Re: [PATCH 4/4] gnu: matplotlib: Add gtk3 backends.

[Federico Beffa <beffa@ieee.org>]

On Tue, Dec 23, 2014 at 1:17 AM, Ludovic Courtès <ludo@gnu.org> wrote:
> I found that “guix build python2-matplotlib -n” triggers a seemingly
> infinite loop (either uses of ‘package-with-python2’ somehow introduce
> cycles, or they lead to very large DAGs), which is what is causing Hydra
> evaluation failures.
>
> I tried reverting 25f9a0 but it doesn’t help.
>
> Could you try to bisect it and revert or fix the problem?  If it turns
> out to require more time, could you just comment out the offending parts
> of python.scm so Hydra can resume?

The build does finish as I've tested it on my machine before
committing the package. However, for some reason, guix needs very long
to generate the derivation. On my machine (quad-core Xeon E5520)
python2-matplotlib takes ca. 31 mins to start building.
Python2-scipy, which includes python2-matplotlib, takes ca. 80 mins.!
Currently I do not understand the reason, but I note that matplotlib,
numpy and scipy are the only python packages with a large number of
inputs.

I've tried to use trace in the REPL and I see that there is a very
large activity about inputs and their origins. However, the buffer
just becomes too large to handle. It needs more sophisticated
debugging methods.

For the moment I've commented out python2-matplotlib and the python-2
versions of the packages making use of it: scipy and numpy.

Sorry for the inconvenience!  I did not expect that this would cause
troubles to hydra.
Fede