I wrote:
Dear Hets- and GHC-Developers,
we have a problem using ghc-6.6.1. The created hets binary runs a couple of times slower than the one created using ghc-6.6.
This problem is gone when I install and use fgl-5.3 (where "hiding (indices)" needs to be deleted in Data.Graph.Inductive.Monad.IOArray). I strongly suspect the new functions context1l' and context4l' in Data.Graph.Inductive.Graph (fgl-5.4.1) to be the reason for our drastic slow down. In fgl-5.3 the functions fst4 and fth4 have been used instead. A cyclic edge (an edge from and to the very same node) was only returned as ingoing edge and not as outgoing one. (a design decision documented elsewhere). I think, the change in fgl-5.4.1 now returns a cyclic edge also as outgoing edge (and possibly twice as ingoing one). Our application heavily uses in- and outgoing edges that may be cyclic. Christian P.S. ghc-6.6.1/libraries/fgl/Setup.hs does not compile with ghc-6.6.1