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Game Analysis with Rybka Aquarium 27 November 2008
Aquarium’s Game Analysis
Aquarium’s Game Analysis is an advanced analysis method which performs an automatic analysis of one or more chess games from a database.
In most chess GUIs, game analysis is a simple process where a chess engine analyzes each position for a fixed length of time. If a better move is found, its evaluation is compared to the evaluation of the played move. If the improvement exceeds a predefined value, the engine variation and evaluations are added to the game notation. Aquarium’s Game Analysis uses a more advanced, dynamic approach, consisting of several stages.
First, Aquarium scans the whole game quickly to get a bird’s eye view of how it developed. If one of the players had a completely winning advantage in the final moves of the game, those moves will not be analyzed further. The same applies to the opening moves of the game which are instead annotated with reference games, human evaluations and stored engine evaluations.
After selecting the positions which will be analyzed further, Aquarium analyzes each of them more deeply. They are analyzed for the same length of time – calculated from the analysis time specified by the user and the number of positions.
In the next phase, Aquarium goes to work on the most interesting parts of the game. It digs into the improvements suggested in the previous phase using auto-play, leading to a more reliable assessment. In case there are many blunders the most important ones are assigned a higher priority.
Prioritization and other decisions related to the analysis are based on so-called mini-max evaluations that come from iterative deepening and the analysis of whole variations instead of single positions. Consequently, some mistakes that appeared to be minor during initial analysis may turn out to be major blunders after deeper analysis and vice verca. This unique feature of Aquarium’s Game Analysis sets it apart from other implementations.
In the final phase, Aquarium inserts the results of the analysis into the game as variations and evaluations. The user can choose settings which affect the annotations, such as the number of variations added to the game. If the number is set to a low value, only the most important blunders will be annotated. Otherwise all of them will be annotated.
One interesting feature of Game Analysis is the annotation of “tempting” moves which actually are blunders. Let’s say that a player had a chance to capture a piece with a pawn but didn’t do so. If the capture would have been a mistake, Aquarium will show the capturing move (with a “?”) and the variation that refutes the move.
The variations produced by chess engines can be quite long and the first moves of the variation are usually more accurate than later moves. The Untrusted engine halfmoves specifies how many moves should be cut off the end of the engine variations.
The number of variations that Game Analysis adds to the notation will never exceed Maximum total variations. Setting it to zero allows Game Analysis to decide how many variations will be added.
You can use the default database as shown here, or any other CDP database. This allows you great flexibility in controlling what type of games are referenced. You could, for instance, use a database of recent games by top players. If you are analyzing and publishing games from an ongoing tournament you might want to add games by the participants to the database. This could be games played previously as well as games played in the tournament itself. Finally, if you are analyzing a local tournament it might be interesting to have games played by local players in the database.
One of Aquarium’s unique features is that it saves all its analysis to disk. This means that your analysis isn’t lost even if you accidentally turn off your computer while Game Analysis is running. When you resume the analysis, it continues from where it left off. In some cases, however, you may want to repeat the analysis and discard previous results. In that case select “Discard previous analysis”.
The Results of Game Analysis
CAP evaluations. Aquarium comes with two analysis trees, containing previously analyzed positions, mostly from the opening phase. The smaller one contains 20 million positions analyzed by Rybka and the bigger one has 44 million positions analyzed by Rybka as well as other engines. You can see examples of evaluations coming from the Rybka tree after White’s 5 th and 7 th move as well as the final CAP evaluation, which comes after White’s 9 th move and is marked with ‘CAP’.
Reference games. As was mentioned above you can specify a database which Aquarium will use to add one or more reference games to the opening (Opening database CDP in the Game analysis settings). An example is shown above after White’s 7 th move, where a game fragment between Malaniuk and Ivanchuk has been inserted.
Novelty. Aquarium searches for two types of novelties. The first uses a tree created from HugeBase (Atrees\statistics\d2m). In the game above 9…a6 is a novelty which was not found in the tree. The second one uses the opening database from which the reference games are taken. The move 7.Nxd4 was not found in the database, so it is marked with an ‘N’ and a reference game follows. Note that if I had chosen HugeBase as a referrence database, there would be only one ‘N’ as the tree is built from that database. In that case Aquarium would inserted a different game after 9…a6, probably played by much lower rated players. Another idea is to use a database with your own games. In that case you would immediately see where the game deviates from your own, and how your game continued at that point.
Game Analysis is a valuable addition to other analysis tools available in Aquarium. It’s fully automatic so you can let it run overnight and have the completed analysis available in the morning. It gives detailed information about all phases of the game and its advanced analysis method means that it’s more likely to give a realistic assessment of the game.
Major update to Aquarium
I recommend that you check out the new Aquarium version 3.07, which is a major update. It’s free for existing customers and adds new features such as greatly enhanced database handling, printing and exporting (including web publishing). All the new features are explained in the Aquarium FAQ.
The update can be downloaded through the ChessOK Downloader. For further information see the announcement on the Aquarium support forum.
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