110 lines
3.2 KiB
C
110 lines
3.2 KiB
C
/* Compute complex natural logarithm.
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Copyright (C) 1997-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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, see
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<http://www.gnu.org/licenses/>. */
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#include "quadmath-imp.h"
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__complex128
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clogq (__complex128 x)
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{
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__complex128 result;
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int rcls = fpclassifyq (__real__ x);
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int icls = fpclassifyq (__imag__ x);
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if (__glibc_unlikely (rcls == QUADFP_ZERO && icls == QUADFP_ZERO))
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{
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/* Real and imaginary part are 0.0. */
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__imag__ result = signbitq (__real__ x) ? (__float128) M_PIq : 0;
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__imag__ result = copysignq (__imag__ result, __imag__ x);
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/* Yes, the following line raises an exception. */
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__real__ result = -1 / fabsq (__real__ x);
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}
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else if (__glibc_likely (rcls != QUADFP_NAN && icls != QUADFP_NAN))
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{
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/* Neither real nor imaginary part is NaN. */
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__float128 absx = fabsq (__real__ x), absy = fabsq (__imag__ x);
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int scale = 0;
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if (absx < absy)
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{
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__float128 t = absx;
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absx = absy;
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absy = t;
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}
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if (absx > FLT128_MAX / 2)
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{
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scale = -1;
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absx = scalbnq (absx, scale);
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absy = (absy >= FLT128_MIN * 2 ? scalbnq (absy, scale) : 0);
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}
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else if (absx < FLT128_MIN && absy < FLT128_MIN)
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{
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scale = FLT128_MANT_DIG;
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absx = scalbnq (absx, scale);
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absy = scalbnq (absy, scale);
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}
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if (absx == 1 && scale == 0)
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{
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__real__ result = log1pq (absy * absy) / 2;
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math_check_force_underflow_nonneg (__real__ result);
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}
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else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)
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{
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__float128 d2m1 = (absx - 1) * (absx + 1);
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if (absy >= FLT128_EPSILON)
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d2m1 += absy * absy;
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__real__ result = log1pq (d2m1) / 2;
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}
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else if (absx < 1
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&& absx >= 0.5Q
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&& absy < FLT128_EPSILON / 2
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&& scale == 0)
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{
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__float128 d2m1 = (absx - 1) * (absx + 1);
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__real__ result = log1pq (d2m1) / 2;
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}
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else if (absx < 1
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&& absx >= 0.5Q
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&& scale == 0
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&& absx * absx + absy * absy >= 0.5Q)
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{
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__float128 d2m1 = __quadmath_x2y2m1q (absx, absy);
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__real__ result = log1pq (d2m1) / 2;
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}
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else
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{
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__float128 d = hypotq (absx, absy);
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__real__ result = logq (d) - scale * (__float128) M_LN2q;
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}
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__imag__ result = atan2q (__imag__ x, __real__ x);
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}
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else
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{
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__imag__ result = nanq ("");
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if (rcls == QUADFP_INFINITE || icls == QUADFP_INFINITE)
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/* Real or imaginary part is infinite. */
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__real__ result = HUGE_VALQ;
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else
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__real__ result = nanq ("");
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}
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return result;
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}
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