Poker Stats: Auto-detecting Full Tilt Poker Hand History

Here's a gory report of some technical internals of my app. If Java or concurrent programming bores you, avert your eyes.

Yesterday I completed the mechanism to detect the user's Full Tilt Poker hand history. I'm pleased with the result. It gave me a chance to give the java.util.concurrency API a good work out. I have the interesting challenge of keeping the GUI responsive while performing some processor intensive parsing. I got to write a simple implementation of Google's MapReduce algorithm too.

Here's what happens: my Poker stats app scans for hand history files in the ~/Documents/HandHistory folder, which is where Full Tilt Poker writes its hand history, unless instructed otherwise. This folder can be changed in the preferences.

A background thread is launched to monitor this folder. Any file that has either not been parsed yet, or has changed in file size since last parsed is added to a list of files to be parsed. This process is repeated every 10 seconds. To be precise, it is repeated 10 seconds after the end of the previous scan. Through careful monitoring I've proven that this regular scanning causes no discernible ongoing load on the system.

The list of files needing scanning is then sent to the parser. I've used every trick I know to make the parser fast. On my dual core 2.4 Ghz Mac Book Pro, it currently rips through the hand history files at the rate of about 2500 hands per second, although it sometimes peaks at 4000 hands per second. On a multi-CPU or multi-core processor, my MapReduce implementation creates multiple parsing threads, so this rate could feasibly be much higher. I'll have to find a way to test this on a machine with more than 2 cores.

As soon as all the hands in a file are parsed, the GUI is notified to update, via the Observer pattern. Newest files are parsed first, so that upon start-up the most recent statistics appear immediately, whereas the older stats may take a few seconds to appear.