"Modular" Chess Engines
(and What They'll Do for You)

by Steve Lopez

The fact is that nothing was overwritten at all and that the programs are behaving exactly as they should. Let's take a closer look at these modular chess engines and discover what's really happening.

I've been in the chess software business for a long time and I've learned that if a chess player owns one computer chess program, he's likely to own a half-dozen or more. I wouldn't exactly call it a "compulsion" or an "addiction", but it's true more often than not that a chess player will own more than one chess playing program. Owning (and using!) an assortment of chess programs is often very useful because different programs usually play in different ways. Additionally, various programs might have useful features which differed from each other. Back in the 1990's I regularly used a variety of chess programs produced by different companies because each program I used offered something useful which the others did not.

But the downside of owning multiple programs was that each of them had a different interface. A "graphic user interface" (or GUI) is a fancy term for everything you see on the screen while using a computer program: the menu items, the various displays, popups which appear when you right-click on something, dialogues which allow you to enter information or make a selection - all of these elements are part of the GUI. The fact that different programs had different GUIs was a bit of a grind. Everytime you purchased a new chess program, you had to learn a whole new interface. You had to figure out where features (like time controls or level settings) were located in the menus, you had to learn whether moving a piece was a "two-click" or a "drag and drop" process, and so on. All of that time you spent learning where everything was located could have been better spent in using the program to play and/or learn more about chess.

In the late 1990's, the ChessBase company hit on a simple (some might even say "obvious", hindsight being what it is) solution. If you could "unplug" the chessplaying portion of a program (the program's "brain" or engine) and "plug in" a different one, you could have the benefits of using multiple chess programs for play and analysis without the hassle of having to learn all of the features of a variety of interfaces. Everything on the screen would look the same (because it would actually be the same) - you'd just be swapping out one chess brain for another, much like changing a drill bit or a different sized socket on a wrench.

Ever since that time, this idea of "swappable" (i.e. modular) chess engines has been a standard feature of ChessBase products. The chess computing world took note of this and, in the decade since, has instituted a "standard format" for the programming of chess engines which allows further interchangability. This format, known as UCI, has also been introduced into ChessBase-produced software, allowing the user to download numerous free chess engines and use them within their playing programs.

What does this mean to you, the chess player? Owning different chess playing programs gives you an additional variety of opponents to play against; for example, one game you might want to try your hand against the tactical style of Junior, while you may want to play your next game against Shredder's rock-solid style. You simply change the chess engine between games, selecting the one you wish to play from a scrolling list within the program:

That same difference in playing styles is particularly important when different chess engines analyze games. You can set up your software to allow multiple chess engines to analyze the same game; you'll often discover that different engines offer different recommendations at the same point in a game - Fritz and Hiarcs might each offer a suggested variation which improves your position, but the variations themselves differ. They're both better moves or variations than what you actually played, but the two "opinions" differ on what that best move might have been (in just the same way that two grandmasters might disagree on the particulars of a given chess position).

Understanding the concept of a single GUI (user interface) which can run multiple chess engines is the key to understanding what happens after you've installed more than one ChessBase-produced playing program. For the sake of our example, we'll say that you've already purchased and installed Fritz 11 some time ago and that you're about to install the ChessBase version of Rybka 3.

You've spent the last few months using Fritz 11 and you've noticed certain things on your screen, things which are part of the GUI - the interface. For example, when you'd double-click on your Windows desktop icon for Fritz 11 to launch the program, you see the following splash screen:

After clicking "Play Fritz", various title bars and other dialogues in the GUI also make reference to "Fritz 11".

Then you purchase and install the ChessBase-produced version of Rybka 3. Now when you double-click your Fritz 11 desktop icon to launch the program, you see this splash screen:

...and you're suddenly surprised. "Wait a minute! Rybka just overwrote my Fritz!" might be your initial reaction.

Actually, no, not really. The splash screen and the various title bar references in the GUI are merely cosmetic; if you click "Play Rybka" and hit F3 within the main chesboard screen of the program, you'll see that your Fritz 11 engine is still available for use, as well as your new Rybka engines, plus any other engines you'd previously installed:

Here's a (slightly) technical explanation for what's going on. The user interface (the GUI, which we've previously discussed) is a program component which is separate from the chess "brain", the engine - these engines are removable and interchangable (instead of being "welded" into the program as was the case with chessplaying software back in the early/mid-1990's). The GUI is actually called "ChessProgram 11" and it consists of the chessboards, menu commands, etc., in short everything except the chess engines themselves. Both Fritz 11 and Rybka 3 use ChessProgram 11 as their user interface; the difference in the two DVDs is the engines themselves.

So you're still looking at the same program as before; the only difference is that the splash screen and a few title bars in the program say "Rybka 3" instead of "Fritz 11". Once you've launched the program you can hit F3 to load the "brains" of Fritz, Rybka, Crafty, or any other engines you've installed (Junior, Shredder, and Hiarcs included, as well as free UCI engines from the Internet, or even older engines such as Chess Tiger).

A few users I've talked to seem to be really bothered by this "change", even after they learn that there's no real difference other than the purely cosmetic one of the splash panel and minor screen changes. "Well, how do I change it back to say 'Fritz 11' the way it used to look?" they'll ask. Believe it or not, that's easy to do. When you'e in the main chessboard screen of the program, go to the Tools menu and select "Options" to bring up that dialogue. The top of this display has several "tabs" (like those on manila file folders); click on the "Version" tab:

In the "GUI Version" box, single-click the black arrow to drop down a menu of choices:

This will display all of the "ChessProgram 11" software you've previously installed. Click on your choice, click the "Apply" button, then click "OK" to close the "Options" dialogue. The next time you start the program, the splash screen and title bars will reflect the choice you've made.

Note that following this procedure does not change the chess engine itself! You'll still need to hit F3 (or go to the Engine menu and select "Change main engine") to "unplug" one engine and "plug in" another (as described earlier in this article).

Hopefully this article will ease your mind and relieve your panic when you install a additional ChessBase chess  playing program and see a different splash screen when you launch your program. Relax - the difference is strictly cosmetic and easily reversible (if you so choose).

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© 2009, Steven A. Lopez and ChessCentral. All rights reserved.

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