From caf84319c1614d8aa867d8db80219f4e9b1bf735 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Tue, 30 Apr 2013 11:27:35 +0000 Subject: Fix catan, catanh inaccuracy from atan2 denominators near 0 (bug 15416). --- math/s_catanh.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) (limited to 'math/s_catanh.c') diff --git a/math/s_catanh.c b/math/s_catanh.c index 55c5628..5248cbc 100644 --- a/math/s_catanh.c +++ b/math/s_catanh.c @@ -89,7 +89,25 @@ __catanh (__complex__ double x) __real__ res = 0.25 * __log1p (num / den); } - den = 1 - __real__ x * __real__ x - i2; + double absx, absy; + + absx = fabs (__real__ x); + absy = fabs (__imag__ x); + if (absx < absy) + { + double t = absx; + absx = absy; + absy = t; + } + + if (absx >= 1.0) + den = (1.0 - absx) * (1.0 + absx) - absy * absy; + else if (absx >= 0.75 && absy < DBL_EPSILON / 2.0) + den = (1.0 - absx) * (1.0 + absx); + else if (absx >= 0.75 || absy >= 0.5) + den = -__x2y2m1 (absx, absy); + else + den = (1.0 - absx) * (1.0 + absx) - absy * absy; __imag__ res = 0.5 * __ieee754_atan2 (2.0 * __imag__ x, den); } -- cgit v1.1