Array.ST is not being nice to me

[Simon Marlow]

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