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glibc/math/k_casinh.c
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/* Return arc hyperbole sine for double value, with the imaginary part | |
of the result possibly adjusted for use in computing other | |
functions. | |
Copyright (C) 1997-2016 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <complex.h> | |
#include <math.h> | |
#include <math_private.h> | |
#include <float.h> | |
/* Return the complex inverse hyperbolic sine of finite nonzero Z, | |
with the imaginary part of the result subtracted from pi/2 if ADJ | |
is nonzero. */ | |
__complex__ double | |
__kernel_casinh (__complex__ double x, int adj) | |
{ | |
__complex__ double res; | |
double rx, ix; | |
__complex__ double y; | |
/* Avoid cancellation by reducing to the first quadrant. */ | |
rx = fabs (__real__ x); | |
ix = fabs (__imag__ x); | |
if (rx >= 1.0 / DBL_EPSILON || ix >= 1.0 / DBL_EPSILON) | |
{ | |
/* For large x in the first quadrant, x + csqrt (1 + x * x) | |
is sufficiently close to 2 * x to make no significant | |
difference to the result; avoid possible overflow from | |
the squaring and addition. */ | |
__real__ y = rx; | |
__imag__ y = ix; | |
if (adj) | |
{ | |
double t = __real__ y; | |
__real__ y = __copysign (__imag__ y, __imag__ x); | |
__imag__ y = t; | |
} | |
res = __clog (y); | |
__real__ res += M_LN2; | |
} | |
else if (rx >= 0.5 && ix < DBL_EPSILON / 8.0) | |
{ | |
double s = __ieee754_hypot (1.0, rx); | |
__real__ res = __ieee754_log (rx + s); | |
if (adj) | |
__imag__ res = __ieee754_atan2 (s, __imag__ x); | |
else | |
__imag__ res = __ieee754_atan2 (ix, s); | |
} | |
else if (rx < DBL_EPSILON / 8.0 && ix >= 1.5) | |
{ | |
double s = __ieee754_sqrt ((ix + 1.0) * (ix - 1.0)); | |
__real__ res = __ieee754_log (ix + s); | |
if (adj) | |
__imag__ res = __ieee754_atan2 (rx, __copysign (s, __imag__ x)); | |
else | |
__imag__ res = __ieee754_atan2 (s, rx); | |
} | |
else if (ix > 1.0 && ix < 1.5 && rx < 0.5) | |
{ | |
if (rx < DBL_EPSILON * DBL_EPSILON) | |
{ | |
double ix2m1 = (ix + 1.0) * (ix - 1.0); | |
double s = __ieee754_sqrt (ix2m1); | |
__real__ res = __log1p (2.0 * (ix2m1 + ix * s)) / 2.0; | |
if (adj) | |
__imag__ res = __ieee754_atan2 (rx, __copysign (s, __imag__ x)); | |
else | |
__imag__ res = __ieee754_atan2 (s, rx); | |
} | |
else | |
{ | |
double ix2m1 = (ix + 1.0) * (ix - 1.0); | |
double rx2 = rx * rx; | |
double f = rx2 * (2.0 + rx2 + 2.0 * ix * ix); | |
double d = __ieee754_sqrt (ix2m1 * ix2m1 + f); | |
double dp = d + ix2m1; | |
double dm = f / dp; | |
double r1 = __ieee754_sqrt ((dm + rx2) / 2.0); | |
double r2 = rx * ix / r1; | |
__real__ res = __log1p (rx2 + dp + 2.0 * (rx * r1 + ix * r2)) / 2.0; | |
if (adj) | |
__imag__ res = __ieee754_atan2 (rx + r1, __copysign (ix + r2, | |
__imag__ x)); | |
else | |
__imag__ res = __ieee754_atan2 (ix + r2, rx + r1); | |
} | |
} | |
else if (ix == 1.0 && rx < 0.5) | |
{ | |
if (rx < DBL_EPSILON / 8.0) | |
{ | |
__real__ res = __log1p (2.0 * (rx + __ieee754_sqrt (rx))) / 2.0; | |
if (adj) | |
__imag__ res = __ieee754_atan2 (__ieee754_sqrt (rx), | |
__copysign (1.0, __imag__ x)); | |
else | |
__imag__ res = __ieee754_atan2 (1.0, __ieee754_sqrt (rx)); | |
} | |
else | |
{ | |
double d = rx * __ieee754_sqrt (4.0 + rx * rx); | |
double s1 = __ieee754_sqrt ((d + rx * rx) / 2.0); | |
double s2 = __ieee754_sqrt ((d - rx * rx) / 2.0); | |
__real__ res = __log1p (rx * rx + d + 2.0 * (rx * s1 + s2)) / 2.0; | |
if (adj) | |
__imag__ res = __ieee754_atan2 (rx + s1, __copysign (1.0 + s2, | |
__imag__ x)); | |
else | |
__imag__ res = __ieee754_atan2 (1.0 + s2, rx + s1); | |
} | |
} | |
else if (ix < 1.0 && rx < 0.5) | |
{ | |
if (ix >= DBL_EPSILON) | |
{ | |
if (rx < DBL_EPSILON * DBL_EPSILON) | |
{ | |
double onemix2 = (1.0 + ix) * (1.0 - ix); | |
double s = __ieee754_sqrt (onemix2); | |
__real__ res = __log1p (2.0 * rx / s) / 2.0; | |
if (adj) | |
__imag__ res = __ieee754_atan2 (s, __imag__ x); | |
else | |
__imag__ res = __ieee754_atan2 (ix, s); | |
} | |
else | |
{ | |
double onemix2 = (1.0 + ix) * (1.0 - ix); | |
double rx2 = rx * rx; | |
double f = rx2 * (2.0 + rx2 + 2.0 * ix * ix); | |
double d = __ieee754_sqrt (onemix2 * onemix2 + f); | |
double dp = d + onemix2; | |
double dm = f / dp; | |
double r1 = __ieee754_sqrt ((dp + rx2) / 2.0); | |
double r2 = rx * ix / r1; | |
__real__ res | |
= __log1p (rx2 + dm + 2.0 * (rx * r1 + ix * r2)) / 2.0; | |
if (adj) | |
__imag__ res = __ieee754_atan2 (rx + r1, | |
__copysign (ix + r2, | |
__imag__ x)); | |
else | |
__imag__ res = __ieee754_atan2 (ix + r2, rx + r1); | |
} | |
} | |
else | |
{ | |
double s = __ieee754_hypot (1.0, rx); | |
__real__ res = __log1p (2.0 * rx * (rx + s)) / 2.0; | |
if (adj) | |
__imag__ res = __ieee754_atan2 (s, __imag__ x); | |
else | |
__imag__ res = __ieee754_atan2 (ix, s); | |
} | |
math_check_force_underflow_nonneg (__real__ res); | |
} | |
else | |
{ | |
__real__ y = (rx - ix) * (rx + ix) + 1.0; | |
__imag__ y = 2.0 * rx * ix; | |
y = __csqrt (y); | |
__real__ y += rx; | |
__imag__ y += ix; | |
if (adj) | |
{ | |
double t = __real__ y; | |
__real__ y = __copysign (__imag__ y, __imag__ x); | |
__imag__ y = t; | |
} | |
res = __clog (y); | |
} | |
/* Give results the correct sign for the original argument. */ | |
__real__ res = __copysign (__real__ res, __real__ x); | |
__imag__ res = __copysign (__imag__ res, (adj ? 1.0 : __imag__ x)); | |
return res; | |
} |