A new site claims to have all flavors of Rybka 4.0 engine available for download (Including SSE4 and Chess960 versions), much before the official release date (May 28th?)
Note: I have neither tested these nor endorse you download these. Download/Use these at your own risk. Remember that Rybka is relatively cheap, compared to CB engines, so I seriously suggest buying the full Rybka (CB GUI) version. Having said that, pick up what you can while that site lasts
Rybka4 download site: http://avenger999.blogspot.com/
Now, regarding what is new in Rybka4: Here’s the Rybka4 release notes (draft) posted in rybkaforum.net today by Vasik Rajlich:
May 26, 2010
Rybka 4 is the latest UCI Rybka chess engine. The changes since Rybka 3 are extensive.
– The evaluation is more accurate and better aware of king safety and other dynamic factors.
– The search is more efficient in every major category of position.
– Some new endgame heuristics have been added.
– The overall engine behavior has been cleaned up and made less quirky.
– New parameters controlling engine output, engine priorities, and engine time management during game play.
– Ability to take advantage of large memory pages (_link_) and SSE4.2 and SSE4a instruction sets.
– New logging capability, which documents in .html the evolution of the main line for all analyzed positions.
– Asymmetrical piece scoring (see below).
Asymmetrical piece scoring
It is now possible to adjust all piece values for both colors in Rybka 4. This functionality has three uses:
1) Rybka can be informed that some pieces in some specific position should or should not be traded.
2) Setting higher overall piece values for one color implements contempt. Rybka will attempt to not trade the more valuable pieces, keeping more tension in the position, and she will give higher evaluation scores to the side with the more valuable pieces and therefore avoid draws by repetition.
3) Piece values which are more consistent with top GM practice can be used. For still-unknown reasons, rooks and queens tend to be more valuable in computer play than what top human players believe to be correct. The default values are optimized for computer play. GM Larry Kaufman recommends the following adjustments as more human-like: pawns=0, knights=24, bishops=24, rooks=12, queens=0. (_link_)
Please note that contempt is now off by default and should be set manually when appropriate.
Please see the Rybka 4 user area (_link_) or visit our forum (_link_) for more information.
A huge thanks to everyone on the Rybka team, as well as to everyone else who has contributed in any way.
– Lukas Cimiotti, for systematically pushing our clustering project through all sorts of ups and downs to being the weapon and asset which it is today, and for the comically shocking effect produced by his mountain of hardware.
– Jiri Dufek, for an awesome Rybka 4 book, for his pragmatic and highly successful tournament preparation, and also for some useful networking skills.
– Jeroen Noomen, for the groundbreaking Rybka 3 books, for several years of superb tournament preparation, and for making sure that Hans stays out of trouble.
– Nick Carlin, for his unique scientific brand of book preparation, for delivering several tournament victories in a short but productive period of time, and for returning to make sure that Rybka 4 was done right.
– Felix Kling and Christoph Kling for our excellent web site, for interesting reports, and for keeping the forum free from marauding bandits.
– Larry Kaufman, for his innovative man vs machine matches, for countless suggestions about quantitative aspects of Rybka‘s evaluation, and for helping with the release and tuning the human material weights.
– Hans van der Zijden, for going anywhere and everywhere to operate and represent Rybka, for proudly wearing whatever “medals” tournament organizers foist on him, and for staying out of trouble.
– Dadi Jonsson, for hosting the Rybka forum – the best forum I have seen on the internet – and giving Felix something to keep free from marauding bandits.
– Steinar H. Gunderson for Microwine, which allows Rybka to run on Linux despite my chaotic coding practices, allowing Felix to remain in the dark about the modern invention that is Windows.
– The Rybka 4 Beta testers for a fun, lively and productive Beta testing period: Majd Ansari, Wieland Belka, Shaun Brewer, Nick Carlin, Lukas Cimiotti, Jiri Dufek, Mathias Feist, Dadi Jonsson, Larry Kaufman, Felix Kling, Joachim Nettelbeck, Jeroen Noomen, Kostas Oreopoulos, Ulysses P., Teemu Pudas, Albert Silver, Shahar Tzafrir, Ernst Walet and Victor Zakharov.
– Mathias Feist, Matthias Wuellenweber and Frederic Friedel from ChessBase, for their organized, professional work, for showing me how a small business should be run, and for putting up with my learning curve on release issues.
– Victor Zakharov, Sergey Abramov and their team from Convekta, for their great enthusiasm, energy and creativity, and for having no fear of the impossible
– Nelson Hernandez, for a professional-quality video interview, complete with interesting background noises, and for provoking me into all sorts of predictions and statements which have so far not come even remotely close to being realized.
– Alan Sassler, for walking me through the arcane issues involved in tuning highly correlated feature sets.
– Shahar Tzafrir, for making sure that our cluster has a tough opponent.
– Rybka forum regulars, for all kinds of ideas, and for making sure I keep my feet on the ground.
– For anyone I may have accidentally left out.
– And, saving the best for last, to Iweta, for being great!
I’ll keep the details a surprise, but we’ll have a very cool announcement within two weeks.
I like the Asymmetrical Piece Scoring option. Tuning this option properly, I believe, is going to produce some very neat games. Can’t wait to see the results