#9760: Possible numerical noise doctest failure in sage/matrix/matrix2.pyx on t2
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Reporter: mpatel | Owner: drkirkby
Type: defect | Status: new
Priority: blocker | Milestone: sage-4.5.3
Component: solaris | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by jhpalmieri):
Replying to [comment:1 drkirkby]:
> I expect ATLAS would be used for this test, but has that been 100%
confirmed?
>
> It's very puzzling. I guess its possible that ATLAS may give slightly
different results if it's tuned differently.
>
> I suspect John built this with the ATLAS changes at #9508. Since he
normally used a version of ATLAS he built before to save time, I suspect
he tuned ATLAS this time.
That's right. Although my old version is based on atlas-3.8.3.p12,
compared to the current 3.8.3.p14. I also had to rebuild the shared
libraries, and I rebuilt them using exactly the commands from the p14
spkg. I don't think the ATLAS sources changed from p12 to p14, so the
only difference should be in the tuning from one time (several months ago)
to another. When I built Sage using SAGE_ATLAS_LIB pointing to my old
version, the tests passed; indeed, if I just copy the p12 files to
SAGE_ROOT/local/lib, then tests pass. If I copy the p14 files back, then
tests fail.
> It's possible that the additional shared libraries from #9508 mean
something in Sage that previously linked with a static library, would now
link with a shared one.
I don't know if it's that or if it's just different tuning from one build
to the next.
> I suspect slight differences in tuning parameters might be the cause
though. Does the criteria need to be changed by a factor of 10 to get
htis to pass, or would a maller change be acceptable,
A smaller change would work, at least right now: the largest imaginary
part for any eigenvalue is 1.09867961128e-15. With the p12 files, the
largest (in absolute value) is -4.61662881292e-16. Of course, now I see
that the doctest should really be '''abs'''(imag(e)) < 1e-15...
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9760#comment:4>
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