PeSTO: Piece Square Tables Only

Right now PeSTO is participating in the Qualification League of TCEC S17. PeSTO is an “experimental” chess engine in that it has only minimal chess knowledge in it’s evaluation and that it depends on the AB search as much as possible as opposed to the recent development of Neural Network engines which rely foremost on complex learned chess knowledge.

The most elementary chess knowledge is the relative value of the chess pieces. Playing with only that knowledge is (still?) not enough to let PeSTO play reasonably good chess, although it performs very good in tactical testsuites like WAC. It also needs some elementary positional knowledge to play reasonable chess. The simplest form of positional knowledge are Piece Square Tables (PST), in which a value is assigned to every square on the board for every piece. A higher value for the square means a general better position for that piece.

The values change during the course of the game. In the beginning of the game it’s better for the king to stay on his own border of the board, in the endgame the king should be away from it’s own border. That’s why there are 2 PST for each piece, one for the opening and one for the endgame. Depending on how many pieces are left on the board the values between opening and endgame are interpolated accordingly (so called tapered evaluation). In addition to the piece values and PST there is a tempo bonus for the side to move, and that’s it, no other chess knowledge is present in PeSTO.

PeSTO uses different tables than rofChade and also has some search tweaks (most important less aggressive LMR due to worse move ordering). The tables are tuned with the Texel tuning method.

If you want to use PeSTO, you can download it in the download section.

New rofChade released: version 2.202

This release is mainly a bugfix of release 2.2, it also contains a LMR tweak which will add around 10 elo.

The bug: When the search was pondering or in infinite analysis mode, sometimes the search would return a “bestmove” prematurely. This is not correct and some GUI’s can not cope with this bug and crash (for instance the Shredder GUI).

A big thanks to Gerhard of the cegt team for noticing the bug and helping to find the cause! and a big thanks to all who take interest in rofChade.

New rofChade released: version 2.2

After a longer period of little activity I got a boost to develop a new rofChade version after trying a retune with the “lichess-good” set as discussed in the topic about Texel tuning viewtopic.php?f=7&t=71469#p807692, I got an elo increase of around 30 elo! So thanks Fabian, Jon and Vivien for discussing the topic and making the position set available!

Version 2.2 also contains multiple changes which resulted in an estimated elo gain of 50/70 elo single threaded. Because of some changes to hash table and multi threading the elo gain with multiple threads is hopefully a bit higher.

rofChade 2.2 can be downloaded under the tab “Download”. Under the tab “Releases” the version changes are defined.

Thanks to everybody who takes interest in rofChade!

New rofChade released: version 2.1

There is a new “official” release available of rofChade, version 2.1. Between version 2.0 and 2.1 multiple intermediate versions have been participating in different tournaments (TCEC, CCC, International GSEI web tournament, Swiss tournament and Graham’s Amateur Series).

In addition to multiple search optimizations, version 2.1 also contains syzygy Tablebase support via the fathom library. All the changes of version 2.1 are shown under the release tab.

A special thanks go to Ronald de Man, Basil Falcinelli and Jon Dart for making the implementation of endgame Tablebases (syzygy) a breeze, and to all the testers, who devote a lot of time in testing rofChade (and many other engines).

Finally, thanks to everybody who takes interest in rofChade!

New version with regular eval released: rofChade 2.0

A preliminary version of rofChade with regular evaluation terms has been participating in TCEC season 14, so it’s time to release an “official” version which is entitled version 2.0.

Version is a slightly enhanced version compared to the one that was competing at TCEC. For more details see the release page.

The Windows and Mac versions can be downloaded from the download page.