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author | Joseph Myers <joseph@codesourcery.com> | 2017-03-15 22:00:54 +0000 |
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committer | Joseph Myers <joseph@codesourcery.com> | 2017-03-15 22:00:54 +0000 |
commit | e4e52ff059f46472145433d2bd003d5383f89e82 (patch) | |
tree | c5044e3b2e2f98778087319e79d308bd817e9a75 /ChangeLog | |
parent | 5d20a49aaccef5ef7adac93d5ca159f6b7ba0105 (diff) | |
download | glibc-e4e52ff059f46472145433d2bd003d5383f89e82.tar.gz glibc-e4e52ff059f46472145433d2bd003d5383f89e82.tar.xz glibc-e4e52ff059f46472145433d2bd003d5383f89e82.zip |
Improve float range reduction accuracy near pi/2 (bug 21094).
Bug 21094 reports 3ulp errors of cosf and tanf for certain arguments near pi/2 arising from the use of an insufficiently accurate range reduction. (To be clear, this is a quality-of-implementation issue relating to the apparent intent of those particular cosf and tanf implementations; 3ulp is within the general glibc accuracy goals, so not inherently a bug.) This patch fixes that error by making a wider range of cases use the existing more accurate range reduction for arguments close to pi/2. The wider range of values is still narrow enough for the "z -= pio2_2;" in the more accurate case to be exact, as the code expects. Tested for x86_64, x86 and mips64; no ulps updates needed (but at least on mips64, the larger ulps were seen if the tests were added without the substantive fix). [BZ #21094] * sysdeps/ieee754/flt-32/e_rem_pio2f.c (__ieee754_rem_pio2f): Use 24+24+24-bit pi for wider range of values around pi/2. * math/auto-libm-test-in: Add more tests of cos and tan. * math/auto-libm-test-out-cos: Regenerated. * math/auto-libm-test-out-tan: Likewise.
Diffstat (limited to 'ChangeLog')
-rw-r--r-- | ChangeLog | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog index f8b2e60bd6..f1f9ceb7ec 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,12 @@ +2017-03-15 Joseph Myers <joseph@codesourcery.com> + + [BZ #21094] + * sysdeps/ieee754/flt-32/e_rem_pio2f.c (__ieee754_rem_pio2f): Use + 24+24+24-bit pi for wider range of values around pi/2. + * math/auto-libm-test-in: Add more tests of cos and tan. + * math/auto-libm-test-out-cos: Regenerated. + * math/auto-libm-test-out-tan: Likewise. + 2017-03-15 John David Anglin <danglin@gcc.gnu.org> * sysdeps/hppa/dl-machine.h (DL_STACK_END): Define. |