summaryrefslogtreecommitdiff
path: root/src/math/acoshf.c
diff options
context:
space:
mode:
authorSzabolcs Nagy <nsz@port70.net>2013-09-05 12:26:26 +0000
committerSzabolcs Nagy <nsz@port70.net>2013-09-05 12:26:26 +0000
commit101e6012856918440b5d7474739c3fc22a8d3b85 (patch)
tree04b79d042e6dd3dda62afeecc9e9c80627616867 /src/math/acoshf.c
parent02343946215a7ae03634c6490abcc69da68df589 (diff)
downloadmusl-101e6012856918440b5d7474739c3fc22a8d3b85.tar.gz
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.c11
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;