Bug 2555 - Incorrect return from float yn (2, 0X1.B12ED58FD5169P+1)
Summary: Incorrect return from float yn (2, 0X1.B12ED58FD5169P+1)
Status: NEW
Alias: None
Product: glibc
Classification: Unclassified
Component: math (show other bugs)
Version: unspecified
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2006-04-12 22:33 UTC by H.J. Lu
Modified: 2019-04-10 09:15 UTC (History)
3 users (show)

See Also:
Host: x86_64-unknown-linux-gnu
Target: x86_64-unknown-linux-gnu
Build: x86_64-unknown-linux-gnu
Last reconfirmed:
fweimer: security-

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Description H.J. Lu 2006-04-12 22:33:38 UTC 
Failure: Test: yn (2, 0X1.B12ED58FD5169P+1) == -0X1.6541FD948522FP-58
Result:
 is:          5.96046447753906250000e-08   0x1.00000000000000000000p-24
 should be:  -4.84174579203368124914e-18  -0x1.6541fe00000000000000p-58
 difference:  5.96046447753906250000e-08   0x1.00000000000000000000p-24
 ulp       :  144115188075855872.0000
 max.ulp   :  0.0000
Comment 1 Ulrich Drepper 2006-04-23 17:53:26 UTC 
Suspended until somebody comes up with a patch.
Comment 2 Joseph Myers 2012-02-23 22:33:19 UTC 
When that argument is rounded to float the correct result becomes 0x1.663952P-26.  But the result glibc gives is still 0X1P-24, so confirmed (though I don't know how practical getting this very accurate is).
Comment 3 Paul Zimmermann 2014-01-22 17:24:56 UTC 
for n=42, x=0x1.0c2d26p+9, rnd=RNDZ I get an error of -62183 ulps with glibc 2.18.90 (see http://www.loria.fr/~zimmerma/glibc/).

Paul