Hi Lemmih,
Have you tried profiling the code? You can find a guide to profiling with GHC here: http://www.haskell.org/ghc/docs/latest/html/users_guide/profiling.html
I did that ... it shows that updateState is retaining most data (-hr switch), as well as updateMap, which is increasing it's retained set towrd the end, whereas the updateState simply rocks off to high levels and then gradually descends. I'm not sure how to fix that. Obviously, the methodStack will grow and shrink up to the depth of the execution stack of my application, but that should be about it. the System stack is also quite big as far as retained data goes, declining quite slowly up to the end of the execution. My gut feeling tells me that I should make sure the update of the state is actually evaluated and not simply kept around. But I've no idea how to get that to happen. -- Andy