#14980: graph_generators, some more clean up
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Reporter: eisermbi | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-5.12
Component: graph theory | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Dependencies: | Stopgaps:
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While adding some graph generators I found some confusing things which I
like
to improve with this patch first.
* Why are Butterfly, Krackhardt Kite, Barbell graph listed under
"Basic Structures" while Peterson Graph and CompleteGraph are not?
Maybe the term "basic structures" is subjective and everyone has a
different opinion about basic...
* What is a "small graph"? A graph with a small number of vertices,
alright?
E.g. 13 vertices on http://www.graphclasses.org/smallgraphs.html
In general not much more than 15 or 20 vertices. Can "Balaban11Cage()"
with 112 vertices, "CameronGraph()" with 231 vertices, "Tutte12Cage()"
with 126 vertices be called "small graphs"??
Overview of modifications on the files 'sage/graphs/graph_generators.py'
and 'sage/graphs/generators/*'.
Part 1
* "Small Graphs" (also called "named graphs" previously): Added
documentation: "A small graph is just a single graph and has no parameter
influencing the number of edges or vertices."
* Families of Graphs: Added documentation: "A family of graph is an
infinite set of graphs which can be indexed by fixed number of parameters,
e.g. two parameters."
* Pseudofractal graphs: The graph "DorogovtsevGoltsevMendesGraph" seems to
be a quite special graph family. Does it need its own section? I
completely moved it to Families now.
* HararyGraph is a family of graphs.
Note that some graphs in this section are not really small! Actually, I'd
find
it better to called the section "individual graphs" (as on
https://en.wikipedia.org/wiki/Gallery_of_named_graphs) or stick with the
previous
term "named graphs". (The renaming to "small graphs" happened in #13862.
Sorry, I do not know the reason...)
Part 2
* "Platonic Solids" is a subsection of "Small graphs". This section is
ordered by number of vertices now.
* "Chessboard graphs" is a subsection of "Families".
* RandomGNP returns graph, hence, "n" -- number of nodes of the graph
(not: ''digraph'')
Note, the formatting of the references in html (of RandomGNP) looks odd?!
Don't know what is wrong or how to correct this...
Part 3
* creating "Miscellaneous" section and renaming "world_map.py" to
"miscellaneous.py"
* `cospectral_graphs`, `line_graph_forbidden_subgraphs`, `fullerences`,
`trees`
are not single graphs nor families of graphs; moving them in
"Miscellaneous";
(Alternatively, one might leave them directly under "Graph Generators"
without any section header the functions `canaug_traverse_edge`,
`canaug_traverse_vert`, `check_aut`, `check_aut_edge`...)
Part 4
* Basic structures / "Some Commonly Used Graph": Actually these graphs can
be listed in the other classes. Hence, I moved them to their corresponding
section but sometimes left copies in this section, renamed to "commonly
used graph generators".
That is,
"BarbellGraph", "CircularLadderGraph", "CycleGraph",
"CompleteBipartiteGraph",
"CompleteGraph", "CompleteMultipartiteGraph", "Grid2dGraph",
"GridGraph",
"PathGraph", "LadderGraph", "StarGraph", "ToroidalGrid2dGraph",
"Toroidal6RegularGrid2dGraph", "WheelGraph" are families of graphs.
"BuckyBall", "BullGraph", "ButterflyGraph", "ClawGraph", "DiamondGraph",
"EmptyGraph", "HouseGraph", "HouseXGraph", "KrackhardtKiteGraph",
"LollipopGraph"
are "small graphs" ("named graphs").
In other words, the most important graphs/graph families can be ''double
listed''
to make it easier to find them. Yes, "most important graphs" is, of
course,
subjective but these graphs are now double listed anyway. I would choose
graphs
that are important to new users of SAGE.
Alternatively, this section might be removed completely and the example
above might be expanded... (Maybe this would the better solution.)
* removal of file "basic.py" (some kind of deprecation needed?)
--
Ticket URL: <http://trac.sagemath.org/ticket/14980>
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