As of late I've been fiddling with a rather simple AI chatterbot. Nothing remarkably clever, learns from input, generates sentences from keywords, so on, so forth. This particular bot has been around for a couple of months now and has managed to learn a great many things.
Recently I queried why it was taking up so much memory. Now I have a better understanding, and as its grown, I realise that I most certainly do need to attempt to use something different for storing the data in memory.

The data consists of two large hash of hashes, linking a keyword to potential following symbols and a weighting count. On disk, uncompressed, this takes up some 6.5M for some 120,000 possible word combinations. In memory this takes up 70M. Thats a big difference.
My understand is that perl, in its infinite and speedy wisdom, preallocates memory when it generates the hash, so when you add elements, you aren't constantly reallocating memory. As the word base has grown, it's become apparent that learning slows as he sees fewer and fewer things that he doesn't already know. Logical. This means he infrequently is adding new things to his data set. More importantly, of the 120,000 hashes, some 90% of them have less than 4 entries... Thats a lot of wasted preallocated memory.
So what I'm wondering is, is there an existing hash structure (That I can use, ala tie()) that doesn't preallocate? This way I'm only allocating memory that I actually need? I can stand the tradeoff in speed, right about now.

If this doesn't already exist, what suggestions do you have for building my own? (I'd figure I'd rip-off the existing built-in perl code for doing hashes and just have it not preallocate)...

My thanks
JP Hindin
-- Alexander Widdlemouse undid his bellybutton and his bum dropped off --