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The answer is called the Shootout mode; it's a means of getting a chess engine to play a game (or series of games) against itself. You can cause the games to begin from the standard chess starting position, but then the software doesn't use an opening book. Shootout is best used when playing from a position at some point later in the game. You might start it from one of those positions which opening manuals evaluate as "unclear". Maybe it's just a position you saw in a game and found interesting. It might even be a position from one of your own games in which you were a bit befuddled at the time and wonder how a chess program might play from that position.
For an example, we'll start from a position from a database game I was playing through. This is a game from 1851 (yeah, I'm a sucker for those old classical games) in which a fellow named Alfred Brodie had the White pieces against the legendary Howard Staunton:
Staunton has just played 22...Ne4; he enjoys a space advantage and his pieces are better coordinated than are White's (the positioning of the two White Rooks is just ugly). I know how this game ends (Black wins) but I'm interested in seeing if White can extricate himself and save the game, assuming best play for both sides ("best" in the opinion of powerful chess engine, that is).
Let's have Fritz11 play a game against itself in Shootout mode, starting from the above position. I've loaded the Brodie-Staunton game from the database and clicked on 22...Ne4 to jump to that position. Going to Fritz' Tools menu, I select "Analysis", and then "Shootout" from the submenu to get to the following dialogue:
It looks like there's a lot to this dialogue, but it's really pretty simple when you break it down into component elements. You're going to do two things with this dialogue: set up how many chess engines you want to use, and tell the program what time controls you'd like the engine(s) to follow.
We'll start with a simple Shootout configuration: we'll have a single engine play a short series of games against itself. The "New" and "Delete" buttons let you choose which engine you want to use. Clicking "New" brings up the familiar scrolling Engine selector dialogue (the same as you get when you hit F3 from the main chessboard screen); single-click on the name of the engine you wish to use, then click "OK" to see it appear in the lefthand box (in the above illustration, I've already selected Fritz11). Note that the engine selector lets you choose the engine, the hashtable size, and any configurable engine parameters.
If you select an engine and then change your mind, highlight the engine in the lefthand box (just as you see in the above illustration) and then click the "Delete" button. Note that this does not permanently delete the engine from your hard drive; it just removes the engine from the shootout list.
Now we can select time controls. If you wish to have the engine play a single game against itself using the familiar "Blitz game" or "Long game" time controls, just click the proper radio button in the upper right of the Shootout dialogue. Clicking one of these two radio buttons will bring up the dialogue for that selected time control, and you can set the parameters as you choose (just as you do when you're setting a time control for a game you're playing against the software). Click the "OK" button and Fritz11 will then play a game against itself using the time controls you've chosen.
The third option is "Fixed depth". Let's say we select this option and type a pair of sevens into the "Depth" boxes (just as you see in the illustration above); this means that the program will start a game against itself with a move being made after the engine completes a seven ply search. Using our example position (after 22...Ne4), Fritz11 will calculate a move for White out to a seven ply search depth, then make that move. Then it will calculate a reply for Black; after the seventh ply is completed, it will make a Black move, then continue alternating sides and moving until the game concludes. In short, "Blitz game" and "Long game" use time as a limitation on how long the engine will think, while "Fixed depth" will use the "lookahead" depth to determine when the engine should make a move.
The maximum length of the game is determined by the value entered in the "Move limit" box. Unless you have some reason for truncating the game (you're interested in the course of the middlegame and don't much care about endgame play), you should leave this value set to the default of "999". When one considers that the longest chess game in tournament history was less than 300 moves long, the default setting should be sufficient.
I said earlier that you could have the engine play a series of games against itself. Consider the dialogue below:
By setting the "Depth" values to "7" and "11" (and checking the "Skip Even Plies" box), we see "= 3 Games" appear to the right of the "Depth" settings. What this indicates is that Fritz11 will play three games against itself. In the first game, moves will be made after a seven ply search. In the second game the engine will move after a nine ply search, while in the third game a move will be made after an eleven ply search depth is reached. Thus a series of three games will be played starting from the position after 22...Ne4, with each succesive game using a deeper search.
Note that if "Skip Even Plies" had been left unchecked, a total of five games would have been played, one at a seven ply search depth, one at eight plies, and so on through eleven plies. Why would you wish to skip even-numbered ply depths? Some chess engines (especially older ones) exhibit a form of tactical "blindness" at searches which are cut off after an even number of plies, which can artificially influence the results of such games. The dialogue gives you the option of skipping these even-numbered search depths.
After you've set the desired parameters, click "OK" and the engine you've selected will begin to play against itself. When the selected number of games are completed, you'll see a "results" dialogue appear:
This will give you the result of each game (identified by the ply depth used by the engine). The games themselves will be viewable by hitting F12 (to go to the Database window) and opening the Shootout database located at C:\Documents and Settings\[user name]\My Documents\ChessBase\Compbase\Shootout.cbh (more easily reached by the pulldown menu just above the game list on the upper righthand side).
I also mentioned earlier that you could have several engines play against themselves in a series of Shootout games. All you need do is add engines to the list in the initial Shootout dialogue:
In this case we've selected three engines; consequently we see that the dialogue indicates that nine games will be played. Each engine will play a total of three games against itself, one game each at seven, nine, and eleven plies. Three engines times three games each equals a total of nine games.
Note, too, that I've selected some low ply depths for the sake of our examples; it took Fritz11 less than three minutes to play the three games at the indicated search depths. Current computer hardware will allow you to play series of games with search depths comfortably in the teens without taking an undue amount of time. As always, you should experiment by trying different settings until you find ones that best suit your needs.
Until next week, have fun!
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