id,summary,reporter,owner,description,type,status,priority,milestone,component,resolution,keywords,cc,merged,author,reviewer,upstream,work_issues,branch,commit,dependencies,stopgaps
18346,Easier handling of vertex labels in graph backends,ncohen,,"This ticket addresses the following problem:
In the `CGraph` backends, three `cdef` functions are used all the time to
deal with vertex labels, i.e. `get_vertex`, `vertex_label`,
`check_vertex`. They are always called with the same arguments, which are
all attributes of the backend that calls it. They should be method, so that
the arguments are not needlessly repeated.
What this branch does:
- The `CGraph` backends (i.e. `SparseBackend`, `DenseBackend` and
`StaticSparseGraph`) and `GenericGraphBackend` are turned into cdef classes.
- The three functions `get_vertex`, `vertex_label`, `check_vertex` become
methods of `CGraphBackend`
- It adds a method `CGraphBackend.c_graph()` to get the two cdef attributes
`_cg` and `_cg_rev`. Turns out that some code in Sage accesses directly
`G._backend._cg`.
This should have been sufficient, but there were (unexpected) consequences:
- There is no automatic pickling for cdef classes (as instrospection does not
work), and the doctests do not pass if that does not work. Consequently, I
implemented a unique `__reduce__` function in `GenericGraphBackend` which
handles the pickling for all backends (sparse/dense/static/networkx). It also
removes some duplicated code as a result.
This makes the code a bit clearer (and it is needed). Also, moving this pickling
function above is good for the future, for there will be many modifications in
the future to the data structures in Sage: I plan to merge `CGraph` and
`GenericBackend` into only one class (but that's for later).
Nathann
P.S.: The branch is built to be reviewed commit by commit. In particular, the renamed file appears as trivial when looking at the first commit, but as a lot of + and - when looking at the branch's diff",enhancement,closed,major,sage-6.7,graph theory,fixed,,borassi dcoudert darij vdelecroix,,Nathann Cohen,Vincent Delecroix,N/A,,6ffbb05999f70fa2535f28aca08b203036664491,6ffbb05999f70fa2535f28aca08b203036664491,#18317,