digraph.diameter() returning +Infinity for some cases
I'm running Sage 6.4.1 on OS X (Yosemite). Creating a directed graph with n
vertices (for any n that I tried) returned +Infinity
. EG:
sage: digraphs.Path(10).diameter()
+Infinity
or even
sage: digraphs.ButterflyGraph(5).diameter()
+Infinity
However, both of these Path and Butterfly graphs are finite, connected, directed acyclic graphs so their diameter should always be finite.
The underlying graph is connected. But if you type: digraphs.Path(10).show() you'll see a path from 1 to 2 to 3 and so on. So there is no directed path, for example, from 2 to 1. The distance from 2 to 1 is infinite but the distance from 1 to 2 is one. The diameter is just the maximum of the distances so it has to be infinite.