diff options
Diffstat (limited to 'src/math/atanh.c')
| -rw-r--r-- | src/math/atanh.c | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/src/math/atanh.c b/src/math/atanh.c index 84a84c69..63a035d7 100644 --- a/src/math/atanh.c +++ b/src/math/atanh.c @@ -6,16 +6,24 @@ double atanh(double x) union {double f; uint64_t i;} u = {.f = x}; unsigned e = u.i >> 52 & 0x7ff; unsigned s = u.i >> 63; + double_t y; /* |x| */ u.i &= (uint64_t)-1/2; - x = u.f; + y = u.f; if (e < 0x3ff - 1) { - /* |x| < 0.5, up to 1.7ulp error */ - x = 0.5*log1p(2*x + 2*x*x/(1-x)); + if (e < 0x3ff - 32) { + /* handle underflow */ + if (e == 0) + FORCE_EVAL((float)y); + } else { + /* |x| < 0.5, up to 1.7ulp error */ + y = 0.5*log1p(2*y + 2*y*y/(1-y)); + } } else { - x = 0.5*log1p(2*x/(1-x)); + /* avoid overflow */ + y = 0.5*log1p(2*(y/(1-y))); } - return s ? -x : x; + return s ? -y : y; } |