#18317: General documentation about graph data structures
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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: | b7d90367738afb7bfcf2d97701451fccbeebf31f
Nathann Cohen | Stopgaps:
Report Upstream: N/A |
Branch: |
public/18317 |
Dependencies: |
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Comment (by ncohen):
Hello,
> In `src/sage/graphs/base/overview.py`, you mention digraphs, but you
seem to say nothing about them.
I always talk about both. From time to time I said "graph and digraph",
but if I need to be politically correct and do not make one side feel like
(s)he is neglected I added "(di)graph" everywhere.
> "Supports: addition/removal of edges/vertices available": remove the
"available"?
Right, done. I hesitated between different versions of this text, and this
was a leftover.
> "ligther" should be "lighter".
Done.
> There is yet another distinction that is often left implicit but needs
to be clarified here
Well, it's not really related to the data structure
> In a graph, the edges can be either just predicates saying that "vertex
`a` is connected to vertex `b`, (possibly) with edge label `l`", or they
can be mathematical objects on their own rights. The difference is most
obvious when you have two edges with the same label both from a vertex `a`
to a vertex `b`. Are these two edges equal or not?
There is no "edge" object in Sage. So asking whether they are equal is
almost philosophy `:-)`
The label of an edge, however, can be any data that you like. So if you
need edges to be more complicated objects, you can store it there.
> A doc should make clear which of them is supported by which class.
Edge labels are "not very compatible" with a dense data structure, and for
those it is claimed that edge labels are not supported. For sparse graphs
arbitrary edge labels are supported.
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/18317#comment:4>
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