[Haskell-cafe] "Out of memory" if compiled with -O2, why?

[Jason Dagit]

On Wed, Dec 1, 2010 at 6:23 AM, Dmitry Kulagin <dmitry.kulagin at gmail.com>wrote:

> Hi,
>
> I have problems with memory leaks and can't find out how to avoid them.
> I tried to reduce sample to demonstrate the following problems:
> 1) when compiled without -O2 option, it iconsumes 1582MB (!) total memory
> 2) when compiled with -O2 option it terminates with "out of memory"
>
> Actually I don't understand the reasons, particulary why  GC can't
> collect already processed objects g,...,n (see code below)?
>
> I would appreciate very much any help with this situation.
> Thanks!
>
>
> module Main where
>
> import qualified Data.Map as M
>
> len = 15*1024*1024
> lst from = take len $ zip [from..] [0..]
>
> g = M.size $ M.fromList $ lst 0
> h = M.size $ M.fromList $ lst 0
> i = M.size $ M.fromList $ lst 0
> j = M.size $ M.fromList $ lst 0
> k = M.size $ M.fromList $ lst 0
> l = M.size $ M.fromList $ lst 0
> m = M.size $ M.fromList $ lst 0
> n = M.size $ M.fromList $ lst 0
>
> main = do
>    mapM_ print [g,h,i,j,k,l,m,n]
>

I'm using ghc7 here.  If I run your program with -O2, it takes 1943 MB of
memory max.

If I comment out everything except g and h then with -O2 it takes 1521 MB.

If I comment out everything except g then with -O2 it takes 1521 MB.

I'm not sure where the extra 400 MB of memory are going.

When I compile with: -fno-cse -fno-full-laziness and -O2, the memory usage
(with g though n) is 1585 MB.

Jason
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