Zappa Mexico II Release Notes 1/25/2008

1. Changelist:

added futility/extended futility pruning a lot of speed optimizations that were mostly eliminated by calling eval() at every node singular extensions are now automatically disabled for >8 cores max hash table size increased to 1TB ! some very small extra eval terms.

Overall not a lot; this is strictly a maintenance upgrade. Should be similar to the original Zappa Mexico in most positions except for (hopefully) getting a bigger depth due to extra pruning. Perhaps +20 elo can be expected. 2. Instant Move

I have gotten some questions about this. Zappa will move instantly whenever a move is singular, i.e. much better than the others. It's a feature, not a bug :) These are not always immediately obvious recaptures, but if you analyze in multipv mode the alternatives to the singular move should always be considerably lower in score (> 0.5 pawns).

3. Strelka

Since this release comes immediately after the release of the Strelka source code, I assume that there will be a hue and cry from the unwashed masses about how I am pirating the intellectual property of Vasik Rajlich. Let me just immediately say that there are simply no new ideas in Strelka anyway; my shock at reading the Strelka source code was not generated by the brilliancies contained therein but by the lack thereof. Looking at Strelka finally convinced me to do some things that everyone else has done for a long time (like futility pruning), and to clean up my code a bit since I had always been developing in "crunch" mode. I did not add any eval terms from Strelka (my view being that Zappa's eval is way better than Strelka's anyway) and I also did not do the crazy futility pruning where it drops into the qsearch at depth 3. In summary, Strelka was more a source of motivation than chess ideas. Of course, you will just have to take my word for it until some enterprising Russian hacker disassembles Zappa :)

4. Opening Book

I have also gotten some questions about an opening book for Zappa. My current recommendation is Sedat Canbaz's confidently named Perfect.ctg for Chessbase GUIs, free from SedatChess.com.

enjoy,

anthony