[Haskell-cafe] mtlx has a nice design but is slow

[Don Stewart]

Typically you'll want to inline any definitions of >>= and return in
your classes and instances. Also, any non-recursive top level wrapper
functions.

On Wed, Apr 6, 2011 at 3:00 PM, Mark Snyder <muddsnyder at yahoo.com> wrote:
> I'm the author for mtlx, and admittedly I didn't do anything about
> efficiency when I implemented it.  Is there any initial place I ought to
> look for tips on inlining? I'll start with the pragmas page
> (http://www.haskell.org/ghc/docs/7.0.3/html/users_guide/pragmas.html) I
> suppose.  I'm happy for any suggestions--optimizing hasn't been one of my
> focuses, so it's time for me to learn I suppose!
> I did switch to newtype definitions in the most recent version (0.1.5),
> which probably helped a lot compared to data definitions, but there are no
> inline pragmas in use, so perhaps there are some good opportunities for
> optimization.
> ~Mark Snyder
>>
>>Is the package missing some obvious inlining in the instances?
>>
>>> I just refactored my type and transform system prototype (introduced in
>>> [1]
>>> but changed since then) from using mtlx [2] (type-indexed monad
>>> transformers
>>> described in [3]) to mtl using RWST. mtlx allowed me to cleanly separate
>>> the
>>> various monadic components in a convenient way. Unfortunately, I found it
>>> to
>>> be too slow. The refactoring was an experiment to see how slow. I was
>>> rather
>>> surprised:
>>>
>>> Running time of a compiled main with a list of tests:
>>> ? mtlx (7 transformers): 2 min 52 sec
>>> ? mtl (RWST): 0 min 13 sec
>>>
>>> It's frustrating to see such a huge performance gap for a better design.
>>>
>>> Regards,
>>> Sean
>>>
>
>
>
>
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