I just released chess4j 3.2. This release is purely about optimizing for speed. That is, there are no changes to the search or evaluation terms.
chess4j is now a bitboard engine, and uses magic bitboards for move generation. Simply by replacing some loops over all squares with loops over (possibly sparsely populated) bitboards, and probably most importantly getting rid of some managed collections stuff, chess4j 3.2 is 4-5x faster than 3.1. In a head to head match of almost 700 games with 3.1, 3.2 scored 79% which translates into a 200-250 elo gain.
One other important difference is that the opening book is now off by default. If you want to use the opening book included with the release, you must add “-book=book.db” to the command line. (This is done in the included chess4j.bat.)
I think I can still get some more ELO just off speed optimizations and efficiency improvements (such as splitting up capture and noncapture move generation), so there will probably be one more release in the 3.x line before moving onto 4.0. The 4.x line will be focused on parallel search.
As usual you can grab the latest and greatest from the project website. Enjoy!