mirror of
https://github.com/vale981/arb
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71 lines
2 KiB
C
71 lines
2 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) 2014 Fredrik Johansson
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******************************************************************************/
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#include "mag.h"
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void
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mag_rsqrt(mag_t y, const mag_t x)
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{
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if (mag_is_special(x))
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{
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if (mag_is_zero(x))
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mag_inf(y);
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else
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mag_zero(y);
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}
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else
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{
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double t;
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fmpz e;
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t = MAG_MAN(x) * ldexp(1.0, -MAG_BITS);
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e = MAG_EXP(x);
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if (!COEFF_IS_MPZ(e))
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{
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if (e % 2 != 0)
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{
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e = (1 - e) >> 1;
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t *= 2.0;
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}
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else
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{
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e = (-e) >> 1;
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}
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t = (1.0 / sqrt(t)) * (1 + 1e-13);
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mag_set_d_2exp_fmpz(y, t, &e);
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}
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else
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{
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if (fmpz_is_odd(MAG_EXPREF(x)))
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t *= 2.0;
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fmpz_fdiv_q_2exp(MAG_EXPREF(y), MAG_EXPREF(x), 1);
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fmpz_neg(MAG_EXPREF(y), MAG_EXPREF(y));
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t = (1.0 / sqrt(t)) * (1 + 1e-13);
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mag_set_d_2exp_fmpz(y, t, MAG_EXPREF(y));
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}
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}
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}
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