Bug 2540

Summary:	Incorrect return from float acosh (0X1.01FB0B7471C13P+0)
Product:	glibc	Reporter:	H.J. Lu <hjl.tools>
Component:	math	Assignee:	Not yet assigned to anyone <unassigned>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	drepper.fsp, glibc-bugs
Priority:	P2	Flags:	fweimer: security-
Version:	unspecified
Target Milestone:	---
Host:	x86_64-unknown-linux-gnu	Target:	x86_64-unknown-linux-gnu
Build:	x86_64-unknown-linux-gnu	Last reconfirmed:

Description H.J. Lu 2006-04-12 22:05:35 UTC

Failure: Test: acosh (0X1.01FB0B7471C13P+0) == 0X1.FD303BDCD51D2P-4
Result:
 is:          1.24313831329345703125e-01   0x1.fd308000000000000000p-4
 should be:   1.24313578009605407715e-01   0x1.fd303c00000000000000p-4
 difference:  2.53319740295410156250e-07   0x1.10000000000000000000p-22
 ulp       :  34.0000
 max.ulp   :  0.0000

Comment 1 Ulrich Drepper 2006-04-23 17:48:55 UTC

Suspended until somebody comes up with a patch.

Comment 2 Joseph Myers 2012-02-19 18:05:29 UTC

When that argument is rounded to float it's 0X1.01FB0CP+0 and the correctly rounded result is 0X1.FD3082P-4.  So this is a 1ulp error, not 34ulp.  (Since there are no testcases in the testsuite expecting any error from acoshf, we should still add that actual float value to the testsuite.)

Comment 3 Joseph Myers 2012-10-24 12:44:26 UTC

Collecting all reports of few-ulps errors together in one meta-bug.

*** This bug has been marked as a duplicate of bug 14759 ***