by Steve Lopez

In last week's ETN we examined the "Full analysis" feature, in which Fritz6 analyzes a game and points out better lines of play accompanied by some text comments. But some of us who have been around chessplaying software for a long time are actually more comfortable with numerical analysis, in which a program provides its "commentary" in precise numerical terms. How does one get that "old style" analysis out of Fritz6?

The answer is "Blunder check", one of the hidden gems of the Fritz6 program. Fritz' documentation (going back to Fritz5) gives the impression that Blunder check is a tool designed primarily for chess annotators who want to have a software program check their work and point out errors in their analyses. While this is certainly a viable use for the feature, the average player will also find the feature quite useful for analyzing complete games.

As we saw in last week's ETN, the best way to access an analysis mode is to do it from the database (game list) window in Fritz6. This is because the program won't automatically store its analysis into a database if you acess the feature from the main chessboard screen. To start the Blunder check analysis feature, go to the database window, highlight the game you wish Fritz6 to analyze (by single-clicking on the game in the game list), go to the Tools menu, select "Analysis" and then "Blunder check". You'll see the following dialogue appear:

This dialogue lets you set the parameters under which Blunder check will operate.

The first things you should look at are "Time" and Depth". The "Time" setting was discussed in some detail in last week's ETN. The "Depth" setting warrants a bit of discussion. Forgive me for plagiarizing myself, but the following paragraph is lifted verbatim from my ETN column for November 21, 1999:

If you select "Depth", try to be reasonable about what you choose. Even on the fastest available PC hardware, it's not likely that the program will go past 15 plies (and this is with a fairly long search -- 20 to 30 minutes per move). If you have a Pentium II 11 or 13 are good values to use in this field. Always use an odd number -- this will help to avoid tactical oversights by making the program always consider the opponent's reply. Using an even number causes the program to sometimes be blind to possible responses.

I'm usually asked about my personal preferences via e-mail after these discussions. I prefer to use the "Time" setting, rather than "Depth". This results in deeper searches in simpler positions. I'm not saying that this is the absolute right way to do it -- I'm just saying that this is what I use. As always, your mileage may vary.

Plesase note that "Time: and "Depth" are mutually exclusive. You can select one or the other, but not both. "Depth" means that Fritz will always analyze out to the fixed depth that you have selected regardless of how much time it takes. "Time" means that Fritz will analyze for the amount of time you set (and usually longer, as discussed last week), regardless of the depth it reaches.

The "threshold" setting works exactly as it does in "Full analysis"; see last week's ETN for details.

"Storage" is also exactly the same as in "Full analysis"; again, see last week's ETN. "Side to analyze" is self-explanatory.

"Output" lets you determine the way Fritz6's analysis should be displayed. If you're having the program analyze a previously unannotated game, choose "Annotate as variations". This means that Fritz6's analysis will be displayed as replayable variations in the game (you'll be able to play through the moves on the chessboard just as you would with an annotated game from the database). However, you may be having Fritz double-check your own (or someone else's) variations that have been entered into the game. In this case, Fritz6's analysis may become "buried" as sub-variations in a mass of analysis and annotation lines. If you select "Annotate as text", Fritz' suggestions will appear as annotations (similar to what you could type in the annotation window) rather than as replayable variations.

There are a number of check boxes in this dialogue. Checking "Write full variations" means that Fritz will provide you with entire variations in its analysis. Unchecking this box means that Fritz will show you just the first move of the variation.

"Erase old annotations" means exactly what it says. If the game has been previously annotated, Fritz will remove the old variations and text annotations and replace them with its own notes. The best way to use this box is to check it and make sure you have "Append" selected under "Storage'. Fritz will then strip the old annotations, insert its own variations, and then add the results as a new game to the database and leave the original annotated game untouched. If you uncheck the "Erase old annotations" box and select "Replace" as the storage mode, you'll be able to see Fritz' commentary side by side with the original annotator's notes in the same game.

"Training" allows Fritz to create and insert timed training questions as described in last week's ETN.

Finally, there are two boxes for "Check main line" and "Check variations". You can select either one of both of these options. Obviously, it makes no sense to select "check variations" if there are no pre-existing variations in the game. However, if you want to have Fritz double-check variations that you or another annotator have inserted in the game, you'll want to check this box. If the game is not previously annotated, use "Check main line".

Once you've set your parameters, click "OK" and Fritz will begin to analyze the game. As stated in last week's ETN, this is a process that's best left to run overnight. The program will begin its analysis with the last move of the game (for reasons which were also discussed last week).

When Fritz is finished with its analysis, it will return the display to the game list. When you double-click on a game to view it, you'll see Fritz' analysis displayed on the screen. Here's a sample move from a game which was analyzed with "Annotate as variations" and "Write full variations" selected:

Fritz has evaluated the actual position as being better for Black by 12/100ths of a pawn (this is what the entry "-0.12" signifies. If the number is positive, it's an advantage for White; if it's negative, it means the advantage is Black's). But Fritz has supplied me with a better line of play. Had these moves been played (and it assumes best play for both sides in Fritz' opinion), Black would have had an advantage of over a half-pawn (-0.53) in the position at the end of the variation. The "/11" tells me that Fritz did an eleven-ply search to come up with this evaluation.

This type of numeric analysis is exactly why I referred to "blunder check" last week as a more precise means of analysis than the "full analysis" option. We not only see a better line of play, but we know exactly how much better the variation is, down to 1/100th of a pawn. For many beginners this is essentially the same as splitting hairs, but I personally think that it's invaluable information for the intermediate to advanced player.

We now know how to get this analysis, but how to we interpret it and use it to improve our playing? That's what we'll look at in next week's ETN. Until then, have fun!

You can e-mail me with your comments, suggestions, and analysis for Electronic T-Notes. If you love gambits and sacrificial play, stop by my Chess Kamikaze Home Page and the Yahoo Chess Kamikazes Club.