Approximate minimum feedback vertex set #2316
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cc @JamesClough |
JamesClough
reviewed
Dec 5, 2016
| # weights of all nodes. | ||
| except StopIteration: | ||
| gamma = min(weights[v] / (d - 1) for v, d in G.degree()) | ||
| weights -= {v: gamma * (d - 1) for v, d in G.degree()} |
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Tried running this to see what the problem was - my problem (running Python 2.7 - don't know if this is different in other versions) was this line where we're trying to subtract a dictionary from a Counter. Was this dictionary meant to be a Counter as well?
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This actually works on Python 3, but not on Python 2 it seems.
JamesClough
reviewed
Dec 5, 2016
| # approximation guarantee. | ||
| while stack: | ||
| v = stack.pop() | ||
| if nx.is_forest(G_original.subgraph(F - {v})): |
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Here we're checking whether the FVS minus vertex v is a forest - but shouldn't we actually be checking whether the original graph minus (FVS - v) is a forest?
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@JamesClough You are correct in both of your comments, I'll make those changes and try again. |
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Improved implementation of pull request #2279; fixes issue #2270.
Currently does not work but I'm not sure why. It's kind of a pain to debug. Hopefully someone can figure it out.