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| author | Szabolcs Nagy <nsz@port70.net> | 2013-09-05 12:26:26 +0000 |
|---|---|---|
| committer | Szabolcs Nagy <nsz@port70.net> | 2013-09-05 12:26:26 +0000 |
| commit | 101e6012856918440b5d7474739c3fc22a8d3b85 (patch) | |
| tree | 04b79d042e6dd3dda62afeecc9e9c80627616867 /src/math/acoshf.c | |
| parent | 02343946215a7ae03634c6490abcc69da68df589 (diff) | |
| download | musl-101e6012856918440b5d7474739c3fc22a8d3b85.tar.gz musl-101e6012856918440b5d7474739c3fc22a8d3b85.tar.xz musl-101e6012856918440b5d7474739c3fc22a8d3b85.zip | |
math: fix acoshf on negative values
acosh(x) is invalid for x<1, acoshf tried to be clever using signed comparisions to handle all x<2 the same way, but the formula was wrong on large negative values.
Diffstat (limited to 'src/math/acoshf.c')
| -rw-r--r-- | src/math/acoshf.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/src/math/acoshf.c b/src/math/acoshf.c index 4596085e..16550f19 100644 --- a/src/math/acoshf.c +++ b/src/math/acoshf.c @@ -3,14 +3,15 @@ /* acosh(x) = log(x + sqrt(x*x-1)) */ float acoshf(float x) { - union {float f; int32_t i;} u = {.f = x}; + union {float f; uint32_t i;} u = {x}; + uint32_t a = u.i & 0x7fffffff; - if (u.i < 0x3f800000+(1<<23)) - /* x < 2, invalid if x < 1 or nan */ + if (a < 0x3f800000+(1<<23)) + /* |x| < 2, invalid if x < 1 or nan */ /* up to 2ulp error in [1,1.125] */ return log1pf(x-1 + sqrtf((x-1)*(x-1)+2*(x-1))); - if (u.i < 0x3f800000+(12<<23)) - /* x < 0x1p12 */ + if (a < 0x3f800000+(12<<23)) + /* |x| < 0x1p12 */ return logf(2*x - 1/(x+sqrtf(x*x-1))); /* x >= 0x1p12 */ return logf(x) + 0.693147180559945309417232121458176568f; |