Well, I'm sorry to say it like that, but as David mentionned this
document is really outdated now, which mean I have been thinking about
rewriting all of it. Actually, I already wrote an introduction to
graphs and LP using Sage, which should soon be available as a part of
the (french) Sagebook, but I intended o translate it next week.
I am really sorry I was not able to review patches or answer messages
these last days as efficiently as usual : I have been backpacking for
2 weeks, which is extremely nice for the mind but does not get coding
done. I will be unavailable for something like a week and a half
again, which I will spend unable to reach internet. I hope to be able
to post patches for a real graph tutorial, along with a real LP
tutorial (and not these "constructions" things -- they were moved to
the "construction" document because they relied on an (formerly)
optional package -> GLPK), up to date and (I hope) interesting.
> 1. The maximal matching example code does not like my fix.
> I probably just messed up the objective function. Anyone see the fix?
Your objective function is fine. The problem is the unsatisfiable
constraint that for any edge b[u][v] + b[v][u] == 1. It means that
exactly one of these two edges has to be "taken". As the Petersen
graph is 3-regular, it means that the sum of the weights of the edges
adjacent to each vertex is at least 1.5, which is not a matching. It
should be nicer if you remove the min = 1 in this constraint.
Of course, if this mistake was mine, please receive my humblest
(Oh, and you probably want the variables to be binary)
> 2. I tried to install GLPK on one machine following the instructions
> in this same document, but it failed.
GLPK is now installed by default, and its behaviour has been changed
recently. Would I be right in guessing you are using an old version of
> I followed the same process on another machine and it worked fine.
> How do I debug this?
Same running version of Sage ? Anyway, GLPK is now installed by