#16210: Bug in is_hamiltonian: wrong exceptions are caught
-------------------------+-------------------------------------------------
Reporter: | Owner:
ncohen | Status: needs_review
Type: | Milestone: sage-6.2
defect | Resolution:
Priority: major | Merged in:
Component: graph | Reviewers: Vincent Delecroix
theory | Work issues:
Keywords: | Commit:
Authors: | d69303cb818b864cc4d2ac95ccfb17f4cf9bf375
Nathann Cohen | Stopgaps:
Report Upstream: N/A |
Branch: |
u/ncohen/16210 |
Dependencies: |
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Changes (by vdelecroix):
* reviewer: => Vincent Delecroix
Old description:
> {{{
> g=graphs.CycleGraph(10)
> sage: g.allow_loops(True)
> sage: g.add_edge(0,0)
> sage: g.is_hamiltonian()
> False
> }}}
>
> This happens because in `traveling_salesman_problem` the call to
> `_scream_is_not_simple` raises a `ValueError` when the graph is not
> simple, and the same exception is raised when the graph is not
> hamiltonian.
>
> We can use the `EmptySetError` to differentiate them, as we cannot
> optimize anything on an empty set.
>
> Nathann
New description:
{{{
sage: g = graphs.CycleGraph(10)
sage: g.allow_loops(True)
sage: g.add_edge(0,0)
sage: g.is_hamiltonian()
False
}}}
This happens because in `traveling_salesman_problem` the call to
`_scream_is_not_simple` raises a `ValueError` when the graph is not
simple, and the same exception is raised when the graph is not
hamiltonian.
We can use the `EmptySetError` to differentiate them, as we cannot
optimize anything on an empty set.
Nathann
--
Comment:
Hi Nathann,
Why not a `NonImplementedError` (with a shorter message)?
Vincent
--
Ticket URL: <http://trac.sagemath.org/ticket/16210#comment:4>
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