Re: [sage-support] Re: Strange results in DiGraph.girth()

2012-10-29 Thread Georgi Guninski
On Sun, Oct 28, 2012 at 07:17:59AM -0700, Nathann Cohen wrote: Well, the documentation says Computes the girth of the graph. For directed graphs, computes the girth of the undirected graph. So, that's what you are getting. :) By the way, perhaps it is a bad idea to have this

Re: [sage-support] Re: Strange results in DiGraph.girth()

2012-10-29 Thread P Purkayastha
On Monday, October 29, 2012 2:59:43 PM UTC+8, Georgi Guninski wrote: On Sun, Oct 28, 2012 at 07:17:59AM -0700, Nathann Cohen wrote: Well, the documentation says Computes the girth of the graph. For directed graphs, computes the girth of the undirected graph. So,

Re: [sage-support] Re: Strange results in DiGraph.girth()

2012-10-29 Thread Georgi Guninski
On Mon, Oct 29, 2012 at 02:35:47AM -0700, P Purkayastha wrote: I wonder if it is less computationally demanding to walk around the graph than take powers of M, especially for large, but sparsely connected graphs. May be you are right. Powers of the matrix appear easier to implement IMHO.

Re: [sage-support] Re: Strange results in DiGraph.girth()

2012-10-29 Thread Nathann Cohen
May be you are right. Powers of the matrix appear easier to implement IMHO. After some reading I don't think you can do better than O(n^(3-epsilon)) because of odd cycles. Ahahaahah. Well, implement the Matrix version and I will implement the graph thing. We could be checking the results

Re: [sage-support] Re: Strange results in DiGraph.girth()

2012-10-29 Thread Georgi Guninski
On Mon, Oct 29, 2012 at 01:29:43PM +0100, Nathann Cohen wrote: May be you are right. Powers of the matrix appear easier to implement IMHO. After some reading I don't think you can do better than O(n^(3-epsilon)) because of odd cycles. Ahahaahah. Well, implement the Matrix version and I

[sage-support] Cholesky for sparse matrix

2012-10-29 Thread Raniere Gaia Silva
Hi, I need to performe a (numerical) cholesky factorization of a sparse matrix (20x20) but I'm getting a error. I look at this thread https://groups.google.com/forum/?fromgroups=#!searchin/sage-devel/cholesky/sage-devel/AW4pmKx49H4/7iuet3rWYQgJ but it didn't help very much (and is a little old).

[sage-support] What's wrong with sagenb ?

2012-10-29 Thread Christophe BAL
Hello, the following code takes more than one minute to acheive its job. Is there some technical problem with the server ? Christophe Simple code = def pgcdBoucle(a, b): n = 0 if b a: a, b = b, a while(b != 0): a, b = b, a%b n += 1 return

Re: [sage-support] What's wrong with sagenb ?

2012-10-29 Thread William Stein
On Mon, Oct 29, 2012 at 12:26 PM, Christophe BAL projet...@gmail.com wrote: Hello, the following code takes more than one minute to acheive its job. Is there some technical problem with the server ? Yes, it doesn't know French. Get rid of the e with the accent over it in : print

[sage-support] Re: What's wrong with sagenb ?

2012-10-29 Thread Jason Grout
On 10/29/12 2:41 PM, William Stein wrote: On Mon, Oct 29, 2012 at 12:26 PM, Christophe BAL projet...@gmail.com wrote: Hello, the following code takes more than one minute to acheive its job. Is there some technical problem with the server ? Yes, it doesn't know French. Get rid of the e

Re: [sage-support] Re: What's wrong with sagenb ?

2012-10-29 Thread Christophe BAL
Happy to find one bug. [?] Christophe 2012/10/29 Jason Grout jason-s...@creativetrax.com On 10/29/12 2:41 PM, William Stein wrote: On Mon, Oct 29, 2012 at 12:26 PM, Christophe BAL projet...@gmail.com wrote: Hello, the following code takes more than one minute to acheive its job. Is