Ketil Malde writes:

Is it an idea to go back a few steps to more idiomatic code?

I had a whirl at the 'reverse complement' benchmark, where we're in the Java ballpark for performance and memory, but at twice the code size. My simple implmentation is down from seventy to about forty lines, perhaps thirty-five if I remove comments etc. The bad news is that it's about twice as slow, my benchmark takes about 0.45s vs 0.25 for the shootout entry. One interesting observation is that 'map' from Data.ByteString working directly on Word8 is actually *slower* than 'map' from Data.ByteString.Char8. Anyway - it occurs to me that this can fairly simply be sped up by parallelizing: chunk the input, complement chunks in parallel, and reverse. Any takers? -k -- If I haven't seen further, it is by standing in the footprints of giants

Felipe Lessa writes:

On Thu, Apr 29, 2010 at 10:54:09AM +0200, Ketil Malde wrote:

...

Anyway - it occurs to me that this can fairly simply be sped up by parallelizing: chunk the input, complement chunks in parallel, and reverse. Any takers?

Do you mean, something like this?

Yes, that's exactly what I mean (you also need to reverse each chunk for this particular problem). Of course, it remains to see how well it performs in practice - it's not something I would expect to get right at the first attempt (I haven't used parallelism much so far). Several of the shootout benchmarks suffer from using only one CPU, so given Haskell/GHCs claim for easy concurrency, there should be some relatively low-hanging fruit there. -k -- If I haven't seen further, it is by standing in the footprints of giants

ketil:

Don Stewart writes:

...

http://shootout.alioth.debian.org/u64q/haskell.php

Observations:

Although we're mostly beaten on speed, and about the same on code size, we're using a lot less memory than Java.

Prior to the upgrade we weren't mostly beaten on speed, so I think a bit of tuning (ghc -server :) should help.

jason.dusek:

2010/04/30 Don Stewart :

...

Prior to the upgrade we weren't mostly beaten on speed, so I think a bit of tuning (ghc -server :) should help.

What do you mean by that? I tried searching the flags page:

http://www.haskell.org/ghc/docs/6.12.2/html/users_guide/flag-reference.html

I couldn't find a server flag.

Java has a server flag, sort of like defaulting to -H1G -N4 etc. -- Don