Thursday, November 13, 2014

Computer chess

Today the internet provides us an abundance of information. If you follow Chessbase (and I don't mention on purpose Chessvibes, which after the acquisition by only remains a shadow of the initial site) then you know what I mean. There are not only the toptournaments which are successive but there are also national and local events, twic and many other blogs and sites. I forget the DVD's, chessmagazines, books which have some more or less some lasting value.

Currently the 7th season of TCEC is ongoing, and the games can be watched live. For people not yet familiar with TCEC, it is the unofficial WC for engines in tournament-chess. In the previous years this format earned credibility, the tournaments run smoothly and the site is exemplary. With the worldchampionship ahead (I wrote this article on 6-7th of November), it will be a difficult choice. In the previous WC between Anand and Carlen I did follow some games live (this was possible considering the time-difference with India as it was after office hours) and I really enjoyed it. Especially the game in which Carlsen in a rook-endgame sacrificed 2 pawns to challenge Anand with the advanced king and pawn made live a big impression. Running an engine in the background allows the kibitzer to easily understand the ongoing events. This is the big asset of live watching grandmaster-games.

Maybe some people will consider evaluating a position with a single number too simplistic for chess but for many modest players - and I am one of them- this evaluation plays the role of a grandmaster-commentator.
Recently - in fact still ongoing- I am following the 7th season of TCEC. We are now in stage 2 and I catch myself that I daily do a quick check how the ongoing game is folding out. The tournament is extremely strong - Carlsen would not have any chance as all engines are stronger than him. E.g. the average calculation-depth is 25-30 plies and it often happens that at the end of a main-line we have an endgame on the board, while the opening isn't finished yet. Another example: Chiron announced against Naum mate in 93 moves. It is not a record (in the Lomonosov database there are mate-sequences of more than 500 moves), but still it is impressive how deep chess-software gets. The fun part is that they play this time without real openings - engines have to invent theory themselves and try to achieve nice positions (engines better have to use some early middlegame-knowledge which otherwise is only necessary if the opponent leaves book early).

The 4 top-engines (Komodo, Stockfish, Houdini and newcomer Gull) have their own characteristics. Especially Komodo's analysis of his game against Houdini impressed me a lot.

Komodo sacrificed a pawn for permanent pressure on the whites position and you could notice that Houdini never would escape out of it unless returning the material. Here Komodo showed constantly a minimal plus for white (despite the pawn extra for white) and kept this evaluation stable( the position did not change during 30 moves). Houdini evaluated the positions bit differently, although nothing substantially changed. It was clear that Komode made a much more 'human' evaluation of the position and surpassed the pure calculations of (in this case useless) small advantages. In the end Komodo broke through. I don't really care if this had to do with a better evaluation or a better calculation. Anyway Komodo evaluated the position more accurate and therefore deservedly won the game. Such improvement is a big advantage for each player and this is exactly the main asset of using Komodo for analysis.

This was only 1 example in favor of Komodo. In Komodo - Protector, the engine punished superbly an inferior queen-move in the endgame ( I wonder if somebody like Carlsen or Caruana would notice such opportunity). At move 54 Protector plays Qd7 instead of the anticipated Qb8 by Komodo. What follows is a long line in which black gets out of balance (Komodo's evaluation raises to maximally 0,85) but the advantage is not large enough to win as insufficient material remains on the board. So immediately also a counter-example but nevertheless a very instructive and epic game.

A second remarkable aspect which I noticed for Komodo, is that the program starts to calculate faster when the game proceeds. No other engine shows such behavior. In the game against Houdini Komodo starts at 17.000 knps and finishes at 40.000 knps – Houdini stayed for a very long time just below 30.000 knps during the complete game. It seems Komodo is programmed in such way that the number of parameters to be calculated are decreased in the endgame without a negative impact on the playing-strength. If you add a very clever searching-algorithm (Komodo often calculates much deeper than the other engines which calculate faster) then apparently you have a top-engine. Often a new engine is promoted as indispensable or a big step forwards but in the last years we can count the game changers on one hand:Fruit, Rybka, Houdini and maybe now also Komodo. In a world in which we can easily analyze with free engines, it is maybe again worth buying Komodo.

Stockfish has become less extreme in his evaluation, but at the moment of writing Komodo was still the only engine unbeaten. I am a fan of Stockfish, if only because it is a freeware project - an example of the force of cooperation on the internet. Besides it was the first program considered as stronger than Houdini on the CCRL-site. Cheng (nbr 46 on the CCRL-list) almost lost childishly in their mutual game -only 34 moves which is a bit like grandmaster against amateur.

Houdini is a known force but we don't see any big improvements anymore. The engine made moderate progression since version 1.5 and misses the consistent small steps of improvement which the Komodo-team demonstrates already in several releases (late Don Daily mentioned before his dead that he still had several ideas to improve the engine). Nonetheless the engine still plays super-human and almost wins every time against weaker engines. An occasional loss against an almost equivalent opponent (Komodo, Chiron) seems to be the price which must be paid. If people think that on a level of +3000 that combinations are not possible and a win/loss is only bad programming, must surely replay the game Naum - Houdini in which Houdini plays the temporarily exchange-sacrifice 19...Rxb3. It wins the white queen for the 2 rooks, shatters the white pawns and finally picks them up one by one.

The 3 engines split the final places of the previous TCEC seasons - over their supremacy there is no discussion.

Gull is the new star - on CCRL40 (probably the most reliable reference for defining the strength of engines), it was already positioned at spot 4 - but here it seems to confirm. Some games it seems to win with luck but engine-chess exactly distinguishes from "human" chess that luck is absent (no bad day, no chess-blindness, no tiredness). Personally I don't know the engine well but it is surely has potential and maybe it can still bring surprises in the next steps (it is allowed to introduce a newer release in the later tournament-phases).

Junior is the number 5 - the program has a big collection of world-titles (although we can argue that some titles were obtained while not all top-engines were present). It also played a few fine games, in which his evaluation (which I always considered as very neutral - a bit like Komodo today) was often more accurate. A striking example was Junior-Chiron, in which the h-file (and the weak position of the black king) was of a higher importance than the 2 connected black pawns in the center.

Engine-chess boring? Well it won't be covered in detail in the chess-history but as it is represented on TCEC, it surely is enjoyable. And as all games are downloadable in the analysis-section (pretty redundant as the site already provides the service to replay them) it completes the fun. With this we arrived at the beginning: computer-chess-sites generate hundreds of extra games daily - games of a (very) high quality. Again an extra source to check materials for games ...


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