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| author | Damien George <damien.p.george@gmail.com> | 2017-06-23 15:52:00 +1000 |
|---|---|---|
| committer | Damien George <damien.p.george@gmail.com> | 2017-06-28 15:12:04 +1000 |
| commit | 045116551ec06d2619250cffff5e8b56a5f827d1 (patch) | |
| tree | 314e63ab9307cb0bc4d33486f173ced228209186 /lib/libm_dbl/asinh.c | |
| parent | 409fc8f9c1c5f07bcbdb6229196775deb4133e03 (diff) | |
| download | micropython-045116551ec06d2619250cffff5e8b56a5f827d1.tar.gz micropython-045116551ec06d2619250cffff5e8b56a5f827d1.zip | |
lib: Add libm_dbl, a double-precision math library, from musl-1.1.16.
Diffstat (limited to 'lib/libm_dbl/asinh.c')
| -rw-r--r-- | lib/libm_dbl/asinh.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/lib/libm_dbl/asinh.c b/lib/libm_dbl/asinh.c new file mode 100644 index 0000000000..0829f228ef --- /dev/null +++ b/lib/libm_dbl/asinh.c @@ -0,0 +1,28 @@ +#include "libm.h" + +/* asinh(x) = sign(x)*log(|x|+sqrt(x*x+1)) ~= x - x^3/6 + o(x^5) */ +double asinh(double x) +{ + union {double f; uint64_t i;} u = {.f = x}; + unsigned e = u.i >> 52 & 0x7ff; + unsigned s = u.i >> 63; + + /* |x| */ + u.i &= (uint64_t)-1/2; + x = u.f; + + if (e >= 0x3ff + 26) { + /* |x| >= 0x1p26 or inf or nan */ + x = log(x) + 0.693147180559945309417232121458176568; + } else if (e >= 0x3ff + 1) { + /* |x| >= 2 */ + x = log(2*x + 1/(sqrt(x*x+1)+x)); + } else if (e >= 0x3ff - 26) { + /* |x| >= 0x1p-26, up to 1.6ulp error in [0.125,0.5] */ + x = log1p(x + x*x/(sqrt(x*x+1)+1)); + } else { + /* |x| < 0x1p-26, raise inexact if x != 0 */ + FORCE_EVAL(x + 0x1p120f); + } + return s ? -x : x; +} |