Re: Array.ST is not being nice to me

Chris Kuklewicz wrote:

...

So my theory now is: I do a large number of lookups.

Try using Data.Array.Base.unsafeRead (and maybe ata.Array.Base.unsafeWrite). These avoid the bounds checking on the index each time you lookup something in the array.

Right. Also keep an eye on the GC time (+RTS -sstderr) if you're using boxed mutable arrays - we don't do card-marking, so GC is pretty sub-optimal when it comes to large mutable boxed arrays. Decreasing the number of GCs with +RTS -A<big> can help if you're suffereing from this - but always try with and without, sometimes it makes things worse by making less effective use of the L2 cache. Cheers, Simon