Dima's profile - activity

I guess plot tries to smoothen the graph, doing an interpolation, or a spline, something that needs a numerical derivati

I posted a branch which apparently fixes the problem, but I don't really know why.

That's a bug, indeed. I opened https://trac.sagemath.org/ticket/34597 for matrices over cyclotomics a multi-modal algor

That's a bug, indeed. I opened https://trac.sagemath.org/ticket/34597

nothing to do with sagecell, it can be reproduced in Sage: gap.eval('LoadPackage("qpa");Q:=Quiver(3,[[1,2,"a"],[2,3,"b

Does this work in terminal? (i.e. at sage: prompt)

this is an oldish bug, same happens with almost 3 years old https://github.com/pynac/pynac/releas...

I've opened https://trac.sagemath.org/ticket/29832

with the notation of the answer by @rburing, you probably need

sage: IA._naive_ideal(IA.ring()).groebner_basis()
[z0*z1*z6 - z5, z1*z3 - 1, z3^2 - z0*z5, z0*z4 - z3, z3*z4 - z5, z4^2 - z1*z6, z1*z5 - z4, z3*z5 - z0*z6, z4*z5 - z6, z5^2 - z3*z6, z2 - 1]

the difference with the Macaulay2 answer is probably due to a different monomial order used. (In Sage computation it's the default order used).

Unfortunately our Macaulay2 insterface is brokek atm: https://doc.sagemath.org/html/en/refe...

That 'neglex' order (a local order, not a proper Groebner basis order) looks out of place there. Without it, the saturations of the naive ideal with x_i are already done, so the answer shoud be the same as the naive ideal.

I've edited the answer to indicate this.

In a way, everything which is possible in GAP is also possible in Sage, as Sage starts up a GAP subprocess and communicates with it. So you need not have Sage bindings for every GAP function. E.g. you can do

sage: g=SymmetricGroup(7)  
sage: gap("Orbits("+str(g._gap_())+","+str(tuples([1..7],2))+",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 ] ] ]

Nowadays (Sage version 8.6 or newer) one can do

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 ] ] ]

Reported on https://github.com/fredrik-johansson/...

indeed it seems to be a Python3 issue.

To use system's readline on on Ubuntu 16.04, one needs to install libncurses5-dev and libreadline-dev (16.04 has a bug: the former is not a dependency of the latter, even though by right it should be)

As far as building Sage's readline goes, unfortunately we have not figured out yet what exactly goes wrong with building Sage's readline on 16.04. As a workaround, in the file build/pkgs/readline/patches/0002-ltinfo.patch replace the line

+       SHLIB_LIBS='$(TERMCAP_LIB)'

with

+   SHLIB_LIBS='-ltinfo -lncurses'

This shoud give a working readline built by Sage (hopefully)

this is a symptome of underlinking in readline. In its infinite wisdom readline's devs refuse to fix this old bug; it needs to be linked with libtinfo or other suchlike library, and it keeps resufacings in various forms...

OVA is more awkward than the Cygwin build, so that's why it stopped. You might want to try Sage 8.8 http://www.mirrorservice.org/sites/ww...

Or if you comfortable with VirtualBox (or other VM) on Windows, you may just build Sage there from source.

Yes, semidefinite optimisation is available in Sage, check out

http://doc.sagemath.org/html/en/refer...

put that one like into a file, and source it every time you want to start anaconda. (Better, make a script that sources this line and starts Anaconda for you).

In ipython there are special tools for this (I guess they are used in e.g. Jupyter notebook environment to save the state), see e.g. https://stackoverflow.com/questions/2...

Thanks. This is the fix (the whole id_label business was a leftover from an old buggy implementation of the modular decomposition, now replaced with this one. Will be fixed in the upcoming release.

diff --git a/src/sage/graphs/graph.py b/src/sage/graphs/graph.py index 617881e4a7..57504aaecd 100644
--- a/src/sage/graphs/graph.py
+++ b/src/sage/graphs/graph.py
@@ -7180,9 +7180,7 @@ class Graph(GenericGraph):

         D = modular_decomposition(self)

-        id_label = dict(enumerate(self.vertices()))
-
-        relabel = lambda x : (x.node_type, [relabel(_) for _ in x.children]) if x.node_type !=NodeType.NORMAL else id_label[x.children[0]]
+        relabel = lambda x : (x.node_type, [relabel(_) for _ in x.children]) if x.node_type != NodeType.NORMAL else x.children[0]

          return relabel(D)

thanks, see https://github.com/sagemath/sagenb/is... for this problem.

Well, but this is a straightforward Python loop to write. In the loop, create two lists, say, ro, co, using range(), remove i-th (resp. j-th) elements from it, call A[ro,co].det()/A[ro,ro].det() to compute the corr. determinant ratio, store it in B.

I imagine that scipy does not convert the pseudo-inverse exactly. Anyhow, please specify the example of a graph on which you see the problem.

there is a little 'V' field under the answer score counter on the right, which one ticks to accept the answer. I just did it here.

You can create lists of rows and columns and use them to cut out a submatrix. E.g.

 sage: M=matrix([[1,2,3,4],[3,4,5,6],[6,7,8,9]])
 sage: M[[0,2],[0,2]]
 [1 3]
 [6 8]

no, not really. See https://arxiv.org/pdf/math/9909177.pdf for bounds and examples. E.g. in dimension 13 you might have more than 17000000 facets.

this depends on the input quite a bit. Namely, the following factors play a big role:

• how many facets your polytope $P$ has
• how big in abs. value the coordinates of your points are (assuming they are all integers)
• how degenerate $P$ is; i.e. the maximal number of neighbours of a vertex of $P$ --- the more degenerate it is, the slower the facet enumeration)

Why would you think this is Singular problem? Univariate polynomials are not handled by Singular in Sage, they are handled by either Flint, or NTL, or Givaro (the latter for finite fields only). We need more info to track your issue down. E.g. could you at least tell us the output of type(f) for your polynomial f?

I presume the question is about how to build a quadratic extension of GF(8) explicitly.

Here is an example of how to get a list of coset representatives:

sage: g=libgap.AlternatingGroup(5)
sage: h=g.Stabilizer(1)
sage: [x.Representative() for x in g.RightCosets(h)]
[(), (1,5,4), (1,4,5), (1,2,5), (1,3,5)]

Please feel free to ask for more details.

I am not 100% sure that you want to start with the permutation group - it might be a proper quotient of the "real" group, and then you need to do something else.

 sage: g=libgap.Group(map(lambda s: libgap.PermList(s.get_perm()), Gautgens))

will give you the underlying permutation group. It has 1 orbit in its natural action (on 8 points):

 sage: g.Orbits()
 [ [ 1, 2, 5, 3, 6, 4, 7, 8 ] ]

You can convert it into a matrix group acting on GF(4)^8.

 sage: mg=libgap.Group(map(lambda s: libgap.PermutationMat(s,8,libgap.GF(4)), g.GeneratorsOfGroup()))

Now you can compute orbits on vectors (see e.g. code in graphs/generators/classical_geometries.py for details); however, you might want to make sure that GAP's GF(4) is created in a compatible way.

sounds like you've changed the default OS configuration, as on OSX the system python is still python2, and this means that you won't see any missing brackets in print, normally speaking. What is that extra hack that you have on? Homebrew? Anaconda? Something else?

I take this as you have an upgraded Mac, right? And which version of OSX? (IMHO it's a non-standard config anyway, and you'd be best off building from source.)

please see https://github.com/sagemath/sagenb/is...

numpy in Sage uses Atlas for matrix operations; if you use a binary Sage installation then Atlas might be not optimised for your hardware. To get good Atlas performance, the best is to build Sage from source.

I very much doubt that there are closed form solutions for such a system. It looks like this would imply that univariate polynomial equations of arbitrary degrees have a closed form solution, which is well-known not to be the case.

as a last resort, open the terminal, run latex or pdflatex there...