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Chess Game Analysis
Using ChessBase Engines
(Part Two)

by Steve Lopez

The name "Blundercheck" connotes that the program will only show you major mistakes, but this is not the case. This analysis mode was originally conceived as a way for advanced players to check their own analysis; for example a chess writer could annotate a game and use "Blundercheck" to show any errors in his variations as a means of "double-checking" his work for "blunders" in his analysis. But "Blundercheck" is much more useful as a means for average players to get a more precise idea of what the chess engine is showing them.

Let's first illustrate how to set up and use the "Blundercheck" function, then we'll descibe the engine's output. Just as in the previous article for "Full Analysis", we'll follow similar initial steps to get to the "Blundercheck" dialogue. After launching your ChessProgram interface, hit F3 and select the chess engine you want to use for analysis. After selecting the engine, hit F12 to open the game list window. If the proper database isn't displayed, go to the File menu and select Open/Database and use the File Select dialogue to navigate to the proper folder and database file. Double-click on the file name to open the database.

After the list of games is displayed, single-click on the game you wish to analyze; this will place the black cursor bar over that entry in the game list. Now go to the Tools menu, select "Analysis" and then "Blundercheck" to display the following dialogue:
 

Some portions of this dialogue will be familiar to you (after you've read Part One of this series). We've already discussed "Side to analyze" but I'll again repeat my strong recommendation to always use "Both" -- the program works much better in this mode and it will also alert you to mistakes which your opponent made (and which you could have punished).

"Storage" was also discussed in the previous article.

"Output" is a new feature unique to the "Blundercheck" function. "Annotate as text" means that the lines of play the chess engine recommends will be presented as text annotations -- that is, they will appear strictly as text and will not be automatically replayable on the chessboard when you review the game. Consequently I strongly recommend the other option: "Annotate as variations". This will cause the chess engine's recommended lines to be presented as replayable variations (as they appear when you use "Full Analysis") -- you'll be able to play the variations on the chessboard when you review the game later.

The "Time" setting is the same as "Calc. time" in "Full Analysis" mode and the same recommendations apply here. An optional setting here is "Depth"; the engine will always analyze to the ply depth which you set in this box -- never less, never more. The "Time" and "Depth" settings are mutually exclusive, you can set one or the other, but never both. My recommendation is to use the "Time" setting instead of "Depth"; using the latter will often result in shorter variations which get truncated during "forcing" lines (such as in a series of checks or captures).

"Threshold" works in "Blundercheck" mode exactly as it does in "Full Analysis" and the same recommendations apply here.

A series of check boxes follows "Threshold" and gives you a good bit of latitude in how the chess engine will display its output. "Write full variations" is an interesting tweak. Checking this box means that the chess engine will display a complete variation (with moves for both sides) when it finds an improvement over what you or your opponent actually played in your game. If you uncheck this box, the program will display only the initial move when it finds something better than the actual play. Seeing just the first move isn't terribly beneficial to the average player; you'll often find yourself asking "Why was that a better move?" Consequently, I encourage you to keep this box checked so that you'll see the "followup" moves to that better initial move.

"Erase old annotations" works as it does in "Full Analysis" and applies to previously-annotated games; the program will remove any prior annotations from the gamescore.

"Training" was described in the previous article; it enables the program to generate timed training questions as part of its analysis. This will typically occur approximately every twenty to twenty-four games on average.

"Store evaluation" should definitely be checked: it allows the program to add its numerical evaluations to the variations it inserts into the gamescore. Unchecking this box actually defeats the whole purpose of the "Blundercheck" function for the average player. The option to omit these numerical evaluations is included primarily for grandmaster-level players who are presumably able to make these evaluations on their own.

"Check main line" tells the program to evaluate the moves that were actually played in the game by the two players. This should always be checked. The box for "Check variations" is for players who wish to have the chess engine "double-check" any variations they've manually added to the gamescore; this box is useful for writers/annotators who wish to have the engine check their work for mistakes.

After you've set your parameters in this dialogue, click "OK". The program will switch to the main chessboard screen, jump to the last move of the game (as described in the previous article), and start analyzing. It will step backwards through the game, adding variations and numerical analysis at the points where it finds a better line of play. When the program has finished analyzing the game it will return to the game list screen where you'll see the game again highlighted with a black cursor bar. You can now double-click on this game to load it and see the analyzed game:
 

Notice that Fritz6 (the chess engine used to analyze this particular game) has inserted variations at five points in the game at which it found a better move for either player (based on the "Threshold" setting provided when the analysis parameters were set). It's interesting to note the only text annotation provided: "Last book move". This means that 4.Be2 was the last move which was found in the opening book which was loaded at the time the analysis was started. Black's reply, 4...a6, was not found in the opening book.

To understand the chess engine's numerical analysis, let's take a closer look at one of the variations it provided:

The analysis is in reference to Black's seventeenth move (17...exd5). The numerical analysis is always given from White's point of view; positive numbers mean that the position is favorable for White, while negative numbers mean that the position was better for Black. In this case we see that White enjoyed an advantage of 94/100ths of a pawn (0.94) after Black's actual move of 17...exd5, meaning that White is almost a full pawn ahead in the opinion of the chess engine. But Black could have improved on this by playing 17...Bxc3. The program goes on to give a recommended variation in which it assumes best play for both sides. After this sequence of moves, which ends with 22.Qc4, White would still have enjoyed an advantage of 44/100ths of a pawn -- but note that this advantage is much less than after the actual game move. With 17...Bxc3, White was almost a full pawn ahead, but in the variation following 17...Bxc3, White's advantage would have been less than half a pawn. Black would have reduced White's advantage by exactly a half-pawn (0.94 - 0.44 = 0.50) had he played the Bishop capture instead.

The number "13" following the variation's numerical assessment tells us how deep the search went before the chess engine arrived at the given evaluation. In this case, the engine analyzed the position after 17.d5 to a depth of thirteen plies (half-moves) to come to its conclusion on how Black might have bettered his play.

We can easily see how precise this information is when compared to the output of "Full Analysis". While "Full Analysis" is a bit more readable, "Blundercheck" gives us more exact information. We know exactly how much better the suggested variation is when compared to the move actually played, and we also know exactly how deep the engine searched to arrive at its evaluation. Consequently, "Full Analysis" is well-suited to beginning or inexperienced players, while intermediate to advanced players will enjoy and benefit from the precision analysis provided by "Blundercheck".

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