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| author | Joseph Myers <joseph@codesourcery.com> | 2015-02-25 00:01:15 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-02-25 00:01:15 +0000 |
| commit | 440169d681cc9f422e8486f1324079bef0e0c35a (patch) | |
| tree | 9b732f618ba081518cf0cca84ef33328526a4633 /sysdeps/ieee754 | |
| parent | ba7d2c543f7d69883ece7eab39bf6c5cd5dc3081 (diff) | |
| download | glibc-440169d681cc9f422e8486f1324079bef0e0c35a.zip glibc-440169d681cc9f422e8486f1324079bef0e0c35a.tar.gz glibc-440169d681cc9f422e8486f1324079bef0e0c35a.tar.bz2 | |
Fix ldbl-128ibm acoshl inaccuracy (bug 18019).
The ldbl-128ibm implementation of acoshl uses a cut-off of 0x1p28 to
determine when to use log(x) + log(2) as a formula. That cut-off is
too small for this format, resulting in large errors. This patch
changes it to a more appropriate cut-off of 0x1p56, adding tests
around the cut-offs for various floating-point formats.
Tested for powerpc. Also tested for x86_64 and x86 and updated ulps.
[BZ #18019]
* sysdeps/ieee754/ldbl-128ibm/e_acoshl.c (__ieee754_acoshl): Use
2**56 not 2**28 as threshold for log (2x) formula.
* math/auto-libm-test-in: Add more tests of acosh.
* math/auto-libm-test-out: Regenerated.
* sysdeps/i386/fpu/libm-test-ulps: Update.
* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
Diffstat (limited to 'sysdeps/ieee754')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/e_acoshl.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c b/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c index b0b33f7..cab1da9 100644 --- a/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c +++ b/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c @@ -44,14 +44,14 @@ __ieee754_acoshl(long double x) EXTRACT_WORDS64 (lx, xlo); if(hx<0x3ff0000000000000LL) { /* x < 1 */ return (x-x)/(x-x); - } else if(hx >=0x41b0000000000000LL) { /* x > 2**28 */ + } else if(hx >=0x4370000000000000LL) { /* x >= 2**56 */ if(hx >=0x7ff0000000000000LL) { /* x is inf of NaN */ return x+x; } else return __ieee754_logl(x)+ln2; /* acosh(huge)=log(2x) */ } else if (((hx-0x3ff0000000000000LL)|(lx&0x7fffffffffffffffLL))==0) { return 0.0; /* acosh(1) = 0 */ - } else if (hx > 0x4000000000000000LL) { /* 2**28 > x > 2 */ + } else if (hx > 0x4000000000000000LL) { /* 2**56 > x > 2 */ t=x*x; return __ieee754_logl(2.0*x-one/(x+__ieee754_sqrtl(t-one))); } else { /* 1<x<2 */ |