now i see what you mean. no, i mean trivial transformation. #650 says about slow GC. why it's slow? because once you made any update to the array, the entire array is marked as updated and scanned on next minor GC (which occurs after every 512 kbytes allocated, afaik). let's replace big array (say, of 10,000 elements) with array of 100 arrays of 100 elements each. now, between minor GCs only some of arrays will be changed and entire amount of memory to be scanned will become less Data.IntMap? I want to implement a more-or-less traditional, mutable, imperative hash table in the ST monad. Hence, I'm not considering Data.IntMap and other persistent tree structures for its implementation, although I have thought about it. The bug described in Ticket #650, AFAICS, prevents implementation of a reasonable, generic hash table in Haskell. :-(
Data.IntMap is just a limit of what Bulat suggested. So what was you thoughts about Data.IntMap in mutable hashmap?