Engine styles and ponder hit

[Kirill Kryukov]

I just had one idea. Often people ask "What engines have interesting style?". I was thinking about how to define "interesting engine" and thought it must be different from the other engines, especially those of its own strength. So, theoretically, any similarity (or difference) measured between engines can be used to discuss "interesting style". So I thought that our "Ponder hit" statistics can be utilized for something useful at last.

For this example I selected a set of well tested engines in CCRL 40/4 (most of which I tested myself too). "Well tested" here means not only large number of games, but large number of games with the other members in the same group of engines.

Ponder hit table for my selection.

Ponder hit has color background which allows to visually read the table (unless you changed the background colors in your browser). More orange color means more different pair of engines (lower ponder hit), and more green or blue means two engines are similar (higher ponder hit).

Checking the table visually, you can easily recognize some engines which have mostly green/blue cells in their row, and also those which have mostly orange. My hypothesis is: engines with many green/blue colors have "usual", "common", "uninteresting" style. And engines that have many orange colors in their row have "unusual", "fresh", "interesting" style.

Some particularly "common style" engines that I recognized:

• Fritz 5 and 6
• Petir 4.72
• Ktulu 4.2
• Slow Chess Blitz WV2.1
• Pseudo 0.7c
• Delfi 5.1

And here are some of the "unusual style" or "interesting" engines:

• Chess Tiger 2007.1
• The Baron 1.8.1
• Jonny 2.83 32-bit
• Smarthink 0.17a
• Little Goliath Evolution 3.12
• Trace 1.37a

These "interesting" engines have many orange colored cells, which means they have low ponder hit with many opponents, which means they "think different".

What do you think about this logic? Does it make any sense? How does it correlate with your own understanding of those engines? Any comments are welcome.

[Tony Thomas]

The once that you mentioned as having an unusual style, namely CT, LG, and The baron are recognized by many as interesting engines. So I guess it is a good start after all.