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| author | Joseph Myers <joseph@codesourcery.com> | 2015-05-15 17:21:08 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-05-15 17:21:08 +0000 |
| commit | ff069f024ae8cf15d53429e034d67ddcece0f67a (patch) | |
| tree | d6ad47bf62f47e532cadb862d427eaa2f610c12c /ChangeLog | |
| parent | b2fb25240813266e4f62f2dd039573f1a042ea2f (diff) | |
| download | glibc-ff069f024ae8cf15d53429e034d67ddcece0f67a.zip glibc-ff069f024ae8cf15d53429e034d67ddcece0f67a.tar.gz glibc-ff069f024ae8cf15d53429e034d67ddcece0f67a.tar.bz2 | |
Fix lgammaf spurious underflows (bug 18220).
The flt-32 implementation of lgammaf produces spurious underflow
exceptions for some large arguments, because of calculations involving
x^-2 multiplied by small constants. This patch fixes this by
adjusting the threshold for a simpler computation to 2**26 (the error
in the simpler computation is on the order of 0.5 * log (x), for a
result on the order of x * log (x)).
Tested for x86_64 and x86.
[BZ #18220]
* sysdeps/ieee754/flt-32/e_lgammaf_r.c (__ieee754_lgammaf_r): Use
2**26 not 2**58 as threshold for returning x * (log (x) - 1).
* math/auto-libm-test-in: Add another test of lgamma.
* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'ChangeLog')
| -rw-r--r-- | ChangeLog | 8 |
1 files changed, 8 insertions, 0 deletions
@@ -1,3 +1,11 @@ +2015-05-15 Joseph Myers <joseph@codesourcery.com> + + [BZ #18220] + * sysdeps/ieee754/flt-32/e_lgammaf_r.c (__ieee754_lgammaf_r): Use + 2**26 not 2**58 as threshold for returning x * (log (x) - 1). + * math/auto-libm-test-in: Add another test of lgamma. + * math/auto-libm-test-out: Regenerated. + 2015-05-15 Wilco Dijkstra <wdijkstr@arm.com> * stdio-common/printf_fp.c (___printf_fp): Use abs. |