Date: Wed, 08 May 2019 16:53:46 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 237800] pow(3) returns inaccurate results Message-ID: <bug-237800-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=237800 Bug ID: 237800 Summary: pow(3) returns inaccurate results Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Severity: Affects Many People Priority: --- Component: misc Assignee: bugs@FreeBSD.org Reporter: khw@cpan.org Attachment #204271 text/plain mime type: Created attachment 204271 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=204271&action=edit Reproducer .c The attached essentially one-liner, program prints 0x1.431e0fae6d722p+96 on FreeBSD 13 clang version 8.0.0 (tags/RELEASE_800/final 356365) (based on LLVM 8.0.0) On Linux, it prints 0x1.431e0fae6d721p+96 a difference of 1 in the final hex digit of the mantissa. The Linux version is the correct value. We are getting identical failures on 11.2, 12.0, and Open BSD 6.4 http://www.cpantesters.org/distro/M/Math-Clipper.html?grade=3&perlmat=1&patches=2&oncpan=2&distmat=2&perlver=ALL&osname=ALL&version=1.27 I work on maintaining and extending the Perl 5 programming language. We made a change earlier in our current development cycle that improved the accuracy of converting a string representing a floating point number into an equivalent double precision C value. We now use strtod() instead of atof(). That broke the module Math::Clipper. It turns out it was relying on the imprecision of atof() to work around this pow() bug. That work around was added in May 2018. The above smoke reports rely on a volunteer network of people to do the testing. That means the coverage of a module such as Math::Clipper is spotty. Probably it's failing Open BSD in other versions of Perl, but those just didn't get tested. -- You are receiving this mail because: You are the assignee for the bug.home | help
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