New non-existence tests for strongly regular graphs

[nathanncohen]

This branch adds more infeasibility tests from the following paper:

http://www.win.tue.nl/~aeb/preprints/srgsurvey.pdf

Nathann

Depends on #18960

CC: @dimpase

Component: graph theory

Author: Nathann Cohen

Branch/Commit: 9d85b97

Reviewer: Jori Mäntysalo

Issue created by migration from https://trac.sagemath.org/ticket/18982

[nathanncohen]

Branch: u/ncohen/18982

[nathanncohen]

Commit: 6d72675

[nathanncohen]

New commits:

a0173e2	trac #18948: Strongly Regular Graphs database
4adcf95	trac #18948: Two missing graphs
cf50d70	trac #18948: Merged with 6.8
6390dd9	trac #18960: Strongly Regular Graphs from two-weight codes
3eee1e7	trac #18960: Merge 6.9.beta0
606d15f	trac #18960: Adding nonzero somewhere
83ed332	trac #18960: Again...
dc2d326	trac #18960: Lint -> vLint
4fb3ce1	CURRENT
6d72675	trac #18982: New non-existence tests for strongly regular graphs

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

d9bb797

trac #18982: New non-existence tests for strongly regular graphs

[sagetrac-git]

Changed commit from 6d72675 to d9bb797

[sagetrac-git]

Changed commit from d9bb797 to 938c769

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

938c769

trac #18982: New non-existence tests for strongly regular graphs

[jm58660]

comment:4

Needs rebasing again.

Also when I did raise SomeError('An error occurred.') I got a comment that it should be raise SomeError('an error occurred'). (Which seems stupid to my eyes, but is in some PEP.)

[sagetrac-git]

Changed commit from 938c769 to 9d85b97

[sagetrac-git]

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

9d85b97

trac #18982: Merged with 6.9.beta1

[nathanncohen]

comment:6

Needs rebasing again.

Done.

Also when I did raise SomeError('An error occurred.') I got a comment that it should be raise SomeError('an error occurred'). (Which seems stupid to my eyes, but is in some PEP.)

I do not see the point of that either. I hope that your reviewer will not stop here then :-p

Nathann

[jm58660]

comment:8

Replying to @nathanncohen:

I hope that your reviewer will not stop here then :-p

This is free for Somebody Other(tm) to review... I will add my name to reviewers-field if I make significant progress with reading this.

[jm58660]

comment:9

Well, was not that hard.

Assuming other parts work, this seems to be direct (and correct) translation of equations from the paper to the code. I read it, and tested with examples given in the paper. I think that l as a variable name makes sense here, because lambda is already reserved name (and we do not use Fortress language :=)), even if it violates PEP 0008 part "Names to Avoid". Hence I mark this as positive review.

Btw, graphs.strongly_regular_graph(324,57,0,12) says "- - graph exists.Comments: - -", i.e. has a missing space. You may want to correct it, when next time modifying this file.

[jm58660]

Reviewer: Jori Mäntysalo

[dimpase]

comment:10

yeah, lambda as a variable name might get you confused...

PS. The tests in the reference are hardly new, I changed wording there.

[nathanncohen]

comment:11

Well, was not that hard.

Thanks for the review!

Btw, graphs.strongly_regular_graph(324,57,0,12) says "- - graph exists.Comments: - -", i.e. has a missing space. You may want to correct it, when next time modifying this file.

Done in #19019.

Nathan

[vbraun]

Changed branch from u/ncohen/18982 to 9d85b97