#18346: Easier handling of vertex labels in graph backends
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Reporter: ncohen | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.7
Component: PLEASE CHANGE | Keywords:
Merged in: | Authors: Nathann Cohen
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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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
--
Ticket URL: <http://trac.sagemath.org/ticket/18346>
Sage <http://www.sagemath.org>
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