#13134: real_double logarithm test fails due to ulp() bug
----------------------------------+-----------------------------------------
Reporter: jdemeyer | Owner: jason, jkantor
Type: defect | Status: needs_review
Priority: blocker | Milestone: sage-5.1
Component: numerical | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Jeroen Demeyer | Merged in:
Dependencies: | Stopgaps:
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Description changed by jdemeyer:
Old description:
> This is a doctest error on Solaris SPARC introduced by #12557:
> {{{
> sage -t --long -force_lib devel/sage/sage/rings/real_double.pyx
> **********************************************************************
> File
> "/home/buildbot/build/sage/mark-1/mark_full/build/sage-5.1.beta5/devel
> /sage-main/sage/rings/real_double.pyx", line 1741:
> sage: all( check_error(x) for x in sxrange(0.01, 2.00, 0.01) )
> Expected:
> True
> Got:
> False
> **********************************************************************
> }}}
>
> It turns out that the bug is actually in the `ulp()` method which returns
> a value which is a factor 2 too small. Since in all other systems except
> SPARC the RDF `log()` method is accurate up to 0.5 ulp, the tests for
> #12557 passed.
New description:
This is a doctest error on Solaris SPARC and FreeBSD introduced by #12557:
{{{
sage -t --long -force_lib devel/sage/sage/rings/real_double.pyx
**********************************************************************
File
"/home/buildbot/build/sage/mark-1/mark_full/build/sage-5.1.beta5/devel
/sage-main/sage/rings/real_double.pyx", line 1741:
sage: all( check_error(x) for x in sxrange(0.01, 2.00, 0.01) )
Expected:
True
Got:
False
**********************************************************************
}}}
It turns out that the bug is actually in the `ulp()` method which returns
a value which is a factor 2 too small. Since in all other systems (except
Solaris SPARC and FreeBSD) the RDF `log()` method is accurate up to 0.5
ulp, the tests for #12557 passed.
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13134#comment:5>
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