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115 lines
2.9 KiB
C
115 lines
2.9 KiB
C
/* Complex square root of double value.
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Copyright (C) 1997, 1998 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 Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the 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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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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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__ double
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__csqrt (__complex__ double x)
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{
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__complex__ double 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_VAL;
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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 ? __nan ("") : 0;
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__imag__ res = __copysign (HUGE_VAL, __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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? __nan ("") : __copysign (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 = __nan ("");
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__imag__ res = __nan ("");
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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 = __copysign (__ieee754_sqrt (-__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 = fabs (__ieee754_sqrt (__real__ x));
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__imag__ res = __copysign (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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double r = __ieee754_sqrt (0.5 * fabs (__imag__ x));
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__real__ res = __copysign (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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double d, r, s;
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d = __ieee754_hypot (__real__ x, __imag__ x);
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/* Use the identity 2 Re res Im res = Im x
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to avoid cancellation error in d +/- Re x. */
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if (__real__ x > 0)
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{
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r = __ieee754_sqrt (0.5 * d + 0.5 * __real__ x);
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s = (0.5 * __imag__ x) / r;
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}
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else
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{
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s = __ieee754_sqrt (0.5 * d - 0.5 * __real__ x);
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r = fabs ((0.5 * __imag__ x) / s);
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}
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__real__ res = r;
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__imag__ res = __copysign (s, __imag__ 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 (__csqrt, csqrt)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__csqrt, __csqrtl)
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weak_alias (__csqrt, csqrtl)
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#endif
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