On Wed, Nov 11, 2009 at 9:51 AM, Bryan O'Sullivan <b...@serpentine.com>wrote:
> On Wed, Nov 11, 2009 at 7:43 AM, David Leimbach <leim...@gmail.com> wrote: > >> >> I recently ran into some serious space leak difficulties that would >> ultimately cause this program to crash some time after startup (my simulator >> is also written in Haskell, and runs a LOT faster than the real application >> ever could, this has enabled me to fast forward a bit the data growth issues >> and crash in minutes instead of days!) >> > > It sounds to me like you were storing a Map in a StateT. Since the usual > State and StateT monads don't force the evaluation of their payload, I'm not > terribly surprised that such a leak should arise. > That's exactly what was happening. The system was being far too lazy (by choices I made but didn't fully understand). By pulling the Map out of the state, and pushing it back into the state, as the definition of my looping, things got a lot better. I didn't see another *easy* way to force the state to be evaluated, except by doing IO on intermediate values. seq will only evaluate strictly if it's just underneath something else that's already been evaluated :-). The runtime doesn't look for "seq"s to force evaluation on. I figured I was better off just creating a dependency in the evaluation, near the outermost portion of the program (the loop) that would cause a strict evaluation, and so far I was right :-) Program behaves very well now, and responds much better too. Dave
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