On Thursday, March 24, 2016 at 2:20:56 PM UTC, Jernej wrote: > > Thanks. I wasn't aware that passing the group to libgap will actually try > to pass all of its elements to gap! > It does not pass all of its elements, certainly. It passes the generators, as a string, and this string is too long in your example. The workaround I suggested passes each generator separately. So this would also break on groups with about 10 higher degree...
> Continuing on the topic though I have two new questions about this libgap > magic. > > When doing g.Orbits(tuples([1..7],2),libgap.OnTuples) are the tuples > actually computed in Sage and passed to gap? The reason I am trying to call > directly is to make sure this is computed in gap, where I am (blindly) > assuming it's faster. > here, naturally, tuples() is a Python function. > > Finally, if I want to repeat the example using combinations it seems that > the obvious conversion fails > > g.Orbits(combinations([1..7],2),libgap.OnSets) > > gives the (expected) NameError: name 'combinations' is not defined, > > capitalizing combinations gives > > ValueError: libGAP: Syntax error: ; expected > Combinations of [1, 2, 3, 4, 5, 6, 7] of length 2; > GAP functions need a prefix sage: g.Orbits(libgap.Combinations([1..7],2),libgap.OnTuples) [ [ [ 1, 2 ], [ 2, 3 ], [ 2, 1 ], [ 3, 4 ], [ 1, 3 ], [ 3, 2 ], [ 4, 5 ], [ 2, 4 ], [ 4, 3 ], [ 3, 1 ], [ 5, 6 ], [ 3, 5 ], [ 1, 4 ], [ 5, 4 ], [ 4, 2 ], [ 6, 7 ], [ 4, 6 ], [ 2, 5 ], [ 6, 5 ], [ 5, 3 ], [ 4, 1 ], [ 7, 1 ], [ 5, 7 ], [ 3, 6 ], [ 1, 5 ], [ 7, 6 ], [ 6, 4 ], [ 5, 2 ], [ 7, 2 ], [ 6, 1 ], [ 4, 7 ], [ 2, 6 ], [ 1, 7 ], [ 7, 5 ], [ 6, 3 ], [ 5, 1 ], [ 6, 2 ], [ 3, 7 ], [ 1, 6 ], [ 2, 7 ], [ 7, 4 ], [ 7, 3 ] ] ] alternatively, you could do (almost) the same as follows: sage: g.Orbits(libgap([1..7]).Combinations(2),libgap.OnTuples) By the way, we have a recent trac ticket allowing to get rid of libgap. prefix, but it's not merged (yet). > > > Best, > > Jernej > > > > On Thursday, 24 March 2016 07:36:55 UTC+1, Dima Pasechnik wrote: >> >> >> >> On Wednesday, March 23, 2016 at 11:10:42 PM UTC, Jernej wrote: >>> >>> Hello! >>> >>> Thanks! I wasn't aware of libgap! One more followup question. Say I want >>> to compute the orbits of the CubeGraph of order 10. The description of >>> respective automorphism group seems to be to heave for libgap >>> >>> ==== >>> sage: G = graphs.CubeGraph(10) >>> sage: G.relabel() >>> sage: A = G.automorphism_group() >>> sage: libgap(A) >>> python: libgap.c:186: libgap_get_input: Assertion >>> `strlen(libGAP_stdin_buffer) < length' failed. >>> === >>> >>> Is there a way to overcome this limitation? >>> >> >> sage: G = graphs.CubeGraph(10) >> sage: A = G.automorphism_group() >> sage: T=libgap.Group(map(libgap,A.gens())) >> sage: T.Order() >> 3715891200 >> >> works. >> There is probably a fixed side buffer somewhere that is not big enough >> for passing the whole of A >> directly. >> >> >>> Best, >>> >>> Jernej >>> >>> On Tuesday, 22 March 2016 14:18:56 UTC+1, Dima Pasechnik wrote: >>>> >>>> >>>> >>>> On Tuesday, March 22, 2016 at 1:09:07 PM UTC, Dima Pasechnik wrote: >>>>> >>>>> use libgap: >>>>> >>>>> sage: g=libgap.SymmetricGroup(7) >>>>> sage: g.Orbits(tuples([1..7],2),libgap.OnTuples) >>>>> [ [ [ 1, 1 ], [ 2, 2 ], [ 3, 3 ], [ 4, 4 ], [ 5, 5 ], [ 6, 6 ], [ 7, 7 >>>>> ] ], [ [ 1, 2 ], [ 2, 3 ], [ 2, 1 ], [ 3, 4 ], [ 1, 3 ], [ 3, 2 ], [ 4, 5 >>>>> ], [ 2, 4 ], [ 4, 3 ], [ 3, 1 ], [ 5, 6 ], [ 3, 5 ], [ 1, 4 ], [ 5, 4 ], >>>>> [ >>>>> 4, 2 ], [ 6, 7 ], [ 4, 6 ], [ 2, 5 ], [ 6, 5 ], [ 5, 3 ], [ 4, 1 ], [ 7, >>>>> 1 >>>>> ], [ 5, 7 ], [ 3, 6 ], [ 1, 5 ], [ 7, 6 ], [ 6, 4 ], [ 5, 2 ], [ 7, 2 ], >>>>> [ >>>>> 6, 1 ], [ 4, 7 ], [ 2, 6 ], [ 1, 7 ], [ 7, 5 ], [ 6, 3 ], [ 5, 1 ], [ 6, >>>>> 2 >>>>> ], [ 3, 7 ], [ 1, 6 ], [ 2, 7 ], [ 7, 4 ], [ 7, 3 ] ] ] >>>>> >>>>> if you only need representatives, you can just use map: >>>> >>>> map(lambda x: x[0], g.OrbitsDomain(tuples([1..7],2),libgap.OnTuples)) >>>> >>>> (Here I used OrbitsDomain, which you should use for efficiency if you >>>> know that your set is invariant under your >>>> group) >>>> >>>> >>>>> On Tuesday, March 22, 2016 at 9:19:18 AM UTC, Jernej wrote: >>>>>> >>>>>> Hello! >>>>>> >>>>>> I have a few questions concerning GAP interface in Sage 7.x. >>>>>> >>>>>> I have a permutation group G acting on a set S and I would like to >>>>>> compute the representatives of the orbits of G acting on k-sets of S. >>>>>> >>>>>> I recall that a while ago I could do the following (as seen on this >>>>>> example >>>>>> http://ask.sagemath.org/question/9652/orbits-on-group-actions-acting-on-sets/?answer=14470#post-id-14470 >>>>>> ) >>>>>> >>>>>> ==== >>>>>> sage: g=SymmetricGroup(7) >>>>>> sage: >>>>>> gap("Orbits("+str(g._gap_())+","+str(tuples([1..7],2))+",OnTuples)") >>>>>> ==== >>>>>> >>>>>> and yes, it works in Sage 6.x. However, in Sage 7.x one gets the >>>>>> following error >>>>>> >>>>>> ==== >>>>>> TypeError: Gap terminated unexpectedly while reading in a large line: >>>>>> Gap produced error output >>>>>> Error, Permutation: cycles must be disjoint and duplicate-free >>>>>> ==== >>>>>> >>>>>> Given this, I have the following questions >>>>>> >>>>>> - What is the proper way to call gap in Sage 7x t obtain the orbits >>>>>> of a group G acting on k-sets of a set S? >>>>>> - (GAP question) I recall there is a way to return only the >>>>>> representatives of the orbits? Anyone happens to recall the right GAP >>>>>> command for that? >>>>>> - Does it make sense to add an option for various group actions to >>>>>> Sage directly (as is already done for specific orbits ) ? >>>>>> >>>>>> Best, >>>>>> >>>>>> Jernej >>>>>> >>>>> -- You received this message because you are subscribed to the Google Groups "sage-support" group. 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