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Fix bug in graph.maximum_average_degree #35533

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merged 2 commits into from
Apr 23, 2023
Merged

Fix bug in graph.maximum_average_degree #35533

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8b4c981
fix bug in graph.maximum_average_degree
dcoudert Apr 18, 2023
dcddb70
Update src/sage/graphs/graph.py
dcoudert Apr 19, 2023
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21 changes: 21 additions & 0 deletions src/sage/graphs/graph.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4673,9 +4673,30 @@ def maximum_average_degree(self, value_only=True, solver=None, verbose=0):
sage: mad_g = g.maximum_average_degree(value_only=False)
sage: g.is_isomorphic(mad_g)
True

TESTS:

Check corner cases::

sage: Graph().maximum_average_degree(value_only=True)
0
sage: Graph().maximum_average_degree(value_only=False)
Graph on 0 vertices
sage: Graph(1).maximum_average_degree(value_only=True)
0
sage: Graph(1).maximum_average_degree(value_only=False)
Graph on 1 vertex
sage: Graph(2).maximum_average_degree(value_only=True)
0
sage: Graph(2).maximum_average_degree(value_only=False)
Graph on 1 vertex
"""
self._scream_if_not_simple()
g = self
if not g:
return ZZ.zero() if value_only else g.parent()()
elif not g.size():
return ZZ.zero() if value_only else g.parent()([[next(g.vertex_iterator())], []])
from sage.numerical.mip import MixedIntegerLinearProgram

p = MixedIntegerLinearProgram(maximization=True, solver=solver)
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