#14532 closed enhancement (fixed)
Symplectic graphs
Reported by: | Nathann Cohen | Owned by: | jason, ncohen, rlm |
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Priority: | major | Milestone: | sage-5.10 |
Component: | graph theory | Keywords: | strongly regular graphs |
Cc: | Jernej Azarija | Merged in: | sage-5.10.beta4 |
Authors: | Nathann Cohen | Reviewers: | Frédéric Chapoton |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | #14217 | Stopgaps: |
Description (last modified by )
Brand new pretty graphs :-P
Nathann
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Attachments (3)
Change History (32)
comment:1 Changed 9 years ago by
Status: | new → needs_review |
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comment:3 Changed 9 years ago by
Helloooooooooooooo !!
Sry for comming back at you so late. I had some other stuff lately!
Come on, I am already very thankful that you take the time to review these patches !!!
- Maybe we should check if d is even and also nonzero (perhaps >= 2) since that is also a invalid parameter.
Done
- I would change the line
Graph([map(tuple,PV), lambda x,y:V(x)*(M*V(y)) == 0], loops = False) }}} to {{{ {{{ Graph((map(tuple,PV), lambda x,y:V(x)*(M*V(y)) == 0), loops = False) }}} }}} which should be 2x faster.
O_o
Here is what I get when I change it :
sage: graphs.SymplecticGraph(4,4) ... NetworkXError: Input is not a known data type for conversion.
But what do you think it should do, and why do you think that it should be 2x faster ? O_o
Nathann
comment:4 Changed 9 years ago by
I may be shooting random nonsense of course but in general it is much better to not create lists [] but iterators (). Since in the former case a list has to first be created (1 for loop) and then iterated over (2 for loop). Example
sage: %timeit max((i for i in xrange(100))) 100000 loops, best of 3: 14.5 us per loop sage: %timeit max([i for i in xrange(100)]) 10000 loops, best of 3: 30 us per loop
and even faster in this case would be
sage: %timeit 99 1000000 loops, best of 3: 429 ns per loo
comment:5 Changed 9 years ago by
Yepyep but no list is created in this case. A list of size 2 is given to the Graph constructor : the first element is a list of vertices, the second element is a function that gives adjacent pairs.
Nathann
comment:6 Changed 9 years ago by
Oh FML you see sometimes I do shoot random nonsense!
In this case the patch is ofc OK. If I were to do this I would make the additional test check (since we're already doing them) but its fine as is as well.
comment:8 Changed 9 years ago by
there is a typo in "simplectic" at least twice
Arggggggggg... Fixed :-P
Most probably because of that cursed sImplex :-P
Nathann
Changed 9 years ago by
Attachment: | trac_14532.patch added |
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comment:9 Changed 9 years ago by
hello,
if you are happy with my review patch (just removing unused imports), you can set a positive review on my behalf.
Changed 9 years ago by
Attachment: | trac_14532_review-fc.patch added |
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comment:10 Changed 9 years ago by
Keywords: | strongly regular graphs added |
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Reviewers: | → Frédéric Chapoton |
comment:11 Changed 9 years ago by
Status: | needs_review → positive_review |
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All tests pass ! Thank you very much for your help :-)
Nathann
comment:12 Changed 9 years ago by
Status: | positive_review → needs_work |
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sage -t devel/sage/sage/graphs/generators/families.py ********************************************************************** File "devel/sage/sage/graphs/generators/families.py", line 1992, in sage.graphs.generators.families.SymplecticGraph Failed example: g = graphs.SymplecticGraph(6,2) Exception raised: Traceback (most recent call last): File "/mazur/release/merger/sage-5.10.beta3/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 466, in _run self.execute(example, compiled, test.globs) File "/mazur/release/merger/sage-5.10.beta3/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 825, in execute exec compiled in globs File "<doctest sage.graphs.generators.families.SymplecticGraph[0]>", line 1, in <module> g = graphs.SymplecticGraph(Integer(6),Integer(2)) File "/mazur/release/merger/sage-5.10.beta3/local/lib/python2.7/site-packages/sage/graphs/generators/families.py", line 2000, in SymplecticGraph from sage.schemes.generic.projective_space import ProjectiveSpace ImportError: No module named projective_space **********************************************************************
comment:13 Changed 9 years ago by
Dependencies: | → #14217 |
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Changed 9 years ago by
Attachment: | trac_14532-rebased.patch added |
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comment:14 Changed 9 years ago by
Description: | modified (diff) |
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comment:16 Changed 9 years ago by
Merged in: | → sage-5.10.beta4 |
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Resolution: | → fixed |
Status: | positive_review → closed |
comment:17 follow-up: 18 Changed 9 years ago by
maybe Sage should have "polar space" graphs in general, not, only symplectic ones?
comment:18 follow-up: 19 Changed 9 years ago by
Helloooooooo !
maybe Sage should have "polar space" graphs in general, not, only symplectic ones?
Well, yes it would be nice indeed, but I do not know how to build them. I guess that it only takes 5~6 lines, like for the symplectic ones, but I don't know which ones. Actually, I have no idea on earth what these graphs are, except what I could read (and understand, which is even less) from Brouwer's website.
http://www.win.tue.nl/~aeb/graphs/srg/srgtab.html
I believe I created what he calls a VO^-
graph (graphs.BrouwerHaemersGraph
), and the same code worked for different parameters but I was not able to make it work in characteristic two, and so I did not write this more general patch.
If you know how to make it work, I would be glad to see it in Sage too :-P
Nathann
comment:19 follow-up: 29 Changed 9 years ago by
Replying to ncohen:
Helloooooooo !
maybe Sage should have "polar space" graphs in general, not, only symplectic ones?
Well, yes it would be nice indeed, but I do not know how to build them. I guess that it only takes 5~6 lines, like for the symplectic ones, but I don't know which ones. Actually, I have no idea on earth what these graphs are, except what I could read (and understand, which is even less) from Brouwer's website.
http://www.win.tue.nl/~aeb/graphs/srg/srgtab.html
I believe I created what he calls a
VO^-
graph (graphs.BrouwerHaemersGraph
), and the same code worked for different parameters but I was not able to make it work in characteristic two, and so I did not write this more general patch.
no, these are different species. I mean classical polar spaces as introduced by J.Tits (or even long before him). See e.g. Sect 6.5 of http://www.maths.qmul.ac.uk/~pjc/pps/pps6.pdf
To construct these, you need to be able to create the corresponding forms, which are well-studied by group theory, as they lead to finite classical groups. GAP has code to create these forms; it's not completely trivial in characteristic two. You can actually just call GAP! E.g.
gap> Display(InvariantQuadraticForm(GO(1,6,2)).matrix); . 1 . . . . . . . . . . . . . 1 . . . . . . . . . . . . . 1 . . . . . . gap> Display(InvariantQuadraticForm(GO(-1,6,2)).matrix); . 1 . . . . . . . . . . . . 1 1 . . . . . 1 . . . . . . . 1 . . . . . . gap> Display(InvariantSesquilinearForm(GU(6,2)).matrix); . . . . . 1 . . . . 1 . . . . 1 . . . . 1 . . . . 1 . . . . 1 . . . . .
etc...
comment:20 follow-up: 21 Changed 9 years ago by
The more one goes down this road, the more the lack of a proper backend for graphs with big automorphism groups shows. Perhaps we can try implement something next month in Paris.
comment:21 follow-up: 22 Changed 9 years ago by
The more one goes down this road, the more the lack of a proper backend for graphs with big automorphism groups shows. Perhaps we can try implement something next month in Paris.
Ahahah. Well, why not ? But I really know next to nothing about those, and what people use them for :-)
Nathann
comment:22 follow-up: 23 Changed 9 years ago by
Replying to ncohen:
The more one goes down this road, the more the lack of a proper backend for graphs with big automorphism groups shows. Perhaps we can try implement something next month in Paris.
Ahahah. Well, why not ? But I really know next to nothing about those, and what people use them for
:-)
it's useful to
- store the graphs more compactly
- compute their properties faster
Isn't it obvious? All these graphs you construct lately have huge automorphism groups, often arc-transitive and/or distance-transitive.
comment:23 follow-up: 25 Changed 9 years ago by
Isn't it obvious?
What do you use them for ? What do you want to compute ? Graphs have a lot of method, you know.. :-P
Nathann
comment:24 Changed 9 years ago by
By the way, and because these graphs are usually immutable (and dense), I wrote a couple of C functions (#14589) to store very compactly an adjacency matrix. Of course it cannot compare with an encoding by generators of the automorphism group, but a graph on 30 000 vertices can be stored on 128MB.
Nathann
comment:25 follow-up: 26 Changed 9 years ago by
Replying to ncohen:
Isn't it obvious?
What do you use them for ? What do you want to compute ? Graphs have a lot of method, you know..
:-P
Obviously, regularity properties - and this is very fast with such data. Then, e.g., e.g. maximum cliques, or an optimal colouring. It's downright hopeless to do without taking symmetries into account. Or Lovasz theta number...
comment:26 follow-up: 27 Changed 9 years ago by
Obviously, regularity properties - and this is very fast with such data. Then, e.g., e.g. maximum cliques, or an optimal colouring. It's downright hopeless to do without taking symmetries into account. Or Lovasz theta number...
Hmmm... Looks like you will have an awful amount of code to write :-P
Nathann
comment:27 Changed 9 years ago by
Replying to ncohen:
Obviously, regularity properties - and this is very fast with such data. Then, e.g., e.g. maximum cliques, or an optimal colouring. It's downright hopeless to do without taking symmetries into account. Or Lovasz theta number...
Hmmm... Looks like you will have an awful amount of code to write
:-P
I wouldn't classify calls to GAP as "awful amount of code" :)
comment:29 Changed 9 years ago by
To construct these, you need to be able to create the corresponding forms, which are well-studied by group theory, as they lead to finite classical groups. GAP has code to create these forms; it's not completely trivial in characteristic two. You can actually just call GAP!
This is now #14631 !
Nathann
Hello!
Sry for comming back at you so late. I had some other stuff lately!
Anways, the code looks fine (read it, run it, and obviously run sage -t) I only have two remarks.