[Haskell-beginners] Understanding program stack usage

[Rafael Gustavo da Cunha Pereira Pinto]

GHC profiling is not that hard. There are a few tutorials on the Internet
that can help you (try Real World Haskell, ch
25<http://book.realworldhaskell.org/read/profiling-and-optimization.html>)

Running your code with "+RTS -pa -sstderr" can give you some hints on where
it is hogging memory.

Regards.

Rafael

On Wed, Apr 27, 2011 at 15:25, Patrick LeBoutillier <
patrick.leboutillier at gmail.com> wrote:

> Felipe,
>
> I tried the $! bit, but I get the same result. I guess there's another
> leak somewhere...
>
> Patrick
>
> On Wed, Apr 27, 2011 at 11:20 AM, Felipe Almeida Lessa
> <felipe.lessa at gmail.com> wrote:
> > On Wed, Apr 27, 2011 at 11:52 AM, Patrick LeBoutillier
> > <patrick.leboutillier at gmail.com> wrote:
> >> How do I figure out why the program needs a lot of stack?
> >
> > Usually it is because you are building a large thunk.
> >
> >> Also, is there an easy way to increace performance?
> >
> > Getting rid of the thunks should increase performance as well.
> >
> > I've had just a quick look on your code, but here are some suggestions:
> >
> >> record :: (Ord n) => n -> Distrib n -> Distrib n
> >> record n (Distrib m rs) = Distrib (M.alter f slot m) rs
> >>  where f (Just n) = Just $ n + 1
> >>        f Nothing = Just 1
> >>        slot = findSlot n rs
> >>        findSlot x (r@(Range a b):rs)
> >>          | x >= a && x < b = r
> >>          | otherwise       = findSlot x rs
> >>        findSlot x []       = OutOfBounds
> >
> > Try changing "Just $ n + 1" to "Just $! n + 1".  It is possible that
> > this change alone removes the leak (it is the only obvious leak I'm
> > seeing right now).
> >
> > Also, for findSlot you may want to do a binary search, but that isn't
> > related to the leak at all.
> >
> > Cheers,
> >
> > --
> > Felipe.
> >
>
>
>
> --
> =====================
> Patrick LeBoutillier
> Rosemère, Québec, Canada
>
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-- 
Rafael Gustavo da Cunha Pereira Pinto
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