[Haskell-cafe] Re: Breaking cycles in a directed graph.

[C Rodrigues]

I ran across this problem a while ago, working on identifying edges in 
dependence cycles for software pipelining.  The problem you want to solve is 
known as the "minimum feedback arc set" problem and is NP-hard.  In my case, 
I could use other knowledge about the problem domain to find a good 
approximate solution.

I'll refer you to the Wikipedia article: 
http://en.wikipedia.org/wiki/Feedback_arc_set

I hope that helps.