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From: "jsm28 at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug math/14783] New: Incorrect subnormal fma results in non-default rounding modes Date: Mon, 29 Oct 2012 23:56:00 -0000 [thread overview] Message-ID: <bug-14783-131@http.sourceware.org/bugzilla/> (raw) http://sourceware.org/bugzilla/show_bug.cgi?id=14783 Bug #: 14783 Summary: Incorrect subnormal fma results in non-default rounding modes Product: glibc Version: 2.16 Status: NEW Severity: normal Priority: P2 Component: math AssignedTo: unassigned@sourceware.org ReportedBy: jsm28@gcc.gnu.org Classification: Unclassified The various fma implementations have logic for scaling down results, in the case of subnormal results that are at least half the smallest positive normal value in magnitude, that assumes round-to-nearest and so is incorrect in other rounding modes. (The code at fault is the same as in bug 14152, but from the user perspective they are separate bugs, missing exceptions (any rounding mode) versus incorrect results (non-default rounding modes).) For example, on x86, fmal (0x1.4p-16382L, 0x1.0000000000000004p-1L, 0x1p-16384L) returns 0x7.000000000000001p-16385L independent of rounding mode, but this should be 0x7.000000000000002p-16385L in FE_UPWARD mode. Working on a patch. -- 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.
next reply other threads:[~2012-10-29 23:56 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-10-29 23:56 jsm28 at gcc dot gnu.org [this message] 2012-10-30 13:57 ` [Bug math/14783] " jsm28 at gcc dot gnu.org 2014-06-14 11:17 ` fweimer at redhat dot com
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