108 lines
2.8 KiB
C
108 lines
2.8 KiB
C
/* Complex square root of float value.
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Copyright (C) 1997 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Based on an algorithm by Stephen L. Moshier <moshier@world.std.com>.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <complex.h>
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#include <math.h>
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#include "math_private.h"
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__complex__ float
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__csqrtf (__complex__ float x)
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{
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__complex__ float res;
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int rcls = fpclassify (__real__ x);
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int icls = fpclassify (__imag__ x);
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if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
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{
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if (icls == FP_INFINITE)
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{
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__real__ res = HUGE_VALF;
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__imag__ res = __imag__ x;
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}
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else if (rcls == FP_INFINITE)
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{
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if (__real__ x < 0.0)
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{
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__real__ res = icls == FP_NAN ? __nanf ("") : 0;
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__imag__ res = __copysignf (HUGE_VALF, __imag__ x);
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}
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else
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{
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__real__ res = __real__ x;
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__imag__ res = (icls == FP_NAN
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? __nanf ("") : __copysignf (0.0, __imag__ x));
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}
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}
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else
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{
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__real__ res = __nanf ("");
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__imag__ res = __nanf ("");
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}
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}
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else
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{
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if (icls == FP_ZERO)
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{
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if (__real__ x < 0.0)
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{
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__real__ res = 0.0;
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__imag__ res = __copysignf (__ieee754_sqrtf (-__real__ x),
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__imag__ x);
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}
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else
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{
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__real__ res = fabsf (__ieee754_sqrtf (__real__ x));
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__imag__ res = __copysignf (0.0, __imag__ x);
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}
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}
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else if (rcls == FP_ZERO)
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{
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float r = __ieee754_sqrtf (0.5 * fabsf (__imag__ x));
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__real__ res = __copysignf (r, __imag__ x);
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__imag__ res = r;
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}
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else
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{
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__complex__ float q;
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float t, r;
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if (fabsf (__imag__ x) < 2.0e-4 * fabsf (__real__ x))
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t = 0.25 * __imag__ x * (__imag__ x / __real__ x);
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else
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t = 0.5 * (__ieee754_hypotf (__real__ x, __imag__ x) - __real__ x);
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r = __ieee754_sqrtf (t);
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__real__ q = __imag__ x / (2.0 * r);
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__imag__ q = r;
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/* Heron iteration in complex arithmetic. */
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res = 0.5 * (q + q / x);
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}
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}
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return res;
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}
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weak_alias (__csqrtf, csqrtf)
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