Convekta Logo
Chess Software Sourcebook
Join Chess Reviews<>
Convekta Logo
CAP Data - what it's for, how to use it
keywords: CAP, Corbit, Zakharov, Opening
Robert Pawlak
Friday, November 04, 2005
CAP data has been included with every version of CA since CA 5. It contains computer evaluations of millions of opening and endgame moves. Since CAP tells you when a move is good or bad, it can also alert you to the presence of an important theoretical novelty or refutation of existing theory. This is because CAP shows you not only its evaluation of the moves that have been played before, but of moves that have yet to be played as well.


CAP is short for the Computer Analysis Project, an effort started by Dann Corbit. CAP data consists of positional evaluations for many opening moves in the game (and some endgames as well). Currently, the only programs that use CAP data are Chess Assistant and Bookup. When you buy any version of Chess Assistant, you get the CAP data as well, there is no extra cost.

CAP data has been integrated into the tree display in every recent version of CA, and is now also used in other areas of the program as well. For instance, it is employed in the automatic opening commenting and game analysis functions, and can be used when constructing opening books as well. This article will focus on the use of CAP when conducting opening study.

The CAP data is held in the CAP tree, which is installed by default with every version of CA since CA 5. By default, when you examine a game in CA, CAP data is shown for every position in the game, and appears below the game score.

[CAP tree]Let's look at what the CAP data tells us after the following moves: 1.e4 c5 2.Nc3 Nc6. The resulting tree display is shown to the right. You will note that there is a column labeled "CAP", with a bunch of numeric evaluations. These numbers give the computer's evaluation regarding the position. A positive value favors white, and a negative value favors black. A value of -1, for example, would mean that black is ahead by the equivalent of one pawn (due to positional or material factors). Likewise, a value of +3 would mean white is a piece ahead.

You will notice that there is a grey bar that divides the upper and lower parts of the tree display. The moves shown above the bar have all have a corresponding game in hugebase, which is the reference database used by Chess Assistant. Those below the grey bar have yet to be played, however, they have still been evaluated.

If we look at the tree display, we see that from CAP's viewpoint, 3. d4 (also, see pic below) simply drops a pawn for no compensation (according to computer analysis). However, that has not stopped some people from playing the move in six games contained in hugebase.

[CAP Progress]CAP data can also be shown in the game progress display. In some versions of CA, the game progress display is enabled by default, but in some it is not. To turn it on, go to the "Tools" menu, and select "Options", then click on the tab labeled "View". On the lower right hand corner of the dialog box, you should see a setting labeled "Game progress". Make sure it is checked. After you do this, every time you open a game, you will see a display of the computer's evaluation of the game progress in a graph below the board. As is shown to the right, the CAP data is represented by the blue bars you see on screen.

As we see from this unfortunate example, the bar graph can tell you where the game started to go south (in this case on move 3 for white. Incidentally, if you hold the mouse cursor over the progress display, you should see a tooltip that gives you the exact value of the CAP evaluation for a particular move.

CAP data is used in other parts of CA as well. For instance, when you have CA provide engine analysis for your games, you'll notice that there are spots for you to specify whether CAP data is used in the commenting process. Right now, the option only exists to use both CAP and eval (eval gives master evaluations of moves) at the same time. When you use one of these methods, you are telling CA to insert moves if the difference between the game and Eval/CAP evaluation differs by more than a specified number of symbols. For example, if the number of symbols difference for CAP is set to 1, CA will annotate games where say, it is white to move, and the evaluation changes from = to +/=. This function only works when the move in the game and an alternative move in the tree both have master evaluations.

[Comment opening button]

Another place CAP data is used is in the opening commenting function. This can be accessed by clicking on button with the question mark on the comments button bar (see right).  A complex set of algorithms is then used to combine CAP data and master evaluations to automatically comment the opening of your game (novelties will be shown as well). Give it a try, I think you'll find it is very useful.

CAP data can also be used when constructing opening books. However, this is beyond the scope of this article.

Additional Information on CAP (courtesy of Victor Zakharov)

At the time of this writing, the CAP project has been in existence for nearly five years. The total number of positions in the database currently stands at well over 12 million, and computers from all over the world have been used to obtain the evaluations that you see in the CAP tree. While much of the analysis has been provided by Crafty and Tiger, other engines (such as Rebel) have been used as well. Most positions in the tree have been evaluated using the equivalent of from 1-5 minutes on a 1 Ghz PC.

Currently, the CAP data takes up over 200MB of hard drive space, in CA's highly compressed proprietary format. Access to this data is instantaneous. Convekta maintains a central CAP server that can be used by CAP clients throughout the world, via a simple screen saver. However, the screen saver software has not been released yet, but could be, if there is enough interest from the public. The analogy that you should think of here is the SETI@home project or protein folding.


ChessAssistant is a trademark of ChessOK
Syndication available through rss.xml
Click on my name to send me e-mail (must have javascript on)