[Numpy-discussion] Mysterious test_pareto failure on Travis
Tue Sep 4 15:37:35 CDT 2012
On Tue, Sep 4, 2012 at 9:17 PM, Ondřej Čertík <firstname.lastname@example.org> wrote:
> On Tue, Sep 4, 2012 at 12:41 PM, Ondřej Čertík <email@example.com> wrote:
>> On Tue, Sep 4, 2012 at 12:31 PM, Ondřej Čertík <firstname.lastname@example.org> wrote:
>>> On Tue, Sep 4, 2012 at 3:15 AM, Nathaniel Smith <email@example.com> wrote:
>>>> The last two Travis builds of master have failed consistently with the
>>>> same error:
>>>> It looks like a real failure -- we're getting the same error on every
>>>> build variant, some sort of problem in test_pareto. Example:
>>>> The obvious culprit would be the previous commit, which regenerated
>>>> mtrand.c with Cython 0.17:
>>>> What's weird, though, is that that commit passed just fine on Travis:
>>>> It's just the two commits since then that failed. But these commits
>>>> have been 1-line docstring changes, so I don't see how they could have
>>>> possibly created the problem.
>>>> Also, the test passes fine with python 2.7 on my laptop with current master.
>>>> Can anyone reproduce this failure? Any ideas what might be going on?
>>> I made this:
>>> It was me who updated the Cython file. It seemed to be working. I've
>>> added the issue
>>> to the release TODO.
>> Ok, here is how to reproduce the problem:
>> 1) install my numpy-vendor vagrant image (32 bit Ubuntu), as directed
>> in the README:
>> 2) run tests, you'll get:
> So the problem was actually introduced much earlier. Most probably it
> has never worked
> in 32bit Ubuntu 12.04. I tried for example this old commit:
> and it still fails:
> But in any case, this seems to be a problem with the actual 32bit
> Ubuntu 12.04 itself. So maybe something in gcc
> has changed that now triggers the problem.
To be clear, the mismatching value is:
-> np.testing.assert_array_almost_equal(actual, desired, decimal=15)
(Pdb) actual[1, 0]
(Pdb) desired[1, 0]
So they do match to 14 decimal points, and it's entirely possible that
this is just a problem of the test being too stringent in requiring 15
decimal points of match. Maybe the 32-bit GCC is spilling registers
differently, tripping the famous x86 idiosyncrasy where register
spilling triggers rounding. But I'd feel better if someone familiar
with the pareto code could confirm.
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