ELECTRONIC T-NOTES


CHESSBASE USA'S WEEKLY ON-LINE NEWSLETTER


FOR THE WEEK OF MARCH 7, 1999


ENGINE PARAMETERS IN FRITZ5.32

by Steve Lopez

There are a few ways to tweak Fritz' playing style. In addition to the sliders in Handicap and Fun mode, there are methods by which you can influence the engine's style of play directly. This week, we'll take a look at these parameters.

To activate the "Engine parameters" window in Fritz5.32, select it from the Levels menu.

AGGRESSIVENESS

This is the easiest one to understand. I still recall the first time I played Fritz2. It was the most aggressive chess program I'd ever seen -- frighteningly so, in fact. It just came at you relentlessly. I'd never seen anything like it. Looking back, I really wish that Fritz2 had contained a tweakable aggressiveness parameter back then. I'd have loved to turn such a parameter down a notch or two.

The "aggressiveness" parameter has five settings which range from -2 to 2. The higher the number, the more aggressively Fritz will play. Conversely, a setting of -2 will cause Fritz to play fairly passively (did I hear someone mention Petrosian?). The default value is 0 (exactly in the center of the range).

CONTEMPT VALUE

This adjusts how willing Fritz will be to accept a draw when playing against you. The value in the box is given in centipawns (1/100ths of a pawn).

For example, if you set the contempt value for a negative number, Fritz will tend to avoid draws. With a setting of -200, Fritz will avoid draws and play for a win, even if it's losing, until it's evaluation shows it to be behind by more than two pawns. In other words, Fritz becomes very haughty and arrogant, believing that it is a much better player than you ("I am the great Octopovich! You dare to try to make draw with me? I laugh in your face, you contemptible lower aquatic creature! Play on until I am to be truly crushing you!").

On the other hand, setting it for a positive number will cause Fritz to accept draws readily, even if it thinks it's winning. A setting of +150 will cause Fritz to accept a draw even if it's winning by a value of 1.5 pawns or less. Fritz becomes fearful that you will crush it later, even though it is winning ("I have heard men speak of you -- you are the legendary minnow who plays like a shark -- the guppy with no name! My intestines are filled with fear in your presence -- if course I will make draw with you!").

Keep in mind that these settings control a general tendency, that Fritz will not always accept a draw even with a large positive contempt value set. But you will see a difference over the course of several games. the default value for this feature is 15.

SELECTIVITY

Fritz analyzes literally thousands of moves a second. Selectivity lets you direct Fritz' tendencies in "aiming its firepower". Will it do a "broad" search (looking at everything in a given ply, rather than cutting out weak moves early in its search) or will it do a "deep" search (looking at just a handful of initial moves, but analyzing the consequences very deeply)?

This is a pretty important factor with chess computers. Here's what I wrote about selectivity back in 1994:

Rather than calculating all legal moves in a position (a very time-consuming task), they concentrate on a narrower choice of likely continuations. This has the effect of reducing the number of lines and positions to be evaluated and leads to much deeper searches. A drawback to narrower (but deeper) searches is that the program might miss something important because the line of play or position was not included in the tree of "most interesting" or "most likely" moves.

The range of values for "selectivity" runs from 0 to 6. Setting a high selectivity value will allow Fritz to perform very deep searches (but at the risk of missing something important that wasn't included in its narrow search). A lower value means that Fritz will consider many more lines of play, but because it's not cutting bad lines out of the search tree, it's not going to analyze nearly as many plies deep.

The default value for selectivity is 2.

There are, of course, some engine parameters for the other engines that are usable within the Fritz interface, but I'll save those for another time. Until next week, have fun!

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