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From: "joseph at codesourcery dot com" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug math/16447] erfc (0x6.a8p+4) ldbl-128 throws underflow exception Date: Thu, 06 Feb 2014 16:38:00 -0000 [thread overview] Message-ID: <bug-16447-131-1XkOpTF8cs@http.sourceware.org/bugzilla/> (raw) In-Reply-To: <bug-16447-131@http.sourceware.org/bugzilla/> http://sourceware.org/bugzilla/show_bug.cgi?id=16447 --- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- On Thu, 6 Feb 2014, stli at linux dot vnet.ibm.com wrote: > unsafe = abs(n_i) >= -16363; Well, abs >= (negative value) doesn't seem right. To work out what's unsafe, you need to consider how small x22 can be in cases where ex2_u.d is small. The answer is roughly that x22, if not 0, is at least 1ulp of the input (not exactly, because of the way values from a table get subtracted from the input) - so, roughly, you could have problems up to n_i around -16382 + 113. Certainly saying unsafe = abs (n_i) >= 15000 should be safe, even allowing for the way x gets adjusted. > How to handle the unsafe-check? > Which platform uses this implementation of expl? > Can we simply change the unsafe-check in sysdeps/iee754 or is a new > platform-specific implementation required? The same correction should apply to all platforms using ldbl-128; no platform-specific implementation should be needed. -- You are receiving this mail because: You are on the CC list for the bug.
next prev parent reply other threads:[~2014-02-06 16:38 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-16447-131@http.sourceware.org/bugzilla/> 2014-02-04 16:04 ` joseph at codesourcery dot com 2014-02-06 15:57 ` stli at linux dot vnet.ibm.com 2014-02-06 16:38 ` joseph at codesourcery dot com [this message] 2014-02-11 12:53 ` cvs-commit at gcc dot gnu.org 2014-02-11 14:13 ` krebbel1 at de dot ibm.com 2014-06-13 8:58 ` fweimer at redhat dot com
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