Hi, As some of you may know¹, I've been playing around with associative data structures, and in particular Judy arrays, using the "judy" package by Don S. Now, I find these to be fast and (more importantly) frugal concerning memory - but now I see what I can only interpret as memory corruption - a bit depending on the ordering of the code and/or insertion of print statements, output is truncated or contaminated. The strange thing is that this only occurs when I also use Data.Vector or Data.HashTable.IO in the same program - if it's all Judy, then things work as expected - as far as I have seen, anyway. First I thought it was my dubious "insertWith" function, but when I reverted to separate "insert" and "lookup", I can still provoke the behavior. Has anybody else seen anything similar? Any idea how to debug something like this? Then I thought I'd look at hash tables, using the 'hashtables' package. I haven't tested it much yet, but it appears to be a lot slower than Judy (maybe as much as 10x), and uses a lot more memory (also perhaps a factor of 10). I guess I might be able to improve things a bit by judiciously applying strictness, but it seems to be storing both keys and values unboxed, so I don't expect to come close to Judy - I guess there isn't any unboxed hash table implementations around? Anyway - I seem to have programmed myself into a corner here, so suggestions welcome! -k ¹ http://blog.malde.org/posts/frequency-counting.html and http://blog.malde.org/posts/k-mer-counting.html -- If I haven't seen further, it is by standing in the footprints of giants