getting a grip on memory usage

[Jeffrey Palmer]

On Wednesday 22 May 2002 12:48 pm, Hal Daume III wrote:
> so i have a function that is eating *tons* of memory.  my application
> is clustering and i put everything in UArrays or Arrays.  for
> clustering 5 data points with 4 features (a tiny tiny set) the
> program gobbles 350mbs!  most of the usage is coming from this
> distance function:
>

Ahh, a fellow memory abuser.  ;)

I recently ran into very similar behavior while implementing a Haskell=20
rendering engine.  I was using a lookup table deep within a loop, and=20
references to the lookup table seemed to be allocated as each=20
computation was deferred.  I immediately allocated over 150MB for a=20
very simple render.

Try turning on heap profiling, and see if you get anything interesting. =20
There is an option to display "named" references (or something like=20
that) that might provide insight into what's responsible.

In my case, I rewrote my monad to be stricter (and used case), and=20
forced a result data structure to be strict in its components.  This=20
forced complete evaluation of all of the elements prior to returning=20
the result.  I don't know if you have a nice place to put something=20
like that, but it's worth a look.

When all was said and done, my application memory usage never went above=20
4MB, which is exactly where I expected it to be.

Check out this link:

http://users.aber.ac.uk/ajc99/stricthaskell.html

It has some interesting ways of forcing evaluation at various times,=20
etc., although I prefer other ways of obtaining these results. =20
However, it is a good list of candidate changes for debugging.

Enjoy!

=09- j


--=20
The river is moving.
The blackbird must be flying.