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strongly_regular_graph() crashes when mu=0 #19712
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New commits:
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Commit: |
Branch: public/19712 |
comment:2
I presume you're not changing the definition, i.e. you still allow mu=0, right? |
comment:3
Well, is mu=0 allowed for strongly regular graphs? If they are assumed to be connected + non-complete, then mu>0 isn't it? Nathann |
comment:4
Replying to @nathanncohen:
Well, either we require that the graph AND its complement are connected, or we live with mu=0. Don't we have mu=0 in 6.9? If yes, we'd need to do deprecation to switch to mu>0... I'd rather keep mu=0 - the classification of graphs in this case is trivial. |
comment:5
Okayokay. Can you update the branch then? Nathann |
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
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comment:7
Unless you agree with that ? Nathann |
comment:8
here is a problem; not everything to do with strong regularity goes through the function you just changed:
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comment:9
because of the latter, I always thought that Sage does allow mu=0... Also, note the docs of |
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
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comment:12
if we allow mu=0 then the disjoint union of m copies of |
comment:13
The wikipedia page says that often both are excluded, i.e. both the disjoint complete graphs and the complete bipartite graphs. Now, my former patch excluded both and you complained about it. Now, you seem to complain that I only exclude one of the two. Make up your mind. Nathann |
comment:14
well, I am OK with anything that makes It looks easier after all to make |
comment:15
or allow mu=0, but make sure that _check_database() does not count these graphs. |
comment:16
well, let me know whether you like me to fix the patch, or rather do it yourself? |
comment:17
If you have time to deal with it today I certainly won't mind |
comment:18
Replying to @nathanncohen:
OK, will do. |
comment:20
OK, ready for review! |
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Changed author from Nathann Cohen to Nathann Cohen, Dima Pasechnik |
comment:23
Looks good to me. I don't like the 'mu=0' much, given that it actually "isn't defined" but well, that's life. Well. What would you think of testing As you like. Nathann |
comment:24
Replying to @nathanncohen:
I don't see what do you mean when you say "the undefined 'mu'". Do you mean that it is an optional parameter? But it is uniquely determined by the other parameters, so it's not what I call "undefined"... |
comment:25
Oh, sorry. I meant that for complete graphs it is undefined. But indeed it is not 'as bad' as I thought. No problem then. I'll run the tests and change this ticket's status. Thanks. Nathann |
Reviewer: Nathann Cohen, Dima Pasechnik |
comment:27
Great, thanks! Hopefully it can get into 6.10, still... |
Changed branch from public/19712 to |
Reported by Georgi Guninski:
(and more of these).
This is because of a "%0" and "/0" in the code in several places. Which happened, as it was confusion over the corner cases mu=0 and mu=k.
CC: @dimpase
Component: graph theory
Author: Nathann Cohen, Dima Pasechnik
Branch/Commit:
03c0c20
Reviewer: Nathann Cohen, Dima Pasechnik
Issue created by migration from https://trac.sagemath.org/ticket/19712
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