ymid) && fmpr_sgn(fmprb_midref(x)) < 0)
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{
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/* use (-x)^n = (-1)^n * x^n to avoid NaNs
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at least at high enough precision */
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int odd = !fmpr_is_int_2exp_si(ymid, 1);
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_fmprb_pow_exp(z, x, 1, y, prec);
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if (odd)
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fmprb_neg(z, z);
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return;
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}
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}
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_fmprb_pow_exp(z, x, 0, y, prec);
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}
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