Dear Simon and Dima,
I moved this to https://trac.sagemath.org/ticket/24924 for better
traceability and to show you some code snippets...
Cheers, Christian
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Dear Simon,
Anyway, looking at sage/graphs/bliss.pyx, it seems easy to modify your
> code to directly create a bliss graph.
>
Help there is highly appreciated :-), I don't know how to do that
appropriately...
Christian
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Dear Dima,
Ultimately, the classical canonical form/isomorphism implementations run on
> (di)graphs represented by 0-1 matrices, often
> with bit entries. So that's how bliss_digraph is represented too.
>
Thanks for this info clarifying that it seems impossible to feed the
algorithm any other
Hi Simon,
Thanks for trying! I was actually hoping for a way to completely avoid
creating this sage DiGraph. But either to get the matrix directly into the
algorithm (which currently seems impossible), or at least to directly
construct some internal graph data structure.
Looking at the code
Dear Johan,
> The most inefficient part of _matrix_to_digraph seems to be the
> following line:
>
> > x = edge_labels.index((a,b))
>
you are totally right, thanks for this suggestion! (Unfortunately, this
will not change anything in practice, because the list
Let me add that the situations I care about are n,m <= 20, the entries are
<=5 and the matrices are sparsely filled. An random and typical example is
sage: M = matrix([(0, -1, 0, 0, 0, 0, 0, 1),
: (1, 0, 1, 0, 0, 0, 0, 0),
: (0, -1, 0, 0, 1, 0, 0, 0),
: (0, 0, 0, 0, 0, 1, 0, 0),
(This question is about speed improvements of an existing approach, not
about finding a first toy solution.)
Let A, B be two ( (n+m) x n ) integer matrices. Say that these are
isomorphic if they coincide up to *simultaneous* row and column
permutations of the indices 0,...,n-1.
Example:
> There is a code for generating posets, see attachment at
> https://trac.sagemath.org/ticket/14110 , but unfortunately it has not
> been
> integrated to Sage. I just tested and it takes about 2,2 seconds to
> generate 11-element posets (there are 46749427 of those) and 38 seconds
> for
> How big is your n?
>
not very big, I aim for the biggest n for which I can loop through all
permutations of n and compute some numbers. I expect this to be between 10
and 14.
> "Almost all" finite posets are connected, so uniform distribution of all
> posets would work too for bigger
>
> 0) take a connected random graph (call graphs.RandomGNP in a loop, until
> you get something connected)
> 1) take a random ordering of vertices, say v1,v2,...,vn.
>
2) orient each edge (vi,vj) in the direction j>i.
>
This last step is actually a good idea, I didn't think of this way of
Is there a way to obtain a random connected poset on n unlabelled elements
in sage?
Random preferably means uniformly at random, but other randomness might be
okay if it is not too far away from uniform. Generating all posets,
checking for connectedness and picking is way too slow.
Hi,
how can I generate, in a fast enough way, connected graphs for which the
clique complex is pure, ie, for which all containmentwise maximal cliques
are of the same size ?
Fast enough here means that I can produce examples of such graphs with 20
vertices, edge degrees between 10 and 14 (an
> I spent most of the last week at a Macaulay2 workshop, and actually
playing with M2<->Sage interface :-)
> here you are:
Awesome, thanks!
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> YES.
thanks, that's the first step -- I did actually mean so that I get the
output as Sage objects. Sorry for not saying that explicitly...
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The method "word_problem" for a permutation group element can be found at
http://doc.sagemath.org/html/en/reference/groups/sage/groups/perm_gps/permgroup_element.html#sage.groups.perm_gps.permgroup_element.PermutationGroupElement.word_problem
But if the permutation group G is finite, I
>
> In short, the Gröbner fan knows the correct ordering (in terms of a weight
> vector) but Sage's output presents the basis with a different ordering.
> This caused me no small amount of confusion. Is this a feature, or a bug?
>
I ran into this very same issue today -- to get a functionality
Many thanks, works well and fast enough!
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Hi there,
is the functionality to get *ALL* hamiltonian cycles in a graph somehow
already available in Sage? (Mathematica provides that,
http://reference.wolfram.com/language/Combinatorica/ref/HamiltonianCycle.html,
but I would prefer not to pay for each hamiltonian cycle I am offered by my
Hi there,
I wonder how to parallelize the following scenario.
I have a method that initiates a (not very simple) data strucure and then
runs a for-loop (of, say, length 1,000-20,000) to populate that data
structure with data. The computations in each loop is not trivial, but
fairly optimized
Thanks, William!
It absolutely will use two additional *processes*, as you might see by
watching with htop, top, or using ps.
Is it right that the master process is creating all the subprocesses?
I'd suspect I don't quite see the other processes in action simply
because they are there only for
I encourage you to read the source code of this @parallel stuff --
it's only about 2 pages of actual code,
which I wrote at some Sage days as my project back in maybe 2008.
Will do, thanks again!
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Hello,
can anyone tell me how I can use sage to check that the following two
(fairly simple) expressions coincide. Some unneeded background: both come
from identities in character theory for complex reflection groups, Sage was
able to solve similar expressions, see below, and this is the
Okay, I got the simplification by doing
sage: f.expand().simplify()
while
sage: f.simplify()
or
sage: f.simplify_full()
did actually not work...
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Hello --
I want to do some computations with multivariate polynomials in the group W
of type H4 (14400 elements). I have a summand for every element w \in W,
and a product of 4 polynomials in each summand:
gens = []
for obj in gens_objects:
p = 0
for w in W:
mon_w =
Hello,
we constructed some modules over the path algebra, and then the hom
space using Hom.
- How can we actually see that we computed the hom space over the
algebra rather than as vector spaces over the base field? We tried
getting out the dimension as a test, but there seems to be no way to
do
of this quotient having again finite
vector space dimension.
In the example, the subring is generated by x1, x2, x3,
x1*y1+x2*y2+x3*y3, x1^2*y1+x2^2*y2+x3^2*y3, x1^3*y1+x2^3*y2+x3^3*y3.
Is there any construction solving this kind of problem?
Thanks for your help, Christian Stump
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m=[0.6158, 0.5893, 0.5682, 0.51510, 0.4980, 0.4750, 0.5791,
0.5570,0.5461, 0.4970, 0.4920, 0.4358, 0.422, 0.420]
m.count
len(m) does the job, you should probably look into the tutorial at
http://www.sagemath.org/doc/tutorial/ for this kind of questions...
m.count is a function returning the
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