diff --git a/src/sage/graphs/digraph_generators.py b/src/sage/graphs/digraph_generators.py index 618babd4637..21dbd01ca70 100644 --- a/src/sage/graphs/digraph_generators.py +++ b/src/sage/graphs/digraph_generators.py @@ -403,9 +403,10 @@ def RandomTournament(self, n): .. SEEALSO:: - * :meth:`~sage.graphs.digraph_generator.DiGraphGenerators.Complete` + - :meth:`~sage.graphs.digraph_generators.DiGraphGenerators.Complete` + + - :meth:`~sage.graphs.digraph_generators.DiGraphGenerators.RandomSemiComplete` - * :meth:`~sage.graphs.digraph_generator.DiGraphGenerators.RandomSemiComplete` """ from sage.misc.prandom import random g = DiGraph(n) @@ -548,9 +549,9 @@ def Complete(self, n, loops=False): .. SEEALSO:: - * :meth:`~sage.graphs.digraph_generator.DiGraphGenerators.RandomSemiComplete` + - :meth:`~sage.graphs.digraph_generators.DiGraphGenerators.RandomSemiComplete` - * :meth:`~sage.graphs.digraph_generator.DiGraphGenerators.RandomTournament` + - :meth:`~sage.graphs.digraph_generators.DiGraphGenerators.RandomTournament` """ G = DiGraph(n, name="Complete digraph"+(" with loops" if loops else ''), loops=loops) @@ -1262,9 +1263,17 @@ def RandomSemiComplete(self, n): r""" Return a random semi-complete digraph on `n` vertices. - A directed graph `G=(V,E)` is ``semi-complete`` if for any pair of - vertices `u` and `v`, *at least* one edge of ``uv`` and ``vu`` is in - ``E``. + A directed graph `G=(V,E)` is *semi-complete* if for any pair of + vertices `u` and `v`, there is *at least* one arc between them. + + To generate randomly a semi-complete digraph, we have to ensure, for any + pair of distinct vertices `u` and `v`, that with probability `1/3` we + have only arc `uv`, with probability `1/3` we have only arc `vu`, and + with probability `1/3` we have both arc `uv` and arc `vu`. We do so by + selecting a random integer `coin` in `[1,3]`. The case *only `uv`* + corresponds to `coin==1`, the case *only `vu`* to `coin==3`, and the + case *both* to `coin==2`. + INPUT: @@ -1283,9 +1292,9 @@ def RandomSemiComplete(self, n): .. SEEALSO:: - * :meth:`~sage.graphs.digraph_generator.DiGraphGenerators.Complete` + - :meth:`~sage.graphs.digraph_generators.DiGraphGenerators.Complete` - * :meth:`~sage.graphs.digraph_generator.DiGraphGenerators.RandomTournament` + - :meth:`~sage.graphs.digraph_generators.DiGraphGenerators.RandomTournament` """ G = DiGraph(n, name="Random Semi-Complete digraph")