This is the mail archive of the
glibc-bugs@sourceware.org
mailing list for the glibc project.
[Bug math/14868] New: ldbl-128ibm hypotl inaccurate for arguments differing by 2^60
- From: "jsm28 at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Wed, 21 Nov 2012 23:34:13 +0000
- Subject: [Bug math/14868] New: ldbl-128ibm hypotl inaccurate for arguments differing by 2^60
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=14868
Bug #: 14868
Summary: ldbl-128ibm hypotl inaccurate for arguments differing
by 2^60
Product: glibc
Version: 2.16
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: unassigned@sourceware.org
ReportedBy: jsm28@gcc.gnu.org
Classification: Unclassified
Host: powerpc*
The ldbl-128ibm implementation of hypotl returns a+b if the absolute values of
the arguments have a ratio of over 2^60. But while in such a case it's true
that the round-to-nearest result will be the larger absolute value of an
argument, a+b isn't the correct way to compute that result, and results in
large errors until the ratio is over 2^106. For example, hypotl (1.0L,
0x1p-61L) has a 17592186044416 ulp error (as computed using libm-test.inc).
This appears to be what's causing 16 ulp errors for csqrtl tests as well.
--
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.