Opened 10 months ago
Closed 6 months ago
#25477 closed enhancement (fixed)
possibly improve the iterator for PermutationGroups
Reported by:  moritz  Owned by:  

Priority:  major  Milestone:  sage8.4 
Component:  group theory  Keywords:  PermutationGroup, days93.51, gap, days94 
Cc:  stumpc5, tscrim, vdelecroix, dimpase, rbeezer  Merged in:  
Authors:  Moritz Firsching, Christian Stump  Reviewers:  Christian Stump, Dima Pasechnik, Travis Scrimshaw 
Report Upstream:  N/A  Work issues:  
Branch:  3ec5057 (Commits)  Commit:  3ec5057ee13ac5450b3b7a2ddba09c2c4aa772c7 
Dependencies:  #25608 #26045  Stopgaps: 
Description
Currently, the iterator looks like this.
def __iter__(self): from sage.sets.recursively_enumerated_set import RecursivelyEnumeratedSet return iter(RecursivelyEnumeratedSet(seeds=[self.one()], successors=lambda g: (g._mul_(h) for h in self.gens())))
Perhaps it would be faster to use a strong_generating_system to iterate through the group.
Change History (190)
comment:1 Changed 10 months ago by
 Branch set to u/moritz/enumerate_PermutationGroup
comment:2 Changed 10 months ago by
 Commit set to 74488fe1548ff39225a13540fd98ffb3c227fe9b
comment:3 Changed 10 months ago by
More timings:
sage: P = CoxeterGroup(["E",7], implementation="permutation") sage: time len(list(P.iteration(algorithm="depth", tracking_words=False))) CPU times: user 4.55 s, sys: 525 ms, total: 5.07 s Wall time: 5.14 s 2903040 sage: time len(list(P.__iter__())) CPU times: user 21.2 s, sys: 693 ms, total: 21.8 s Wall time: 21.8 s 2903040 sage: time len(list(P.__iter_alt__())) CPU times: user 4.33 s, sys: 231 ms, total: 4.56 s Wall time: 4.58 s 2903040
comment:4 followup: ↓ 6 Changed 10 months ago by
 Type changed from PLEASE CHANGE to enhancement
You can probably get some more speed by doing the initial step in the __iter__
function and then do the remaining steps with SGS
being explicitly given. It is probably faster to also do
S = SGS.pop() if not SGS: for g in S: yield g else: for s in elements(self, SGS): for g in S: yield s._mul_(g)
comment:5 Changed 10 months ago by
 Commit changed from 74488fe1548ff39225a13540fd98ffb3c227fe9b to 3594002f0dfc1c6223efd316ffb348c8ed6446e7
Branch pushed to git repo; I updated commit sha1. New commits:
3594002  directly yield in the last step

comment:6 in reply to: ↑ 4 Changed 10 months ago by
Replying to tscrim:
You can probably get some more speed by doing the initial step in the
__iter__
function and then do the remaining steps withSGS
being explicitly given.
I don't quite follow. We would still have to compute SGS in this case, won't we? This seems to be the slow part, at least in the first example above with 60000 elements.
It is probably faster to also do ...
That makes it a little faster, thanks!
comment:7 Changed 10 months ago by
 Commit changed from 3594002f0dfc1c6223efd316ffb348c8ed6446e7 to 3dc482208fd92d5d430bcd12dcaab68971216609
Branch pushed to git repo; I updated commit sha1. New commits:
3dc4822  removing the if from the loop

comment:8 followup: ↓ 11 Changed 10 months ago by
+ def elements(self, SGS=None): + S = SGS.pop()
seems weird. I assume that you want to remove the =None
?
comment:9 Changed 10 months ago by
 Branch changed from u/moritz/enumerate_PermutationGroup to u/stumpc5/enumerate_PermutationGroup
comment:10 Changed 10 months ago by
 Branch changed from u/stumpc5/enumerate_PermutationGroup to u/moritz/enumerate_PermutationGroup
comment:11 in reply to: ↑ 8 Changed 10 months ago by
 Commit changed from 3dc482208fd92d5d430bcd12dcaab68971216609 to 7780abcd25706bb54a6a4cf3e58380bb0d57c12d
comment:12 Changed 10 months ago by
I did some more, could you also merge that change in to the branch?
comment:13 Changed 10 months ago by
 Commit changed from 7780abcd25706bb54a6a4cf3e58380bb0d57c12d to 7d3d68f7b88a7d3ab74524bdbeb1c1cf66cf9e5c
comment:14 followup: ↓ 18 Changed 10 months ago by
In def elements(self, SGS):
the argument self
is never used and you can remove it.
comment:15 Changed 10 months ago by
sage: time len(list(A.__iter_alt__())) CPU times: user 3.39 s, sys: 690 ms, total: 4.08 s Wall time: 4.1 s 60000
This computation takes much less time in gap
directly, I thus expect that doing
SGS = self.strong_generating_system(base)
directly in gap rather than in sage would improve the iteration in this case drastically. (I just tried for a bit but failed. The code in gap directly is
############################################################################# ## #F ElementsStabChain(<S>) ## InstallGlobalFunction(ElementsStabChain,function ( S ) local elms, # element list, result stb, # elements of the stabilizer pnt, # point in the orbit of <S> rep; # inverse representative for that point # if <S> is trivial then it is easy if Length(S.generators) = 0 then elms := [ S.identity ]; # otherwise else # start with the empty list elms := []; # compute the elements of the stabilizer stb := ElementsStabChain( S.stabilizer ); # loop over all points in the orbit for pnt in S.orbit do # add the corresponding coset to the set of elements rep := S.identity; while S.orbit[1] ^ rep <> pnt do rep := LeftQuotient( S.transversal[pnt/rep], rep ); od; UniteSet( elms, stb * rep ); od; fi; # return the result return elms; end);
comment:16 Changed 10 months ago by
 Reviewers set to Christian Stump
 Status changed from new to needs_info
comment:17 Changed 10 months ago by
 Branch changed from u/moritz/enumerate_PermutationGroup to u/stumpc5/enumerate_PermutationGroup
comment:18 in reply to: ↑ 14 Changed 10 months ago by
 Commit changed from 7d3d68f7b88a7d3ab74524bdbeb1c1cf66cf9e5c to 285524e6bc6d5bfee42b8d1a594fadb58b0effd7
Replying to vdelecroix:
In
def elements(self, SGS):
the argumentself
is never used and you can remove it.
done.
I also made some tests and think that the permutation group method strong_generating_system
is much slower than necessary (see the above example where this algo is slower than the brute force). In particular, there is a lot of talking back and forth between sage and gap. Anyway, for my purposes, this is a nonissue. @Dima, do you know how to easily make this method fast?
New commits:
285524e  removed self from elements arguments

comment:20 Changed 10 months ago by
posted question and code at https://groups.google.com/d/topic/sagedevel/wivuFBq7n7k/discussion.
comment:21 Changed 10 months ago by
def SGS_old(G): # taken from strong_generating_system sgs = [] stab = G base = G.base() for j in base: sgs.append(stab.transversals(j)) stab = stab.stabilizer(j) return sgs def SGS_new(G, gap_output=True): S = G._gap_().StabChain() gap.execute(gap_cosets) cosets = S.CosetsStabChain() if gap_output: return cosets # < elt_class = G._element_class() gap2sage = lambda elt: elt_class(elt, G, check=False) return [ [ gap2sage(elt) for elt in coset] # < for coset in cosets ] # < gap_cosets = """CosetsStabChain := function ( S ) local cosets, # element list, result new_coset, # pnt, # point in the orbit of <S> rep; # inverse representative for that point # if <S> is trivial then it is easy if Length(S.generators) = 0 then cosets := [ [S.identity] ]; # otherwise else # compute the elements of the stabilizer cosets := CosetsStabChain( S.stabilizer ); # loop over all points in the orbit new_coset := []; for pnt in S.orbit do # add the corresponding coset to the set of elements rep := S.identity; while S.orbit[1] ^ rep <> pnt do rep := LeftQuotient( S.transversal[pnt/rep], rep ); od; Add( new_coset, rep ); od; Add( cosets, new_coset ); fi; # return the result return cosets; end; """
comment:22 Changed 10 months ago by
The new method is much faster than the old, but then slowed down by casting the output to sage:
sage: sage: p = [(i,i+1) for i in range(1,601,2)] ....: sage: q = [tuple(range(1+i,601,3)) for i in range(3)] ....: sage: A = PermutationGroup([p,q]) sage: %time XX = SGS_old(A) CPU times: user 3.67 s, sys: 664 ms, total: 4.34 s Wall time: 4.45 s sage: %time XX = SGS_new(A, True) CPU times: user 4.94 ms, sys: 712 µs, total: 5.65 ms Wall time: 14 ms sage: %time XX = SGS_new(A, False) CPU times: user 2.48 s, sys: 116 ms, total: 2.59 s Wall time: 2.61 s
comment:23 followup: ↓ 28 Changed 10 months ago by
You should be using libgap
and not gap
. The communication would be much faster.
comment:24 Changed 10 months ago by
And why not using StrongGeneratorsStabChain
that is builtin in GAP?
comment:25 Changed 10 months ago by
You should be using libgap and not gap
Could you provide a code snippet in the above example of how to do that?
And why not using StrongGeneratorsStabChain? that is builtin in GAP?
Because this provides a list of strong generators for the stabilizer chain, but not a list of coset reprs:
gap> P := Group([(1,2),(1,2,3,4)]); Group([ (1,2), (1,2,3,4) ]) gap> S := StabChain(P); <stabilizer chain record, Base [ 1, 2, 3 ], Orbit length 4, Size: 24> gap> CosetsStabChain(S); [ [ () ], [ (), (3,4) ], [ (), (2,4,3), (2,3,4) ], [ (), (1,4)(2,3), (1,2)(3,4), (1,3)(2,4) ] ] gap> StrongGeneratorsStabChain(S); [ (3,4), (2,3,4), (1,2)(3,4), (1,4)(2,3) ]
comment:26 Changed 10 months ago by
And why not using...
Let me add that the gap code above is simply taken from the ElementsStabChain
code from gap (see PageSource(ElementsStabChain)
) and returning the cosets rather than the elements. If there was a builtin function that does this, I would be surprised if it is not used there (though it might be possible for speed reasons).
comment:27 Changed 10 months ago by
Historically, little attention was paid to the problem at hand, and indeed, iteration over all the elements of a group G, rather than doing something more intelligent, is almost surely an indication of something done without enough thought.
E.g.,
 would knowing the coset representatives of a subgroup H<G and generators for H suffice?
 would knowing the words in generators rather than permutations suffice?
 can an adavntage be taken of a short base for G?
comment:28 in reply to: ↑ 23 Changed 10 months ago by
Replying to vdelecroix:
You should be using
libgap
and notgap
. The communication would be much faster.
Yeah, if the iterator at hand uses (pexpect) GAP, merely converting it to libGAP would be quite a speedup, I suppose.
comment:29 Changed 10 months ago by
Well, let me wrap up the discussion so for:
 Moritz implemented an iteration using a short base and a stabilizer chain which are both implemented in gap (using the SchreierSims algorithm), see the attached branch. This already speeded the iteration in most situations drastically.
 Permutation group elements are faster multiplied in sage than in gap, so we want to do it there.
 The remaining bottleneck is the computation of the strong generating system for which I provided code in gap. This is now also really fast, except for the translation of the gap permutations to sage. I still need help to get this last issue disappear.
comment:30 Changed 10 months ago by
GAP has a function Elements()
which enumerates the elements of a group, did you try it directly? Probably you're reinventing the wheel...
I cannot believe that permutation multiplication in (lib)GAP is slower than in Sage. You are probably doing lots of slow conversions between Sage and pexpect GAP.
comment:31 Changed 10 months ago by
Before comparing any of these functions, we should have a way to fast translate gap permutations to sage permutations. Otherwise, this would even much more so spoil the use of the gap function Elements
which then results in all permutations to be translated from gap to sage.
Here are some preliminary timings for the Coxeter group of type E7
:
In gap, the iteration needs 9.2 secs:
gap> P := Group([(1,64)(3,12)(8,19)(15,23)(16,20)(21,26)(25,30)(27,33)(29,35)(31,34)(32,40)(36,41)(37,44)(38,43)(45,47)(49,52)(62,63)(66,75)(71,82)(78,86)(79,83)(84,89)(88,93)(90,96)(92,98)(94,97)(95,103)(99,104)(100,107)(101,106)(108,110)(112,115)(125,126), (2,65)(4,9)(8,15)(13,18)(14,24)(16,21)(19,23)(20,26)(22,28)(25,31)(27,36)(30,34)(33,41)(50,55)(54,56)(57,59)(58,60)(67,72)(71,78)(76,81)(77,87)(79,84)(82,86)(83,89)(85,91)(88,94)(90,99)(93,97)(96,104)(113,118)(117,119)(120,122)(121,123), (1,12)(3,66)(4,8)(9,15)(13,16)(14,25)(18,21)(22,27)(24,31)(28,36)(35,39)(40,42)(43,46)(44,48)(47,51)(52,53)(61,62)(64,75)(67,71)(72,78)(76,79)(77,88)(81,84)(85,90)(87,94)(91,99)(98,102)(103,105)(106,109)(107,111)(110,114)(115,116)(124,125), (2,9)(3,8)(4,67)(5,13)(11,14)(12,19)(17,22)(21,29)(26,35)(31,32)(34,40)(36,38)(41,43)(48,50)(51,54)(53,57)(60,61)(65,72)(66,71)(68,76)(74,77)(75,82)(80,85)(84,92)(89,98)(94,95)(97,103)(99,101)(104,106)(111,113)(114,117)(116,120)(123,124), (4,13)(5,68)(6,11)(8,16)(9,18)(10,17)(15,21)(19,20)(23,26)(32,37)(38,45)(40,44)(42,48)(43,47)(46,51)(57,58)(59,60)(67,76)(69,74)(71,79)(72,81)(73,80)(78,84)(82,83)(86,89)(95,100)(101,108)(103,107)(105,111)(106,110)(109,114)(120,121)(122,123), (5,11)(6,69)(7,10)(13,14)(16,25)(18,24)(20,30)(21,31)(26,34)(29,32)(35,40)(39,42)(45,49)(47,52)(51,53)(54,57)(56,59)(68,74)(70,73)(76,77)(79,88)(81,87)(83,93)(84,94)(89,97)(92,95)(98,103)(102,105)(108,112)(110,115)(114,116)(117,120)(119,122), (6,10)(7,70)(11,17)(14,22)(24,28)(25,27)(30,33)(31,36)(32,38)(34,41)(37,45)(40,43)(42,46)(44,47)(48,51)(50,54)(55,56)(69,73)(74,80)(77,85)(87,91)(88,90)(93,96)(94,99)(95,101)(97,104)(100,108)(103,106)(105,109)(107,110)(111,114)(113,117)(118,119)]); <permutation group with 7 generators> gap> Length(Elements(P)); time; 2903040 9255
while in sage, it only takes 4.3 secs of which 0.7 secs are spend constructing the strong generating system:
sage: P = CoxeterGroup(["E",7], implementation="permutation") sage: %time X = P.strong_generating_system(P.base()) CPU times: user 632 ms, sys: 71.6 ms, total: 703 ms Wall time: 718 ms sage: P = CoxeterGroup(["E",7], implementation="permutation") sage: %time len(list(P.__iter_alt__())) CPU times: user 4.11 s, sys: 208 ms, total: 4.32 s Wall time: 4.34 s 2903040
So I expect this to go down below 4 sec if we speed the strong generating system.
comment:32 Changed 10 months ago by
Do you know that GAP actually has iterators? With P as in comment 31:
gap> si:=IteratorStabChain(StabChain(P)); <iterator> gap> l:=[];; gap> for i in si do Add(l,i); od; gap> Length(l);
is about 30% faster than Elements(P)
 the latter actually will also sort the elements, perhaps that's why.
Moreover, in for i
loop about 60% of time is taken by Add()
.
(I measured this by replacing Add()
by a counter increment).
comment:33 followup: ↓ 52 Changed 10 months ago by
Oh, I forgot that Elements
sorts the output, thanks for the reminder and for improving the timing comparisons:
gap> si:=IteratorStabChain(StabChain(P));; time; 4 gap> i:=0;; gap> for j in si do i:=i+1; od; time; 2608 gap> i; 2903040
vs.
sage: i = 0 sage: %time for _ in P.__iter_alt__(): i+=1 CPU times: user 1.97 s, sys: 80.2 ms, total: 2.05 s Wall time: 2.08 s sage: i 2903040
(Is this now the timing you think is optimal in gap?) If this is the case, sage is still faster, and, again, 0.7secs are overhead that can be remomved from the sage timing, pushing it to roughly 1.5secs.
comment:34 Changed 10 months ago by
I wonder whether the SGSs in these tests use the same base.
I must say that I also don't understand the recursive code in the branch on the ticket. I suspect it won't work correctly if SGS's elements are not involutions. (E.g. if the group is cyclic, then there should be a loop over the powers of the only generator in SGS, no?)
comment:35 Changed 10 months ago by
The algorithm in sage now is the very same as the one in gap, there is no structural difference. For a general description, see for example https://math.stackexchange.com/a/1706006/234820.
In particular, both use the same base and the same stabilizer chain.
I suspect it won't work correctly if SGS's elements are not involutions.
This is not correct if I understand it correctly. In particular, the elements in the SGS are usually not only involutions, for example
sage: S = PermutationGroup([(1,2),(1,2,3)]) sage: S.strong_generating_system() [[(), (1,2,3), (1,3,2)], [(), (2,3)], [()]]
and the SGS is not a generating set for the group itself. Another example of a cyclic group is
sage: P = PermutationGroup([(1,2,3,4)]) sage: for elt in P.__iter_alt__(): print elt () (1,4,3,2) (1,3)(2,4) (1,2,3,4)
and the stabilizer chain is trivial (i.e., the chain of cosets is a single coset of the trivial subgroup).
comment:36 Changed 10 months ago by
ok, so these are for g in S
loops that iterate over subgroups S, right?
What iterator is there? Do you want to use your iterator there, explicitly?
comment:37 followup: ↓ 38 Changed 10 months ago by
Sorry, I am slightly lost now in what you are asking  let me try to answer anyway.
Let S be a permutation group in sage. The current iterator for g in S
iterates by a brute force algorithm through the elements keeping the complete group in memory to check if an element was seen before.
The new algorithm reimplements the algorithm used in gap, and indeed takes the important ingredients from gap. gap computes a chain e = S1 in S2 in ... in Sk = S
of subgroups (obtained using the SchreierSims algorithm) for which the cosets of Si
inside S{i+1}
are particularly easy to compute.
This yields a sequence of cosets [e]=C1, C2, ..., Ck
such that every element in S
has a unique representation g = g1*...*gk
for gi in Ci
.
In sage, the new algorithm is to
 directly compute in gap the list
C1, C2, ..., Ck
 translate the elements in all these lists to sage (this takes too long and should be improved)
 produce an iterator for all elements in
S
by iterating over all products of elements in these lists.
Let me know if you meant something else...
comment:38 in reply to: ↑ 37 Changed 10 months ago by
Replying to stumpc5:
Let me know if you meant something else...
I meant
lines 844 and 848
in your patch, both say for g in S:
 how do these iterations work? (I imagine S
is a subgroup in the SGS chain).
comment:39 Changed 10 months ago by
in your patch, both say for g in S:  how do these iterations work? (I imagine S is a subgroup in the SGS chain)
No, S = SGS.pop()
so S = Ci
is the next layer of coset representatives. Let us go through the code with the notation as above:
def elements(SGS): S = SGS.pop() if not SGS: for g in S: yield g else: for s in elements(SGS): for g in S: yield s._mul_(g)
Given such a sequence SGS = C1,C2,...,Ci
, elements(SGS)
iterates over all elements in Si
. This is done by recursively doing the computation for C1,C2,..,C{i1}
and then yielding all elements in S{i1}
multiplied with all elements in S=Ci
.
if not SGS
means that we have reached the trivial subgroup and S = [()]
. So the first for g in S: yield g
could be replaced with yield S[0]
.
comment:40 Changed 10 months ago by
Well, by right, SGS is a generating set. So your naming scheme (no other documentation :)) is misleading...
comment:41 Changed 10 months ago by
SGS is a strong generating system taken from the sage naming scheme. The later might be misleading, though, since it is not a generating set but a sequence of coset reprs...
comment:42 Changed 10 months ago by
 Commit changed from 285524e6bc6d5bfee42b8d1a594fadb58b0effd7 to 8f70da5d918f87c50383bbb368f1c92eb5b5aee4
Branch pushed to git repo; I updated commit sha1. New commits:
8f70da5  speeded strong_generating_system

comment:43 Changed 10 months ago by
with the new commit, the timings from the beginning become
sage: p = [(i,i+1) for i in range(1,601,2)] ....: q = [tuple(range(1+i,601,3)) for i in range(3)] ....: A = PermutationGroup([p,q]) ....: A.cardinality() ....: 60000 sage: time len(list(A)) CPU times: user 458 ms, sys: 56.2 ms, total: 514 ms Wall time: 512 ms 60000 sage: time len(list(A.__iter_alt__())) CPU times: user 2.97 s, sys: 167 ms, total: 3.13 s Wall time: 3.23 s 60000 sage: time x = A.strong_generating_system(A.base()) CPU times: user 4.51 s, sys: 396 ms, total: 4.9 s Wall time: 5.08 s sage: time x = A.strong_generating_system(implementation="gap") CPU times: user 2.67 s, sys: 80.3 ms, total: 2.75 s Wall time: 2.77 s
so the iterations are equally fast, but the translation from gap permutations to sage permutations takes 2.5 secs.
comment:44 Changed 10 months ago by
Do you have a problem using libGAP rather than GAP?
comment:45 followup: ↓ 46 Changed 10 months ago by
You should be using libgap and not gap
Could you provide a code snippet in the above example of how to do that?
No, I just do now know how to do it, see my above comment from comment:25 .
comment:46 in reply to: ↑ 45 Changed 10 months ago by
Replying to stumpc5:
You should be using libgap and not gap
Could you provide a code snippet in the above example of how to do that?
No, I just do now know how to do it, see my above comment from comment:25 .
You can have a look at CossidentePenttilaGraph() for the use of libgap.function_factory
(so that you can basically call your own GAP function via libgap).
So you can change your code as follows:
gap_cosets = libgap.function_factory("""function ( S0 ) local CosetsStabChain; CosetsStabChain := function(S) # for the recursive call local cosets, # element list, result new_coset, # pnt, # point in the orbit of <S> rep; # inverse representative for that point # if <S> is trivial then it is easy if Length(S.generators) = 0 then cosets := [ [S.identity] ]; # otherwise else # compute the elements of the stabilizer cosets := CosetsStabChain( S.stabilizer ); # loop over all points in the orbit new_coset := []; for pnt in S.orbit do # add the corresponding coset to the set of elements rep := S.identity; while S.orbit[1] ^ rep <> pnt do rep := LeftQuotient( S.transversal[pnt/rep], rep ); od; Add( new_coset, rep ); od; Add( cosets, new_coset ); fi; # return the result return cosets; end; return CosetsStabChain(S0); end;""")
Now one can do
sage: G=libgap.AlternatingGroup(4) sage: S=G.StabChain() sage: gap_cosets(S) [ [ () ], [ (), (2,4,3), (2,3,4) ], [ (), (1,4,3), (1,3,4), (1,2,4) ] ]
another useful thing is syntax like G=libgap(PermutationGroup([(1,2)]))
to convert
from Sage's group (implemented with pexpect GAP, I gather) to libgap.
comment:47 Changed 10 months ago by
Thank you, Dima! I did these changes together with tons of small changes that had a huge impact on the running time.
Beside this, I arrived at the following, and wonder if this is okay doing: Given I have
 a
PermutationGroupElement
"sample" and  a
list
"new_perm" representing a permutation in oneline notation in the *same permutation group* as "sample"
It seems that, oddly, we do not have a fast way of generating new permutations from these lists, despite the fact that we can multiply permutations very fast. I thus provide a new PermutationGroupElement
method _generate_new
that basically takes a copy from the given PermutationGroupElement
and only overwrites its underlying c list. The code is basically copied from _mul_
.
An example would be
sage: S = PermutationGroup(SymmetricGroup(4).gens()) sage: sample = S([2,3,4,1]) sage: lst1 = [] sage: lst2 = [2,1] sage: lst3 = [4,3,2,1] sage: pi1 = sample._generate_new(lst1); pi1 () sage: pi2 = sample._generate_new(lst2); pi2 (1,2) sage: pi3 = sample._generate_new(lst3); pi3 (1,4)(2,3)
comment:48 Changed 10 months ago by
 Commit changed from 8f70da5d918f87c50383bbb368f1c92eb5b5aee4 to f5a48ddbd2134dbeb94fcfb0c8923bdf7edf1d2a
Branch pushed to git repo; I updated commit sha1. New commits:
f5a48dd  new permutation group element method _generate_new, improved speed for strong generating system

comment:49 Changed 10 months ago by
And here is the new timings:
sage: sage: p = [(i,i+1) for i in range(1,601,2)] ....: ....: q = [tuple(range(1+i,601,3)) for i in range(3)] ....: ....: A = PermutationGroup([p,q]) ....: ....: A.cardinality() ....: 60000 sage: sage: time len(list(A)) CPU times: user 514 ms, sys: 52.2 ms, total: 566 ms Wall time: 535 ms 60000 sage: sage: time len(list(A.__iter_alt__())) CPU times: user 588 ms, sys: 91 ms, total: 679 ms Wall time: 669 ms 60000 sage: sage: time len(list(A)) CPU times: user 469 ms, sys: 72.5 ms, total: 542 ms Wall time: 529 ms 60000 sage: sage: time len(list(A.__iter_alt__())) CPU times: user 375 ms, sys: 52.3 ms, total: 427 ms Wall time: 419 ms 60000 sage: sage: time x = A.strong_generating_system(A.base()) CPU times: user 3.82 s, sys: 784 ms, total: 4.6 s Wall time: 4.69 s sage: sage: time x = A.strong_generating_system(implementation="gap") CPU times: user 281 ms, sys: 127 µs, total: 281 ms Wall time: 280 ms
comment:50 Changed 10 months ago by
 Commit changed from f5a48ddbd2134dbeb94fcfb0c8923bdf7edf1d2a to 762d3188f87187f6f1d40b49729908a858e61461
Branch pushed to git repo; I updated commit sha1. New commits:
762d318  added doc for _generate_new

comment:51 Changed 10 months ago by
 Status changed from needs_info to needs_review
I set this to "needs review" for a technical review of the code where I still hope for input for improvements (which will not only be relevant for my particular purpose!).
Once this is settled, I propose to use the now PermutationGroup
iterator per default (and I would also be interested in examples where the old iterator is still faster).
comment:52 in reply to: ↑ 33 Changed 10 months ago by
Comparing the gap and the sage iterators from comment:33, we now have:
gap> si:=IteratorStabChain(StabChain(P)); <iterator> gap> i:=0;; gap> for j in si do i:=i+1; od; time; 2523 gap> i; 2903040
vs.
sage: sage: i = 0 ....: sage: %time for _ in P.__iter_alt__(): i+=1 ....: CPU times: user 1.49 s, sys: 28.2 ms, total: 1.52 s Wall time: 1.59 s sage: i 2903040
comment:53 Changed 10 months ago by
The right thing to do (not on this ticket, I guess it's a nontrivial amount of work) is to convert the whole sage/groups/perm_gps
to libGAP.
This ticket shows that the performance improvements are big.
comment:54 Changed 10 months ago by
This ticket shows that the performance improvements are big
Let me remark that the biggest performance boost came from generating new permutation group elements from old using the new _generate_new
method. The use of libGAP also played a role, though.
comment:55 Changed 10 months ago by
1) Regarding the timing (GAP iterator vs your iterator). Am I right that they both operate with (lib)GAP data? (i.e. that mul call on permutations in __iter_alt__
, is it actually in (lib)GAP?)
2) I don't understand the hack one._generate_new(libgap.ListPerm?(elt).sage()). I thought that libgap has a fast method to convert GAP permutations to Sage. E.g.
sage: G=libgap.AlternatingGroup(4) sage: gg=G.GeneratorsOfGroup() sage: gg.sage() [(1,2,3), (2,3,4)] sage: type(g.sage()[0]) <type 'sage.groups.perm_gps.permgroup_element.PermutationGroupElement'> sage: type(g[0]) <type 'sage.libs.gap.element.GapElement_Permutation'>
comment:56 followup: ↓ 57 Changed 10 months ago by
i.e. that mul call on permutations in iter_alt, is it actually in (lib)GAP?
No, this is pure cython and uses PermutationGroupElement._mul_(left, _right)
, no (lib)GAP involved here.
Since both algorithms are the same, and the strong generating set in the Sage version is taken through libGAP, I suspect that the time advantage of Sage really comes from this superfast cython multiplication of permutation group elements.
I thought that libgap has a fast method to convert GAP permutations to Sage
This is not the case: libgap uses GapElement_Permutation.sage
which returns PermutationGroupElement(libgap.ListPerm(self).sage())
, so it goes through the ordinary permutation group element constructor that is very slow because of tons of checks. This is why I wrote _generate_new
that just uses the data from a given element and overwrites its c array containing the permutation:
sage: P = PermutationGroup([(1,2),(1,2,3,4)]) sage: one = P.one() sage: l = [4,3,2,1] sage: %timeit P(l) 1000 loops, best of 3: 579 µs per loop sage: %timeit one._generate_new(l) The slowest run took 39.93 times longer than the fastest. This could mean that an intermediate result is being cached. 1000000 loops, best of 3: 203 ns per loop
comment:57 in reply to: ↑ 56 Changed 10 months ago by
Replying to stumpc5:
I thought that libgap has a fast method to convert GAP permutations to Sage
This is not the case: libgap uses
GapElement_Permutation.sage
which returnsPermutationGroupElement(libgap.ListPerm(self).sage())
, so it goes through the ordinary permutation group element constructor that is very slow because of tons of checks. This is why I wrote_generate_new
that just uses the data from a given element and overwrites its c array containing the permutation:
Shouldn't then this be used to improve the code in src/sage/libs/gap/?
Cause that's what it does, you provide a better implementation for <libgap perm>.sage()
, right?
comment:58 Changed 10 months ago by
Not really, because my method (A) makes use of the fact that one knows the permutation group the element lives in a priori, and (B) does not check the input whatsoever for correctness (and might result in segfaults if not used properly).
The first is an issue because <libgap perm>
does not know which parent a gap permutation lives in (and neither does gap iirc), while the second might be neglected in case we expect that we always get something reasonable fromo gap.
comment:59 Changed 10 months ago by
OK, I see. Still, libgap should be using the lowlevel C array with GAP permutation data, rather than converting GAP list > Sage list > PermutationGroupElement? (creating, if needed, a parent permutation group along the way, no?)
I don't understand whether this involves calling pexpect GAP or not.
comment:60 followup: ↓ 61 Changed 10 months ago by
I don't understand whether this involves calling pexpect GAP or not.
What involved pexpect GAP? This creation of a PermutationGroupElement
? Then the answer is no, there is no gap object attached by default to a PermutationGroupElement
.
comment:61 in reply to: ↑ 60 Changed 10 months ago by
Replying to stumpc5:
I don't understand whether this involves calling pexpect GAP or not.
What involved pexpect GAP? This creation of a
PermutationGroupElement
? Then the answer is no, there is no gap object attached by default to aPermutationGroupElement
.
OK, thanks  it's not immediately clear with all that methods using _gap_
in that class.
Anyhow, I don't understand why libGAP creates PermutationGroupElement
rather than
a Permutation
.
It would be natural to me to have this as the default,
mostly as it does not involve constructing a parent (GAP permutations don't really have parents in GAP, they are all in every SymmetricGroup()
of degree at least LargestMovedPoint()
of the permutation.
Then your hack can be used for fast libgap>Sage conversion of permutations.
comment:62 Changed 10 months ago by
It would be natural to me to have this as the default
I agree, this would get down the speed quite a bit
sage: P = PermutationGroup([(1,2),(1,2,3,4,5,6,7,8)]) sage: l = [8,7,6,5,4,3,2,1] sage: %timeit P(l, check=False) The slowest run took 7.58 times longer than the fastest. This could mean that an intermediate result is being cached. 10000 loops, best of 3: 44.3 µs per loop sage: %timeit Permutation(l, check_input=False) The slowest run took 7.85 times longer than the fastest. This could mean that an intermediate result is being cached. 100000 loops, best of 3: 6.74 µs per loop
but my hack would not work in this case because it uses the c structure underlying PermutationGroupElement
which doesn't exist (caution: haven't rechecked!) for Permutation
, and this hack is possibly still an order of magnitude faster
sage: one = P.one() sage: %timeit one._generate_new(l) The slowest run took 128.70 times longer than the fastest. This could mean that an intermediate result is being cached. 1000000 loops, best of 3: 241 ns per loop
comment:63 Changed 9 months ago by
 Commit changed from 762d3188f87187f6f1d40b49729908a858e61461 to 952b29227535c6cf15979bcb8d7c1baea065f43a
comment:64 Changed 9 months ago by
Okay, now everything is as fast as I was expecting it to be possible! I now do not create a sage list from the libgap list and then fill a <int*>
with this data, but create the latter directly from the libgap list entries. This removes all the overhead!
Here are the new timings:
sage: p = [(i,i+1) for i in range(1,601,2)] ....: q = [tuple(range(1+i,601,3)) for i in range(3)] ....: A = PermutationGroup([p,q]) ....: A.cardinality() ....: 60000 sage: i=0 sage: %time for _ in A.__iter__(): i+=1 CPU times: user 512 ms, sys: 40.3 ms, total: 552 ms Wall time: 543 ms sage: i 60000 sage: i=0 sage: %time for _ in A.__iter_alt__(): i+=1 CPU times: user 132 ms, sys: 23.7 ms, total: 156 ms Wall time: 137 ms sage: i 60000 sage: %time X = A.strong_generating_system(A.base()) CPU times: user 3.5 s, sys: 675 ms, total: 4.17 s Wall time: 4.22 s sage: [ len(x) for x in X ] [600, 100] sage: %time Y = A.strong_generating_system(implementation="gap") CPU times: user 38.3 ms, sys: 129 µs, total: 38.5 ms Wall time: 38.2 ms sage: [ len(y) for y in Y ] [1, 100, 600]
comment:65 followups: ↓ 69 ↓ 74 Changed 9 months ago by
 Status changed from needs_review to needs_info
I consider it wrong to define (as I did) the method _generate_perm(self, old)
for libGAP_List
(handing over a PermutationGroupElement old
. I think it should rather exist a method _generate_new_libgap(self, gaplst
for PermutationGroupElement
that takes as input a libGAP_List gaplst
.
I was not able to do that due to import errors and my ignorance how to properly cast the objects into the correct types, but this seems only a matter of proper coding in cython
. @Travis or @Dima, could you help with this?
I think once this is settled, the code is ready for review!
@Moritz: rather incredible speedup compared to your original call of strong_generating_system
, hm?
comment:66 Changed 9 months ago by
 Commit changed from 952b29227535c6cf15979bcb8d7c1baea065f43a to d49798c44257f9959abe27b632f22ce1f872ff5b
Branch pushed to git repo; I updated commit sha1. New commits:
d49798c  removed todo

comment:67 Changed 9 months ago by
 Commit changed from d49798c44257f9959abe27b632f22ce1f872ff5b to 2be32afc29cf43fe798fd5d12cba00f546f401b4
Branch pushed to git repo; I updated commit sha1. New commits:
2be32af  removed todo

comment:68 followup: ↓ 71 Changed 9 months ago by
I can probably try it late tomorrow or the day after (I promised Darij I would review #25326 first). So Dima, let me know if you are going to work on this tomorrow.
comment:69 in reply to: ↑ 65 Changed 9 months ago by
Replying to stumpc5:
@Moritz: rather incredible speedup compared to your original call of
strong_generating_system
, hm?
Yes, absolutely great! As I see it, the new __iter_alt_
method is now faster then __iter__
in all cases, right? Therefore I propose to replace __iter__
with the __iter_alt__
before puuting this ticket on review.
comment:70 Changed 9 months ago by
No, not quite. The new __iter_alt__
is still slower for small groups (size ~ <500 elts). I still propose to use ___iter_alt__
per default, but leave the option to use the brute force iteration if desired (in case you want to loop through many small groups.
The issue is that if the group is really small, waiting even for a tiny information from libgap
is slower than exploring the group directly.
comment:71 in reply to: ↑ 68 Changed 9 months ago by
Replying to tscrim:
I can probably try it late tomorrow or the day after (I promised Darij I would review #25326 first). So Dima, let me know if you are going to work on this tomorrow.
I suggest that the documentation says that libGAP (rather than just GAP) is used. That's all for me for the time being (swamped with other things).
comment:72 Changed 9 months ago by
 Commit changed from 2be32afc29cf43fe798fd5d12cba00f546f401b4 to 448202560fde1b721f3635c438c894d023b0afca
Branch pushed to git repo; I updated commit sha1. New commits:
4482025  Merge branch 'develop' into t/25477/enumerate_PermutationGroup

comment:73 Changed 9 months ago by
What is the current state here?
comment:74 in reply to: ↑ 65 ; followup: ↓ 75 Changed 9 months ago by
Replying to stumpc5:
I consider it wrong to define (as I did) the method
_generate_perm(self, old)
forlibGAP_List
(handing over aPermutationGroupElement old
. I think it should rather exist a method_generate_new_libgap(self, gaplst
forPermutationGroupElement
that takes as input alibGAP_List gaplst
.I was not able to do that due to import errors and my ignorance how to properly cast the objects into the correct types, but this seems only a matter of proper coding in
cython
. @Travis or @Dima, could you help with this?
I am still waiting for someone to have a look at this...
In principle, I think this implementation is a strong improvement to permutation groups in Sage, and since I am not very good in optimizing in cython, there might a few simple improvements left to be found. I don't think it is ready for a positive review, but it certainly is for a review of the technical details.
comment:75 in reply to: ↑ 74 Changed 9 months ago by
Replying to stumpc5:
Replying to stumpc5:
I consider it wrong to define (as I did) the method
_generate_perm(self, old)
forlibGAP_List
(handing over aPermutationGroupElement old
. I think it should rather exist a method_generate_new_libgap(self, gaplst
forPermutationGroupElement
that takes as input alibGAP_List gaplst
.I was not able to do that due to import errors and my ignorance how to properly cast the objects into the correct types, but this seems only a matter of proper coding in
cython
. @Travis or @Dima, could you help with this?I am still waiting for someone to have a look at this...
Could you post a branch with this import problem? It'd be much quicker to see what's going on this way? (it need not become the new branch on this ticket, certainly)
comment:76 Changed 9 months ago by
 Commit changed from 448202560fde1b721f3635c438c894d023b0afca to 85a01c55af86920e4f82948a3e99bc9850558026
Branch pushed to git repo; I updated commit sha1. New commits:
85a01c5  not working attempt to move the permutation generation from libgap_list to PermutationGroupElement

comment:77 Changed 9 months ago by
Could you post a branch with this import problem? It'd be much quicker to see what's going on this way?
I had deleted that attempt, but it was basically what I just pushed. My problem was that I didn't see how to handle libGAP_INT_INTOBJ, libGAP_ELM_LIST
inside permgroup_element.pyx
.
New commits:
85a01c5  not working attempt to move the permutation generation from libgap_list to PermutationGroupElement

comment:78 Changed 9 months ago by
for starters, I think you need
+++ b/src/sage/groups/perm_gps/permgroup_element.pyx @@ 77,7 +77,7 @@ from sage.sets.finite_enumerated_set import FiniteEnumeratedSet import sage.structure.coerce as coerce from sage.structure.richcmp cimport richcmp_not_equal, rich_to_bool from sage.libs.gap.element cimport libGAP_Obj, libGAP_INT_INTOBJ, libGAP_ELM_LIST +from sage.libs.gap.gap_includes cimport libGAP_Obj, libGAP_INT_INTOBJ, libGAP_ELM_LIST import operator
after this one gets
[sagelib8.3.beta5] Error compiling Cython file: [sagelib8.3.beta5]  [sagelib8.3.beta5] ... [sagelib8.3.beta5] for i from vn <= i < old.n: [sagelib8.3.beta5] new.perm[i] = i [sagelib8.3.beta5] return new [sagelib8.3.beta5] [sagelib8.3.beta5] cpdef _generate_new_GAP(old, self): [sagelib8.3.beta5] cdef libGAP_Obj obj = self.value [sagelib8.3.beta5] ^ [sagelib8.3.beta5]  [sagelib8.3.beta5] [sagelib8.3.beta5] sage/groups/perm_gps/permgroup_element.pyx:894:34: Cannot convert Python object to 'libGAP_Obj' [sagelib8.3.beta5] Traceback (most recent call last): [sagelib8.3.beta5] File "/home/dima/sagetracmirror/local/lib/python2.7/sitepackages/Cython/Build/Dependencies.py", line 1164, in cythonize_one_helper [sagelib8.3.beta5] return cythonize_one(*m) [sagelib8.3.beta5] File "/home/dima/sagetracmirror/local/lib/python2.7/sitepackages/Cython/Build/Dependencies.py", line 1146, in cythonize_one [sagelib8.3.beta5] raise CompileError(None, pyx_file) [sagelib8.3.beta5] CompileError: sage/groups/perm_gps/permgroup_element.pyx
which hopefully makes sense to you.
comment:79 Changed 9 months ago by
 Commit changed from 85a01c55af86920e4f82948a3e99bc9850558026 to 49b68c4f8aa6925e4ea0b721760ce8ed5c762c4a
Branch pushed to git repo; I updated commit sha1. New commits:
49b68c4  here is the next import crash

comment:80 Changed 9 months ago by
okay, here is the next one that doesn't. It now compiles but crashes on startup with the following import error:
ImportError: /home/stumpc5/Programs/sage/local/lib/python2.7/sitepackages/sage/groups/perm_gps/permgroup_element.so: undefined symbol: libGAP_ElmListFuncs
comment:81 Changed 9 months ago by
You have this line:
cdef GapElement_List self = <GapElement_List> self_tmp
which does not make sense to me. Is it mean to be a C cast? Something else?
comment:82 followup: ↓ 83 Changed 9 months ago by
Yes, it is meant to be a C cast: self_tmp
(sorry for the stupid names, I would make these nicer once it works) arrives as a python object because it is a cpdef
, so to access its "C part", I needed to do this (actually without the <GapElement_List>
cast, but only the cdef GapElement_List self = self_tmp
iirc.
comment:83 in reply to: ↑ 82 Changed 9 months ago by
Replying to stumpc5:
Yes, it is meant to be a C cast:
self_tmp
(sorry for the stupid names, I would make these nicer once it works) arrives as a python object because it is acpdef
,
I would be very surprised seeing a C cast magically converting a Python object into a GAP one.
so to access its "C part", I needed to do this (actually without the
<GapElement_List>
cast, but only thecdef GapElement_List self = self_tmp
iirc.
comment:84 Changed 9 months ago by
I would be very surprised seeing a C cast magically converting a Python object into a GAP one.
Well, please see that the very same code in sage.libs.gap.element.GapElement_List._generate_perm
works, and it doesn't without the cast cdef PermutationGroupElement tmp = <PermutationGroupElement> old
. I thought this is because it arrives as a python object PermutationGroupElement
(which doesn't have access to the cython data structures) and I cast it into a cython object.
comment:85 Changed 9 months ago by
Does one really need to make it cpdef? Perhaps start with cdef, make a cpdef wrapper then?
comment:86 Changed 9 months ago by
now I am confused. The current branch works for me.
comment:87 Changed 9 months ago by
now I am confused. The current branch works for me.
compiling, or also running sage? I got the import error as in comment:80 only when running sage.
Does one really need to make it cpdef? Perhaps start with cdef, make a cpdef wrapper then?
I could try this, but it seems so simple: I have a cpdef function on class A that takes an element of class B as second argument, and I want to move this to a cpdef function on class B that takes an element of class A as second argument...
comment:88 Changed 9 months ago by
OK, more precisely, all is fine on OSX, but on Linux Sage crashes at startup, with the import error as you posted!
from the crash report:
... /home/dima/sagetracmirror/local/lib/python2.7/sitepackages/sage/groups/perm_gps/permgroup.py in <module>() 131 # Distributed under the terms of the GNU General Public License (GPL) ... 145 from sage.interfaces.gap import gap, GapElement > 146 from sage.groups.perm_gps.permgroup_element import PermutationGroupElement, standardize_generator global sage.groups.perm_gps.permgroup_element = undefined ... ImportError: /home/dima/sagetracmirror/local/lib/python2.7/sitepackages/sage/groups/perm_gps/permgroup_element.so: undefined symbol: libGAP_ElmListFuncs
comment:89 Changed 9 months ago by
And this is not a surprise:
$ ldd local/lib/python2.7/sitepackages/sage/groups/perm_gps/permgroup_element.so linuxvdso.so.1 => (0x00007fffe53f0000) libpython2.7.so.1.0 => /home/dima/sagetracmirror/local/lib/libpython2.7.so.1.0 (0x00007c9a2c87c000) libpthread.so.0 => /lib/x86_64linuxgnu/libpthread.so.0 (0x00007c9a2c65f000) libc.so.6 => /lib/x86_64linuxgnu/libc.so.6 (0x00007c9a2c295000) libdl.so.2 => /lib/x86_64linuxgnu/libdl.so.2 (0x00007c9a2c091000) libutil.so.1 => /lib/x86_64linuxgnu/libutil.so.1 (0x00007c9a2be8e000) libm.so.6 => /lib/x86_64linuxgnu/libm.so.6 (0x00007c9a2bb85000) /lib64/ldlinuxx8664.so.2 (0x00007c9a2cedf000)
it is not linked with libgap, that's why.
comment:90 Changed 9 months ago by
I have no idea what that means! (Or rather how to fix this.)
comment:91 Changed 9 months ago by
Compare this with the libgap.so extension:
$ ldd local/lib/python2.7/sitepackages/sage/libs/gap/libgap.so linuxvdso.so.1 => (0x00007ffe0d3fd000) libgap.so.4 => /home/dima/sagetracmirror/local/lib/libgap.so.4 (0x00007f4959fa5000) libpython2.7.so.1.0 => /home/dima/sagetracmirror/local/lib/libpython2.7.so.1.0 (0x00007f4959b85000) libpthread.so.0 => /lib/x86_64linuxgnu/libpthread.so.0 (0x00007f4959968000) libc.so.6 => /lib/x86_64linuxgnu/libc.so.6 (0x00007f495959e000) libm.so.6 => /lib/x86_64linuxgnu/libm.so.6 (0x00007f4959295000) libdl.so.2 => /lib/x86_64linuxgnu/libdl.so.2 (0x00007f4959091000) libutil.so.1 => /lib/x86_64linuxgnu/libutil.so.1 (0x00007f4958e8e000) /lib64/ldlinuxx8664.so.2 (0x00007f495ac26000)
you see there libgap.so.4, so it can find the symbols there...
Surely it's some declaration missing somewhere, and that's all. Or, perhaps, the corresponding GAP function should somehow be blessed in libgap extension.
comment:92 Changed 9 months ago by
Does this mean I should rather not move the method and keep the current version?
comment:93 Changed 9 months ago by
No, this just means we have to ask people who know Cython better. It must be totally trivial to fix.
I have an idea how it is done via setup.py, but here it's done in some other way, and cannot see any trace anywhere of how and why libgap.so extension gets linked to the correct dynamic library.
comment:94 Changed 9 months ago by
I've asked here: https://groups.google.com/d/msg/sagedevel/_d28OHHsnE4/WnYr1L6NCAAJ
comment:95 followup: ↓ 97 Changed 9 months ago by
here is a fix that makes it work:
$ git diff diff git a/src/sage/groups/perm_gps/permgroup_element.pxd b/src/sage/groups/perm_gps/permgroup_element.pxd index 08a928b..e261780 100644  a/src/sage/groups/perm_gps/permgroup_element.pxd +++ b/src/sage/groups/perm_gps/permgroup_element.pxd @@ 1,3 +1,4 @@ +# distutils: libraries = gap from sage.structure.element cimport MultiplicativeGroupElement, MonoidElement, Element from sage.structure.list_clone cimport ClonableIntArray
(at least with this I can start sage all right)
PS. Tests pass, too.
comment:96 Changed 9 months ago by
 Reviewers changed from Christian Stump to Christian Stump, Dima Pasechnik
comment:97 in reply to: ↑ 95 Changed 9 months ago by
Replying to dimpase:
here is a fix that makes it work:
$ git diff diff git a/src/sage/groups/perm_gps/permgroup_element.pxd b/src/sage/groups/perm_gps/permgroup_element.pxd index 08a928b..e261780 100644  a/src/sage/groups/perm_gps/permgroup_element.pxd +++ b/src/sage/groups/perm_gps/permgroup_element.pxd @@ 1,3 +1,4 @@ +# distutils: libraries = gap from sage.structure.element cimport MultiplicativeGroupElement, MonoidElement, Element from sage.structure.list_clone cimport ClonableIntArray
That fix shouldn't be needed (I created #25608 for that).
comment:98 Changed 9 months ago by
 Commit changed from 49b68c4f8aa6925e4ea0b721760ce8ed5c762c4a to 6654f752bc716676c05f37e2845c4d7c1babc1fe
Branch pushed to git repo; I updated commit sha1. New commits:
6654f75  moved things around, ready for review

comment:99 Changed 9 months ago by
 Status changed from needs_info to needs_review
Okay, the method move is now finished, setting it back to review. Still open to see (maybe @tscrim?) if there is a "simple" way to further speed _generate_new
and _generate_new_GAP
in permgroup_element
.
comment:100 Changed 9 months ago by
 Status changed from needs_review to needs_work
Adding # distutils: gap
to src/sage/groups/perm_gps/permgroup_element.pxd
is not correct since permgroup_element.pxd
has nothing to do with libGAP. Only the implementation requires libGAP, so the distutils declaration should be in the .pyx
file.
But really, you should just use #25608 instead and not add # distutils: gap
.
comment:101 Changed 9 months ago by
 Commit changed from 6654f752bc716676c05f37e2845c4d7c1babc1fe to 70fbfffa7f8a9b04dcc5a13822016f13f877dd16
Branch pushed to git repo; I updated commit sha1. New commits:
70fbfff  Merge branch 'develop' into t/25477/enumerate_PermutationGroup

comment:102 Changed 9 months ago by
 Commit changed from 70fbfffa7f8a9b04dcc5a13822016f13f877dd16 to f99aee18b8af58105d6464eee644284731660a37
comment:103 followup: ↓ 106 Changed 9 months ago by
 You should use
range()
instead of this outdated syntax:for i from 0 <= i < vn:
 Are you certain that
cdef int vn = lst.__len__()
won't overflow? As far as I know, both Python and libGAP support lists with over 2^{32} elements. Better usePy_ssize_t
, which is anyway the standard CPython type for lengths.
 Why did you write
lst.__len__()
instead oflen(lst)
?
 Why are the new methods
cpdef
instead ofdef
? They are not called from Cython, so that's only a pessimization.
 Why
cdef PermutationGroupElement tmp = <PermutationGroupElement> self
?
 This is dangerous:
<GapElement_List> lst_in
since you don't know thatlst_in
is aGapElement_List
. Either do an explicitisinstance()
check or use<GapElement_List?>lst_in
.
comment:104 Changed 9 months ago by
 Commit changed from f99aee18b8af58105d6464eee644284731660a37 to c9b495e0e22d3c0af1f22fb7c9826d2f16ad3082
Branch pushed to git repo; I updated commit sha1. New commits:
c9b495e  fixed issues raised by jdemeyer

comment:105 Changed 9 months ago by
 Commit changed from c9b495e0e22d3c0af1f22fb7c9826d2f16ad3082 to 1be187efe05a7ee899d3a715380cb636aa29c1c0
Branch pushed to git repo; I updated commit sha1. New commits:
1be187e  removed old artefact in code

comment:106 in reply to: ↑ 103 ; followup: ↓ 112 Changed 9 months ago by
Replying to jdemeyer:
 You should use
range()
instead of this outdated syntax:
done
 Are you certain that
cdef int vn = lst.__len__()
won't overflow? As far as I know, libGAP supports lists with over2^32^
elements. Better usePy_ssize_t
, which is anyway the standard CPython type for lengths.
done
 Why did you write
lst.__len__()
instead oflen(lst)
?
doesn't the second call the first? I thought that I'd rather use the first then.
 Why are the new methods
cpdef
instead ofdef
? They are not called from Cython, so that's only a pessimization.
my impression is that these are now the fastest way to create new permutations in sage, so I want to propagate their use, especially in critical cythonized places.
 Why
cdef PermutationGroupElement tmp = <PermutationGroupElement> self
?
removed
 This is dangerous:
<GapElement_List> lst_in
since you don't know thatlst_in
is aGapElement_List
. Either do an explicitisinstance()
check or use<GapElement_List?>lst_in
.
I would like to do cpdef _generate_new_GAP(self, GapElement_List lst_in)
but do not know how
New commits:
c9b495e  fixed issues raised by jdemeyer

1be187e  removed old artefact in code

comment:107 Changed 9 months ago by
I don't understand why you're moving things back and forth  don't you want to provide an optimised replacement for GapElement_Permutation
in sage.libs.gap.element
?
comment:108 Changed 9 months ago by
No, I want to obtain an optimized way to create a PermutationGroupElement
from a GapElement_Permutation
given that I have given a permutation group element of the same parent. This thus became a method for PermutationGroupElement
with argument GapElement_List
. In particular, I have this method now for python lists and for gap list.
As a byproduct, one may call this from the one
of the parent if only the parent is given but not the element.
See that this later is indeed slower:
sage: P = PermutationGroup([(1,2),(1,2,3,4,5,6,7,8)]) sage: one = P.one() sage: perm = libgap.eval('[]') sage: %timeit one._generate_new_GAP(perm) The slowest run took 138.45 times longer than the fastest. This could mean that an intermediate result is being cached. 1000000 loops, best of 3: 174 ns per loop sage: %timeit P.one()._generate_new_GAP(perm) The slowest run took 77.00 times longer than the fastest. This could mean that an intermediate result is being cached. 1000000 loops, best of 3: 220 ns per loop
comment:109 Changed 9 months ago by
 Dependencies set to #25608
comment:110 Changed 9 months ago by
 Commit changed from 1be187efe05a7ee899d3a715380cb636aa29c1c0 to 82244f3b70201460fd979e8537b20007d5e99829
Branch pushed to git repo; I updated commit sha1. New commits:
82244f3  Merge branch 'develop' into t/25477/enumerate_PermutationGroup

comment:111 Changed 9 months ago by
 Commit changed from 82244f3b70201460fd979e8537b20007d5e99829 to 1d1e70cf8fb96c7381f655c534078be65766cfd9
Branch pushed to git repo; I updated commit sha1. New commits:
1d1e70c  updated and extended doctests

comment:112 in reply to: ↑ 106 Changed 9 months ago by
 Status changed from needs_work to needs_review
Again ready for review!
 This is dangerous:
<GapElement_List> lst_in
since you don't know thatlst_in
is aGapElement_List
. Either do an explicitisinstance()
check or use<GapElement_List?>lst_in
.I would like to do
cpdef _generate_new_GAP(self, GapElement_List lst_in)
but do not know how
this is still open.
comment:113 followup: ↓ 163 Changed 9 months ago by
 Branch changed from u/stumpc5/enumerate_PermutationGroup to u/tscrim/iteration_permutation_groups25477
 Commit changed from 1d1e70cf8fb96c7381f655c534078be65766cfd9 to 83d485a9e424a35566190d548aee64f7c89fe088
 Reviewers changed from Christian Stump, Dima Pasechnik to Christian Stump, Dima Pasechnik, Travis Scrimshaw
So I don't understand the comment about iterations. So I removed it. However, if SGS is not consistent across different computers, we have a problem with doctests. The RES is guaranteed to have a fixed iteration order, so I can only assume the SGS does not have such a guarantee. I changed the doctests to what I needed for them to pass, but I am guessing they will fail for you. If they pass for you and SGS is consistent, then the comment should have been removed anyways.
I made a few other tweaks.
New commits:
83d485a  Reviewer changes.

comment:114 Changed 9 months ago by
 Keywords days94 added
comment:115 followup: ↓ 116 Changed 9 months ago by
Thanks Travis!
 G = libgap.Group(self.gens()) + G = libgap(self) #libgap.Group(self.gens())
I chose the first because it was slightly faster. Also I wanted to keep
 # the following also works but is much slower:  #gap2sage = lambda elt: one._generate_new(libgap.ListPerm(elt).sage())  #gap2sage = lambda elt: libgap.ListPerm(elt)._generate_perm(one)
to see the other but slower ways to do this.
 in the two algorithms, and is not even guaranteed to always  be the same for one of the two.
This now depends on gap behaviour, also I prefer not to guarantee that I will not change the output when changing the implementation. Anyways, if you prefer to remove it, that's fine too.
comment:116 in reply to: ↑ 115 Changed 9 months ago by
Replying to stumpc5:
Thanks Travis!
 G = libgap.Group(self.gens()) + G = libgap(self) #libgap.Group(self.gens())I chose the first because it was slightly faster.
I get the latter is faster:
sage: A = PermutationGroup([(1,2),(1,2,3,4,5,6,7,8,9)]) sage: %timeit libgap.Group(A.gens()) The slowest run took 13.32 times longer than the fastest. This could mean that an intermediate result is being cached. 10000 loops, best of 3: 53.5 µs per loop sage: %timeit libgap(A) The slowest run took 4.21 times longer than the fastest. This could mean that an intermediate result is being cached. 10000 loops, best of 3: 35.6 µs per loop
Also I wanted to keep
 # the following also works but is much slower:  #gap2sage = lambda elt: one._generate_new(libgap.ListPerm(elt).sage())  #gap2sage = lambda elt: libgap.ListPerm(elt)._generate_perm(one)to see the other but slower ways to do this.
Commented out code gets removed quite quickly by other people and looks bad to put slower code. The data is in the history if someone wants to look it up.
 in the two algorithms, and is not even guaranteed to always  be the same for one of the two.This now depends on gap behaviour, also I prefer not to guarantee that I will not change the output when changing the implementation. Anyways, if you prefer to remove it, that's fine too.
If a particular version of GAP is consistent, than no comment is necessary (a number of doctests typically change when GAP upgrades). We have never guaranteed an output order for group iteration, so I don't see any point in mentioning it.
comment:117 Changed 9 months ago by
Okay, let's see which doctests have to be undated (given the new ordering of the permgroup iteration).
comment:118 Changed 9 months ago by
 Branch changed from u/tscrim/iteration_permutation_groups25477 to u/stumpc5/iteration_permutation_groups25477
comment:119 Changed 9 months ago by
 Cc rbeezer added
 Commit changed from 83d485a9e424a35566190d548aee64f7c89fe088 to 63d057d7e21b3f0f52ac990486ebd4efd07755de
I updated the permutation group iteration order in judsonabstractalgebra
and cc'ed Rob Beezer her as requested there.
New commits:
63d057d  fixed doctests in judsonabstractalgebra

comment:120 followup: ↓ 134 Changed 9 months ago by
Currently, the slow iteration using RecursivelyEnumeratedSet
uses depth first search with generators being the group generators. Which of the following would you prefer:
 Depth or breadth first search ?
 Generators or generators plus their inverses?
I would think that bfs would be a more natural ordering, especially for small groups that you actually look at and see how the Cayley graph is propagated. Using also inverses is another question and I don't actually have a preference. Sometimes generating sets for Cayley graphs are expected to also contain inverses, sometimes not.
comment:121 followup: ↓ 140 Changed 9 months ago by
while you are at it, could you fix the doc for PermutationGroupElement?
It appears that what you get from sage: PermutationGroupElement?
has not made it into the corresponding rst file, e.g. it's not possible to see an example with an explicit parent in the reference manual (in section http://doc.sagemath.org/html/en/reference/groups/sage/groups/perm_gps/permgroup_element.html)
Also, an example with an explicit parent out to be given in Examples, not in Tests only.
comment:122 Changed 9 months ago by
 Commit changed from 63d057d7e21b3f0f52ac990486ebd4efd07755de to 596dc649a793f90cc072185d0fb2caa7d18eb3a5
comment:123 followup: ↓ 133 Changed 9 months ago by
I fixed a few more doctests, not done yet. Let me mention that I find it questionable (and risky) that so many doctests fail due to this change of iteration...
comment:124 Changed 9 months ago by
to me, this rather shows that make doctests depend upon an order which need to be preserved is not a good idea in the first place...
comment:125 Changed 9 months ago by
yes, and even more is true: some doctest pick out some unspecified element
sage: SGA.group() Symmetric group of order 4! as a permutation group sage: SGA.an_element()  () + 2*(1,2) + 4*(1,2,3,4) + () + (1,2,3,4) + 2*(1,3)(2,4) + 3*(1,4)(2,3)
do stuff with it
sage: G = SymmetricGroup(4).algebra(QQ) sage: G.retract_plain(G.an_element(), 3)  () + 2*(1,2) + ()
which might be boring for other elements (such as here), or even pick special elements with intended properties from it
sage: D = DihedralGroup(5) sage: elements = D.list(); elements  [(), (1,5)(2,4), (1,2,3,4,5), (1,4)(2,3), (1,3,5,2,4), (2,5)(3,4),  (1,3)(4,5), (1,5,4,3,2), (1,4,2,5,3), (1,2)(3,5)]  ~~~~~~~~~~~~~~~~~~~~~~ ::   sage: rotate = elements[2]  sage: flip = elements[3]
comment:126 followup: ↓ 132 Changed 9 months ago by
I would have rewritten the test
sage: SGA.an_element() ...
as
sage: SGA.an_element() in SGA True
etc...
comment:127 Changed 9 months ago by
 Commit changed from 596dc649a793f90cc072185d0fb2caa7d18eb3a5 to a9fb42bf2d314a6bde076d3d4ca0d2c1801c4a80
Branch pushed to git repo; I updated commit sha1. New commits:
a9fb42b  fixed some more doctests

comment:128 Changed 9 months ago by
 Commit changed from a9fb42bf2d314a6bde076d3d4ca0d2c1801c4a80 to a6d7793fd090de56b0609d5ba6c6f22ab287b660
comment:129 Changed 9 months ago by
 Commit changed from a6d7793fd090de56b0609d5ba6c6f22ab287b660 to 55d5c64a0e0e7d28ae5b78120f70d069f8cd028c
Branch pushed to git repo; I updated commit sha1. New commits:
55d5c64  implemented breadth and depth first search iteration

comment:130 Changed 9 months ago by
 Commit changed from 55d5c64a0e0e7d28ae5b78120f70d069f8cd028c to 9504bc275b11c5f3deb57c7aab937f01858aa903
Branch pushed to git repo; I updated commit sha1. New commits:
9504bc2  fixed more doctests

comment:131 Changed 9 months ago by
 Commit changed from 9504bc275b11c5f3deb57c7aab937f01858aa903 to 97ce6291fbc34d4d760b6433d32f9196b347a34d
Branch pushed to git repo; I updated commit sha1. New commits:
97ce629  more doctests

comment:132 in reply to: ↑ 126 Changed 9 months ago by
Replying to dimpase:
I would have rewritten the test
sage: SGA.an_element() ...as
sage: SGA.an_element() in SGA Trueetc...
Well, the generic element is usually generic enough to be useful. This test only works when testing _an_element_
. It is used elsewhere to show how the element changes.
comment:133 in reply to: ↑ 123 Changed 9 months ago by
Replying to stumpc5:
I fixed a few more doctests, not done yet. Let me mention that I find it questionable (and risky) that so many doctests fail due to this change of iteration...
I agree there is some risk, but a good review should be checking that it is just an order difference. So generically, I would say your concern is misplaced. However, I am very worried there is an order dependency on the machine, which means we have write more annoying doctests (i.e., calling sorted
a lot).
comment:134 in reply to: ↑ 120 ; followup: ↓ 136 Changed 9 months ago by
Replying to stumpc5:
Currently, the slow iteration using
RecursivelyEnumeratedSet
uses depth first search with generators being the group generators. Which of the following would you prefer:
 Depth or breadth first search ?
 Generators or generators plus their inverses?
I would think that bfs would be a more natural ordering
I would just let it run its default, but if I had to choose, I would say BFS as well.
comment:135 Changed 9 months ago by
Also one little thing, but could you break the long output line in sage/categories/finite_dimensional_lie_algebras_with_basis.py
(like how it was before).
comment:136 in reply to: ↑ 134 ; followup: ↓ 137 Changed 9 months ago by
Replying to tscrim:
I would just let it run its default, but if I had to choose, I would say BFS as well.
Well, we now have the three options SGS, BFS, DFS. I think that should be okay now...
comment:137 in reply to: ↑ 136 Changed 9 months ago by
comment:138 Changed 9 months ago by
Dear Christian,
Thanks very much for the cc on the changes to Judson's AATA. I'll be able to do a diff and even more quickly discern what has changed. I'm waiting on 8.3 to do a new update for the book, so this may miss that cutoff, but that should not be a crisis by any means. Thanks everyone for your work keeping this code working well.
Rob
comment:139 Changed 9 months ago by
 Commit changed from 97ce6291fbc34d4d760b6433d32f9196b347a34d to b586d0c3ab19a30a6004d04fb373286cb9d35a86
Branch pushed to git repo; I updated commit sha1. New commits:
b586d0c  added examples of perm gp elts into documentation

comment:140 in reply to: ↑ 121 Changed 9 months ago by
comment:141 Changed 7 months ago by
I know, I need to finish a review of this (including doing a rebase). This might also conflict with #26045. This is now been able to become high on my todo list.
comment:142 Changed 7 months ago by
 Branch changed from u/stumpc5/iteration_permutation_groups25477 to public/group_theory/improve_iterator_perm_gps25477
 Commit changed from b586d0c3ab19a30a6004d04fb373286cb9d35a86 to ca2d1b3bdecc3544afd400f21151fe81d096a794
 Dependencies changed from #25608 to #25608 #26045
 Milestone changed from sage8.3 to sage8.4
I have rebased it to 8.4.beta1 and over #26045. However, let's let this run on some patchbots to see if there is any machine dependency (in addition, if some of the other people here can do so). If there are no doctest failures, then we are safe to assume the SGS iterator is not machine dependent. With that, I would be okay setting a positive review.
New commits:
19f82d1  various fixes for py3 in combinat and root_systems

7456780  pyflakes cleanup in one file

3c25ec3  fix sorting key for affine root systems

4a2c244  Merge branch 'u/chapoton/26045' in 8.4.b1

79c25c9  Merge branch 'u/stumpc5/iteration_permutation_groups25477' of git://trac.sagemath.org/sage into public/group_theory/improve_iterator_perm_gps25477

ca2d1b3  Fixing doctests due to bad rebase and some doc tweaks.

comment:143 Changed 6 months ago by
 Commit changed from ca2d1b3bdecc3544afd400f21151fe81d096a794 to 1b00bf24882d4a3cf2e38380501c4d76a926fc93
Branch pushed to git repo; I updated commit sha1. New commits:
1b00bf2  merged

comment:144 Changed 6 months ago by
@tscrim: what to do with these doctest failures?
comment:145 Changed 6 months ago by
 Commit changed from 1b00bf24882d4a3cf2e38380501c4d76a926fc93 to f226bc3953195da299e35f8b2b2bbb34264cb097
Branch pushed to git repo; I updated commit sha1. Last 10 new commits:
5af3439  Fix the erroneous fix of some corner cases

138f85b  Turn some functions of polynomial.hilbert to methods of ETuple

e900222  Hilbert series: Remove unnecessary bound checks, simplify code branches

f0e5c85  Add documentation to new ETuple methods

2d29b9b  Using slices, custom median, and formatting/P#P8 tweaks to Hilbert code.

07ff2e1  Reverting use of get_exp for __getitem__.

7b2ed50  Merge branch 'u/tscrim/hilbert_functions26243' of git://trac.sagemath.org/sage into u/tscrim/hilbert_functions26243

5637e07  Fixing INPUT:: to INPUT: in hilbert.pyx.

10f3921  Merge branch 'public/group_theory/improve_iterator_perm_gps25477' of git://trac.sagemath.org/sage into public/group_theory/improve_iterator_perm_gps25477

f226bc3  Fixing trivial doctest failures.

comment:146 Changed 6 months ago by
 Commit changed from f226bc3953195da299e35f8b2b2bbb34264cb097 to dddbcf33c4e8113862e127b26ca5a9e6e6d62267
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
dddbcf3  Fixing trivial doctest failures.

comment:147 Changed 6 months ago by
Since #26225 is now in Sage, those doctest should essentially be sorted (or given by a fixed ordering). So this should fix those. Also you were missing a blank line in one of the book tests.
(Sorry about the noise, I was not based on develop. Fixed in the last forced push.)
comment:148 followup: ↓ 150 Changed 6 months ago by
Only
File "src/sage/tests/books/judsonabstractalgebra/permutesage.py", line 268, in sage.tests.books.judsonabstractalgebra.permutesage Failed example: H.list() Expected: [(), (1,3), (4,5), (1,3)(4,5)] Got: [(), (4,5), (1,3), (1,3)(4,5)]
seems to be left. What kind of sorting do you want there?
comment:149 Changed 6 months ago by
 Commit changed from dddbcf33c4e8113862e127b26ca5a9e6e6d62267 to 1a3a69aab4d4f681c9e6237dc8bdfaa17fc93def
Branch pushed to git repo; I updated commit sha1. New commits:
1a3a69a  Fix the ordering of one more test.

comment:150 in reply to: ↑ 148 Changed 6 months ago by
Replying to stumpc5:
What kind of sorting do you want there?
I suspect that is just a leftover from the test not being run. I doubt it is machinedependent, so the fix I just pushed should take care of it.
comment:151 Changed 6 months ago by
okay, this seems to be ready to go!
comment:152 Changed 6 months ago by
 Status changed from needs_review to positive_review
comment:153 followup: ↓ 154 Changed 6 months ago by
 Status changed from positive_review to needs_work
Can you have a look at the patchbot output: Python3 incompatible code inserted on 1 nonempty lines. Also, tests fail
sage t long src/sage/geometry/polyhedron/ppl_lattice_polytope.py # 1 doctest failed
comment:154 in reply to: ↑ 153 Changed 6 months ago by
Replying to vbraun:
Can you have a look at the patchbot output: Python3 incompatible code inserted on 1 nonempty lines.
That is libGAP code on that line (comes from the libgap.function_factory("""
), so it is not Python3 incompatible.
Also, tests fail
sage t long src/sage/geometry/polyhedron/ppl_lattice_polytope.py # 1 doctest failed
I think I forgot to run the long
when I checked this locally (and so I concluded that it was a spurious patchbot fault). However, I did confirm this locally. It seems like the group is too large to pass to libgap:
sage: libgap(aut) # the group from the test in question python2: libgap.c:184: libgap_get_input: Assertion `strlen(libGAP_stdin_buffer) < length' failed.
It has 1152 generators! However gap
handles this fine.
So I just reverted the first change on comment:115, and that seems to fix the problem. I can see how that is more safe as I am surprised libgap
is passing things by strings. Which might account for the fact that @stumpc5 and me got different timing results.
comment:155 Changed 6 months ago by
 Commit changed from 1a3a69aab4d4f681c9e6237dc8bdfaa17fc93def to 1a85742fa2577f9612fe1df3ac7faad52e2ee050
Branch pushed to git repo; I updated commit sha1. New commits:
1a85742  Using libgap.Group(self.gens()) to avoid input string limits via libgap(self).

comment:156 Changed 6 months ago by
 Status changed from needs_work to needs_review
comment:157 followup: ↓ 159 Changed 6 months ago by
Its the Weyl group of F4...
libgap is passing by strings but there is an assumption that it fits into a certain buffer. This could be fixed...
comment:158 Changed 6 months ago by
Why on Earth one generates all the 1152 elements of W(F_4)? This looks like something really weird in the implementation...
comment:159 in reply to: ↑ 157 Changed 6 months ago by
Replying to vbraun:
Its the Weyl group of F4...
Right, but the computation uses all of the elements as generators, which is what makes it blowout the buffer.
libgap is passing by strings but there is an assumption that it fits into a certain buffer. This could be fixed...
I agree, but this is the less invasive (and easier) change. Ideally a PermutationGroup
and its elements would directly construct the object in libgap using the C data structures.
comment:160 Changed 6 months ago by
That change annoyingly causes the output order to change... So, should we fix the output order (again) or revert 1a85742 and do a more proper fix of the libgap interface?
comment:161 Changed 6 months ago by
What exactly is happening in the latest commit? Do you mean to say that before it
libgap(bla)
, for bla
a permutation group, caused all the elements of bla
to be listed?! If so, this was certainly a bug.
comment:162 Changed 6 months ago by
No, I am saying that libgap(bla)
and libgap.Group(bla.gens())
results in a different iteration order (at least in Sage) of the group elements.
comment:163 in reply to: ↑ 113 Changed 6 months ago by
Replying to tscrim:
So I don't understand the comment about iterations. So I removed it. However, if SGS is not consistent across different computers, we have a problem with doctests. The RES is guaranteed to have a fixed iteration order, so I can only assume the SGS does not have such a guarantee. I changed the doctests to what I needed for them to pass, but I am guessing they will fail for you. If they pass for you and SGS is consistent, then the comment should have been removed anyways.
SGS is often computed with a randomisation involved, and so one cannot guarantee the same chain of subgroups across different runs on the same machine. If you fix the base to be used, you'd have less variance, but still there could be randomisation involved in choosing the ordering of the base elements.
We should not tweak algorithms in order to make testing easier, we should tweak tests, anyway.
What is RES?
comment:164 Changed 6 months ago by
RES = RecursivelyEnumeratedSet
.
comment:165 Changed 6 months ago by
 Commit changed from 1a85742fa2577f9612fe1df3ac7faad52e2ee050 to 916cea6571eb56c3c88d54cd3373476030ce501c
comment:166 Changed 6 months ago by
I've just updated the doctests to reflect the change in ordering (or remove the dependence on the ordering). So if the patchbots come back green, I think we can set this back to a positive review (that should be reasonable enough confirmation that the doctest outputs are not machinedependent).
comment:167 Changed 6 months ago by
One green patchbot and one almost green. I don't see how the error in computing the volume of a polytope could be caused by this ticket, so I suspect it is an unrelated failure.
comment:168 Changed 6 months ago by
 Status changed from needs_review to positive_review
Let us get this in. The polyhedral computation stuff done, as in the doctest in question, over RDF, is dodgy anyway (more so as it is done on PPC64, of all platforms), and I don't see how it can have anything to do with this ticket.
comment:169 Changed 6 months ago by
 Status changed from positive_review to needs_work
Merge conflict
comment:170 Changed 6 months ago by
 Commit changed from 916cea6571eb56c3c88d54cd3373476030ce501c to ca255bbfb94ace207a6b87a4d364310786315dd1
Branch pushed to git repo; I updated commit sha1. New commits:
ca255bb  Merge branch 'develop' into public/group_theory/improve_iterator_perm_gps25477

comment:171 Changed 6 months ago by
 Status changed from needs_work to positive_review
Trivial merge conflict.
comment:172 Changed 6 months ago by
 Status changed from positive_review to needs_work
File "src/sage/rings/number_field/galois_group.py", line 137, in sage.rings.number_field.galois_group.GaloisGroup_v1.group Failed example: list(P) # optional  database_gap Expected: [(), (1,2), (1,2,3), (2,3), (1,3,2), (1,3)] Got: [(), (1,2,3), (1,3,2), (2,3), (1,2), (1,3)] ********************************************************************** 1 item had failures: 1 of 5 in sage.rings.number_field.galois_group.GaloisGroup_v1.group [142 tests, 1 failure, 3.05 s]  sage t long src/sage/rings/number_field/galois_group.py # 1 doctest failed
comment:173 Changed 6 months ago by
Just sort these doctest results with something stable and platformindependent...
comment:174 Changed 6 months ago by
 Commit changed from ca255bbfb94ace207a6b87a4d364310786315dd1 to 648e61cfc2a3e207d254631a055f006c8a847b8e
Branch pushed to git repo; I updated commit sha1. New commits:
648e61c  Fixing database_gap doctest.

comment:175 Changed 6 months ago by
 Status changed from needs_work to needs_review
It actually is not machinedependent, it was just not tested by the patchbots because it is marked with an optional gap package to make sure there were no others (well, there was one also marked with magma, but I cannot test that one).
comment:176 Changed 6 months ago by
I don't think this is a right fix. Any new version of GAP might mess this up... How about
sage: set(list(P)) {(), (2,3), (1,2), (1,2,3), (1,3,2), (1,3)}
or
sage: sorted(list(P)) [(), (2,3), (1,2), (1,2,3), (1,3,2), (1,3)]
comment:177 Changed 6 months ago by
 Commit changed from 648e61cfc2a3e207d254631a055f006c8a847b8e to 6c634093d2d26be5837470c8325ff92cbfa3d9ca
Branch pushed to git repo; I updated commit sha1. New commits:
6c63409  Using sorted on doctest.

comment:178 Changed 6 months ago by
I'm not a fan of decorating doctests that don't really need it, but I've added it.
comment:179 Changed 6 months ago by
 Status changed from needs_review to positive_review
comment:180 Changed 6 months ago by
 Status changed from positive_review to needs_work
On 32bit:
********************************************************************** File "src/sage/geometry/polyhedron/library.py", line 360, in sage.geometry.polyhedron.library.Polytopes.icosahedron Failed example: ico.volume() Expected: 2.1816949907715726 Got: 2.181694990771572 ********************************************************************** 1 item had failures: 1 of 11 in sage.geometry.polyhedron.library.Polytopes.icosahedron [211 tests, 1 failure, 118.70 s]  sage t long src/sage/geometry/polyhedron/library.py # 1 doctest failed
comment:181 Changed 6 months ago by
oh, and that's why: the icosahedron generator contains
verts = [p(v) for p in AlternatingGroup(3) for v in pts] return Polyhedron(vertices=verts, base_ring=base_ring, backend=backend)
how about we just add ...
to that doctest, like 2.18169499...
?
comment:182 Changed 6 months ago by
 Commit changed from 6c634093d2d26be5837470c8325ff92cbfa3d9ca to 693ada71485226cf82fa700c9a1c3d4201d3b404
Branch pushed to git repo; I updated commit sha1. New commits:
693ada7  Adding rel tol to polyhedron/library.py test.

comment:183 followup: ↓ 184 Changed 6 months ago by
 Status changed from needs_work to positive_review
I added a rel tol
in case there ends up being other slight numerical differences in the future.
comment:184 in reply to: ↑ 183 Changed 6 months ago by
Replying to tscrim:
I added a
rel tol
in case there ends up being other slight numerical differences in the future.
The digits after 2.18169499
are not right, for the exact evaluation gives
2.18169499062...
.
sage: (5/12*sqrt(5) + 5/4).n() 2.18169499062491
That's why I'd prefer truncation as I suggested.
comment:185 Changed 6 months ago by
 Status changed from positive_review to needs_review
I think that is part of the point of the doctest, that it is different. If you insist, I will change it to truncation, but I also believe that suggests a much larger numerical instability than is actually present.
comment:186 Changed 6 months ago by
IMHO it is not an instability, it is an artefact of naive computing with finite precision, i.e. accumulation of a rounding error.
comment:187 Changed 6 months ago by
 Commit changed from 693ada71485226cf82fa700c9a1c3d4201d3b404 to 3ec5057ee13ac5450b3b7a2ddba09c2c4aa772c7
Branch pushed to git repo; I updated commit sha1. New commits:
3ec5057  Changing to truncated version.

comment:188 followup: ↓ 189 Changed 6 months ago by
 Status changed from needs_review to positive_review
Okay, that is not quite the right terminology. It still suggests that there is significantly more variation in the doctest than what it really has. However, I changed it because I want this to get in and don't want it cut from the next stable release.
comment:189 in reply to: ↑ 188 Changed 6 months ago by
Replying to tscrim:
Okay, that is not quite the right terminology. It still suggests that there is significantly more variation in the doctest than what it really has. However, I changed it because I want this to get in and don't want it cut from the next stable release.
It rather illustrates that RDF is not a field, and that it isn't even commutative... There could be more variation coming from a yet another CPU used. E.g. if you have a better FPU then you might get closer to the correct value, which would again break the doctest if it had too much numerical noise left.
comment:190 Changed 6 months ago by
 Branch changed from public/group_theory/improve_iterator_perm_gps25477 to 3ec5057ee13ac5450b3b7a2ddba09c2c4aa772c7
 Resolution set to fixed
 Status changed from positive_review to closed
I added an alternative suggestion
__iter_alt__
in the patch. However, sometimes calculation the strong_generating_system takes much longer than actually iterating with the standard iterator above. Here are some timing experiments:Any suggestions? What are good other groups to do benchmarking?
New commits:
a suggestion for an alternative iterator