[Haskell-cafe] sha1 implementation thats "only" 12 times slower then C

[Donald Bruce Stewart]

aeyakovenko:
> So I tried implementing a more efficient sha1 in haskell, and i got to
> about 12 times slower as C.  The darcs implementation is also around
> 10 to 12 times slower, and the crypto one is about 450 times slower.
> I haven't yet unrolled the loop like the darcs implementation does, so
> I can still get some improvement from that, but I want that to be the
> last thing i do.
> 
> I think I've been getting speed improvements when minimizing
> unnecessary allocations.  I went from 40 times slower to 12 times
> slower by converting a foldM to a mapM that modifies a mutable array.
> 
> Anyone have any pointers on how to get hashElem and updateElem to run
> faster, or any insight on what exactly they are allocating.  To me it
> seems that those functions should be able to do everything they need
> to without a malloc.

Try inlining key small functions, and check the core.

    -O2 -ddump-simpl | less

-- Don