#18346: Easier handling of vertex labels in graph backends
-------------------------+-------------------------------------------------
Reporter: | Owner:
ncohen | Status: needs_review
Type: | Milestone: sage-6.7
enhancement | Resolution:
Priority: major | Merged in:
Component: graph | Reviewers:
theory | Work issues:
Keywords: | Commit:
Authors: | 25765bb3c4cb4c5f49e5078d7e6e3968c62310e1
Nathann Cohen | Stopgaps:
Report Upstream: N/A |
Branch: |
public/18346 |
Dependencies: |
-------------------------+-------------------------------------------------
Description changed by ncohen:
Old description:
> 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
New description:
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
--
--
Ticket URL: <http://trac.sagemath.org/ticket/18346#comment:2>
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