Opened 16 months ago
Last modified 3 months ago
#28539 needs_work task
Optimization for small permutation groups
Reported by: | vdelecroix | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | sage-9.3 |
Component: | combinatorics | Keywords: | |
Cc: | tscrim, chapoton, sbrandhorst | Merged in: | |
Authors: | Vincent Delecroix | Reviewers: | |
Report Upstream: | N/A | Work issues: | |
Branch: | u/vdelecroix/28539 (Commits) | Commit: | 44bd8638bebbed543ff6f3c13846893ebca17f8b |
Dependencies: | #28544, #28652, #28653 | Stopgaps: |
Description (last modified by )
This ticket proposes micro optimizations for small permutation groups. The rationale is to handle the situation where we have billions of combinatorial objects and need to run through their automorphism groups most of which are trivial or let's say have size at most 100. An even more concrete application is given by admcycles MR 14 where there is an attempt to use graph automorphisms from Sage instead of a handmade implementation. This turns out to result in a major slowdown! For example
sage: from admcycles.admcycles import Hyperell sage: %time H = Hyperell(3)
takes 13.5 s on master but with MR 14 takes 17.4 s.
The profiling points to
- the constructor
__init__
ofPermutationGroupElement
: see #28652 - the
subgroup
method ofPermutationGroupElement
- the product
p1 * p2
whenp1
is a symmetric group element andp2
is a permutation group on the same domain: see #28652 (and also the bug #28544) __iter__
forPermutationGroupElement
(that currently involves computing a strong generating scheme): see #28652 and #28653
The optimizations proposed in this ticket noticeably speed up
the Hyperell(3)
computation mentioned above: from 17.4 s with
the previous Sage implementation or 13.5 s with admcycle's
previous handmade implementation, the timing goes down to 9 s.
Change History (19)
comment:1 Changed 16 months ago by
- Branch set to u/vdelecroix/28539
- Commit set to f67ffcc1bcfcd460a6364948e0c875573f31675c
comment:2 Changed 16 months ago by
- Description modified (diff)
comment:3 Changed 16 months ago by
- Commit changed from f67ffcc1bcfcd460a6364948e0c875573f31675c to 0dbcc3383eac6497c1f7c0711e17b9e831cfeb14
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
096659c | 28539: rework constructor of PermutationGroupElement
|
2d23d92 | 28539: faster multiplication and iteration
|
d00d370 | 28539: fix some doctests
|
5888249 | 28539: mark not tested bug tracked in #28544
|
0dbcc33 | 28539: reynolds operator and Galois conjugation
|
comment:4 Changed 16 months ago by
- Cc chapoton sbrandhorst added
- Status changed from new to needs_review
comment:5 Changed 16 months ago by
- Status changed from needs_review to needs_work
hmm some py2/py3 issue I guess.
comment:6 Changed 16 months ago by
- Commit changed from 0dbcc3383eac6497c1f7c0711e17b9e831cfeb14 to 6ca3833fff437f52136279a0c6273954f093a8b1
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
2c62905 | 28539: rework constructor of PermutationGroupElement
|
55d3e8a | 28539: faster multiplication and iteration
|
b027f91 | 28539: fix some doctests
|
5d77c23 | 28539: mark not tested bug tracked in #28544
|
6ca3833 | 28539: reynolds operator and Galois conjugation
|
comment:7 Changed 16 months ago by
- Commit changed from 6ca3833fff437f52136279a0c6273954f093a8b1 to 44bd8638bebbed543ff6f3c13846893ebca17f8b
Branch pushed to git repo; I updated commit sha1. New commits:
44bd863 | 28539: fix more doctests (python2 and python3)
|
comment:8 Changed 16 months ago by
- Status changed from needs_work to needs_review
comment:9 Changed 16 months ago by
Still failing. And proliferation of #py2 and # py3 does not seem to be a good solution.
comment:10 Changed 16 months ago by
- Status changed from needs_review to needs_info
I agree with Frédéric that adding a whole bunch of # py2
and # py3
tags is not a good solution. I am assuming this comes from this change:
- return self.iteration(algorithm="SGS") + if len(self._gens) == 1: + return self._iteration_monogen() + elif self.cardinality() <= 100: + return self.iteration(algorithm="BFS") + else: + return self.iteration(algorithm="SGS")
and the BFS
option calls RecursivelyEnumeratedSet
, which has consistency problems on Python3 IIRC. So we have to solve that bigger problem first.
I have some other comments:
I don't see the point of going to cycles just to convert back here:
return grp.element_class(self.to_cycles(singletons=False), grp, check=False)
I know this was already done, but it seems useless as the PermutationGroupElement
stores things internally as a list in essentially the same way.
I would probably Cythonize from_cycles
.
Is there a reason why _set_identity
and _set_list_images
are cpdef
and not just cdef
(which is faster when being called by C code)? By being cpdef
, they also need doctests.
comment:11 Changed 16 months ago by
Thanks for the feedback. I will cut the ticket and start by optimizing the constructor. Optimizing the iterator will be postponed to another one.
comment:12 Changed 15 months ago by
- Dependencies set to #28652
- Description modified (diff)
- Type changed from enhancement to task
comment:13 Changed 15 months ago by
- Dependencies changed from #28652 to #28544, #28652, #28653
- Description modified (diff)
comment:14 follow-up: ↓ 15 Changed 15 months ago by
See also #28674 which should eventually solve the consistency problems of RecursivelyEnumeratedSet
.
comment:15 in reply to: ↑ 14 Changed 15 months ago by
Replying to gh-mwageringel:
See also #28674 which should eventually solve the consistency problems of
RecursivelyEnumeratedSet
.
I don't think that the enumeration order is relevant here. This is convenient for doctests and only shows the weakness of them.
comment:16 Changed 13 months ago by
- Milestone changed from sage-9.0 to sage-9.1
Ticket retargeted after milestone closed
comment:17 Changed 9 months ago by
- Milestone changed from sage-9.1 to sage-9.2
Batch modifying tickets that will likely not be ready for 9.1, based on a review of the ticket title, branch/review status, and last modification date.
comment:18 Changed 5 months ago by
- Description modified (diff)
- Status changed from needs_info to needs_work
Supporting Python 2 is no longer needed now.
comment:19 Changed 3 months ago by
- Milestone changed from sage-9.2 to sage-9.3
New commits:
WIP: make small perm group faster