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authorJoseph Myers <joseph@codesourcery.com>2017-03-15 22:00:54 +0000
committerJoseph Myers <joseph@codesourcery.com>2017-03-15 22:00:54 +0000
commite4e52ff059f46472145433d2bd003d5383f89e82 (patch)
treec5044e3b2e2f98778087319e79d308bd817e9a75 /math/auto-libm-test-in
parent5d20a49aaccef5ef7adac93d5ca159f6b7ba0105 (diff)
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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 'math/auto-libm-test-in')
-rw-r--r--math/auto-libm-test-in4
1 files changed, 4 insertions, 0 deletions
diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in
index c8267aa822..6a47044f6b 100644
--- a/math/auto-libm-test-in
+++ b/math/auto-libm-test-in
@@ -4324,6 +4324,8 @@ cos -0x1.02e34cp+0
cos 0xf.f0274p+4
cos 0x3.042d88p+0
cos 0x1.8475e5afd4481p+0
+cos 1.57079697
+cos -1.57079697
cosh 0
cosh -0
@@ -7236,6 +7238,8 @@ tan 0x2.091d68p+0
tan -0x5.302ab9b18593264p+0
tan 0x1.1ad374p+0
tan -0x1.0d55b8p+0
+tan 1.57079697
+tan -1.57079697
tan 0x1p-5
tan 0x1p-10
tan 0x1p-15