Opened 6 years ago

Closed 6 years ago

#15572 closed defect (fixed)

Exceptions when multiedges/loops are not supported

Reported by: ncohen Owned by:
Priority: major Milestone: sage-6.1
Component: graph theory Keywords:
Cc: azi, combinat, nthiery, dcoudert Merged in:
Authors: Nathann Cohen Reviewers: Jean-Baptiste Priez
Report Upstream: N/A Work issues:
Branch: u/ncohen/15572 (Commits) Commit: 606221c3868cdb2df84654ec92756469c9836d18
Dependencies: Stopgaps:

Description

Some Graph functions are not made to handle non-simple graphs, i.e. graphs containing loops or multiple edges. This ticket adds necessary exceptions from place to place, hoping no error remains ignored.

The exception advises the user to remove loops/multiple edges from his graph and try again (and to update the function if he thinks that not supporting non-simple graphs is a mistake) :-P

This has been reported on sage-support fairly recently [1], and thousands of times before. Past time to deal with those wrong answers :-/

[1] ​https://groups.google.com/d/msg/sage-support/bsXYMXwgW5w/LPrmCNGoah0J

Change History (9)

comment:1 Changed 6 years ago by ncohen

  • Branch set to u/ncohen/15572
  • Commit set to 843473a223c0eaaaf02175df8a34d83fc05125da
  • Status changed from new to needs_review

New commits:

​843473atrac #15572: Exceptions when multiedges/loops are not supported

comment:2 Changed 6 years ago by ncohen

Looks like DiGraph.is_directed_acylic actually has no problems with loops. The exception broke a doctest in rings/semirings/non_negative_integer_semiring.py.

Fixed !

Nathann

comment:3 Changed 6 years ago by git

  • Commit changed from 843473a223c0eaaaf02175df8a34d83fc05125da to b7f01c979aa1e16b1295b6673cd1fdc7f3de7740

Branch pushed to git repo; I updated commit sha1. New commits:

​b7f01c9trac #15572: DiGraph.is_directed_acyclic handles loops pretty well
​3bf44batrac #15572: Rebase on 6.1.beta2

comment:4 Changed 6 years ago by elixyre

  • Reviewers set to elixyre
  • Status changed from needs_review to positive_review

comment:5 Changed 6 years ago by elixyre

  • Reviewers changed from elixyre to Jean-Baptiste Priez

comment:6 Changed 6 years ago by vbraun

  • Status changed from positive_review to needs_work

Doctest failures: 

sage -t --long src/sage/graphs/digraph.py
**********************************************************************
File "src/sage/graphs/digraph.py", line 1035, in sage.graphs.digraph.DiGraph.is_directed_acyclic
Failed example:
    g.allow_loops(True)
Exception raised:
    Traceback (most recent call last):
      File "/mnt/SSD1/mod_buildslave/sage_git/build/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 480, in _run
        self.execute(example, compiled, test.globs)
      File "/mnt/SSD1/mod_buildslave/sage_git/build/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 839, in execute
        exec compiled in globs
      File "<doctest sage.graphs.digraph.DiGraph.is_directed_acyclic[11]>", line 1, in <module>
        g.allow_loops(True)
    NameError: name 'g' is not defined
**********************************************************************

comment:7 Changed 6 years ago by ncohen

  • Commit b7f01c979aa1e16b1295b6673cd1fdc7f3de7740 deleted
  • Status changed from needs_work to needs_review

Sorry 'bout that. Just fixed it by updating the last commit.

Nathann

comment:8 Changed 6 years ago by git

  • Commit set to 606221c3868cdb2df84654ec92756469c9836d18

Branch pushed to git repo; I updated commit sha1. New commits:

​606221ctrac #15572: DiGraph.is_directed_acyclic handles loops pretty well
​3bf44batrac #15572: Rebase on 6.1.beta2
​843473atrac #15572: Exceptions when multiedges/loops are not supported

comment:9 Changed 6 years ago by vbraun

  • Resolution set to fixed
  • Status changed from needs_review to closed
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