Doctest failure in sage/rings/polynomial/polynomial_element.pyx on Solaris

[jpflori]

sage -t devel/sage/sage/rings/polynomial/polynomial_element.pyx
**********************************************************************
File "devel/sage/sage/rings/polynomial/polynomial_element.pyx", line 1054, in sage.rings.polynomial.polynomial_element.Polynomial.inverse_mod
Failed example:
    parent(poly)([ 0.0 if abs(c)<=1e-14 else c for c in poly.coeffs() ])
Expected:
    1.0
Got:
    1.02140518266e-14*x^2 + 1.0
**********************************************************************
1 item had failures:
   1 of  16 in sage.rings.polynomial.polynomial_element.Polynomial.inverse_mod
    [1375 tests, 1 failure, 84.4 s]
----------------------------------------------------------------------
sage -t devel/sage/sage/rings/polynomial/polynomial_element.pyx  # 1 doctest failed
----------------------------------------------------------------------
Total time for all tests: 88.1 seconds
    cpu time: 75.4 seconds
    cumulative wall time: 84.4 seconds

It looks like there is more numerical noise than expected.
Changing 1e-14 to 1e-13 might be a sensible solution.

CC: @jdemeyer

Component: porting: Solaris

Keywords: solaris numerical noise

Reviewer: Jeroen Demeyer

Issue created by migration from https://trac.sagemath.org/ticket/14436

[jpflori]

comment:1

I've not looked at the code, so I don't know if we really expect the coefficients rounded to zero to be less than 1e-14, or if that's just an arbitrary bound which looked close enough to zero.

[jdemeyer]

Attachment: trac_10508_doctest.rebased.patch.gz

[jdemeyer]

Author: Jeroen Demeyer

[jpflori]

comment:3

Please note this happened with ATLAS 3.10.1.p0 from #10508 which may be used in the linear algebra step of the algorithm.

And the bound seems quite random, at least there is no justification for this choice, nor a precise error bounding stated anywhere.

[jdemeyer]

Changed author from Jeroen Demeyer to none

[jdemeyer]

comment:4

Replying to @jpflori:

Please note this happened with ATLAS 3.10.1.p0 from #10508

In that case, the problem is already fixed by a patch on that ticket.

[jdemeyer]

Reviewer: Jeroen Demeyer

[jpflori]

comment:6

Oh yeah, really sorry about that...
I completely forgot to install the Sage library patches on this system...