Dear Greg, dear Franco,
Short summary for the Sage-Combinat devs:
Greg is upgrading networkx to 1.0 in Sage, and this is causing some
unpickling issues for dynkin diagrams, crystals, posets, ...
Short of any good solution, I think we do not have (yet) any important
pickle of crystals or dynkin diagrams around, so keeping backward
compatibility is not a strong issue for those.
Anyone around having a large database of Poset pickles?
On Fri, Jan 29, 2010 at 03:51:37PM -0800, Greg McWhirter wrote:
> Ah, ok then, thanks. =) Found the issue and almost solved it. Added
>
> from sage.structure.sage_object import register_unpickle_override
> import networkx.classes
> register_unpickle_override('networkx.xgraph','XGraph',
> networkx.classes.Graph, call_name=('networkx.classes','Graph'))
> register_unpickle_override('networkx.xdigraph','XDiGraph',
> networkx.classes.DiGraph, call_name=('networkx.classes','DiGraph'))
>
> to the graph_backends.py
Cool!
> This will pass the tests but it still isn't quite right. The issue is
> in unpickling graphs with multiple edges. Due to the nature of the
> networkx library changes, unpickling a graph with multiple edges
> results in one without multiple edges which is broken when calling
> edges() on it.
>
> I was thinking of writing a translation class that would take whatever
> input from either of the two deprecated classes. Then, to use it,
> require the user to call a convert() method or something on it, which
> would return the proper networkx class with appropriate data. This
> seems less than ideal, however, and some sort of post-unpickle hook
> would seem better, but poking around it doesn't seem that one exists.
> I would love suggestions for other ways to solve this.
Hopefully you can hack the __setstate__ method of networkx's new
DiGraph class to fix the pickle state if it corresponds to an old
networkx pickle, and leave it as is are otherwise. If it is hard to
detect between the two, you could specify in
register_unpickle_override a function (instead of DiGraph), which
would create an empty DiGraph object with just one attribute
self._unpickling_from_networkx_0_3=True that __setstate__ could test
upon. See the pickle protocol for details:
http://docs.python.org/library/pickle.html
Just a question: are we the only one around having backward
compatibility issue in the switch from networkx 0.3 and 1.0? I would
have expected others to have already resolved this problem. Is it
just that we waited too long before trying to upgrade?
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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