10.1.10.2 Defining move filters

The move filter allows you to control exactly how many moves GNU is examining at each ply. A ply is basically one move played by one side, thus if both sides played a move, it would be one whole move, but two plies, one for each side. To change the specific settings, press the Modify... button.

Although the predefined levels, such as World Class, Supremo, etc. are tested and good, you may want to know or control how GNU filters its moves to analyze and how many.

Move filter 1

[[movefilter1.png]]

If you are playing Expert level (this is what GGRaccoon is set at) or another 0-ply setting, the Move Filter settings will not change a thing, as Expert level automatically examines all moves. At Supremo level, this changes though, as it takes a selection of the best moves from 0-ply and examines them at 2-ply. This means that for those selected moves it will calculate all the possibilities 2 plies ahead and evaluate them, allowing it to find better moves. Since Supremo is a 2-ply setting, we are only interested in the 2-ply settings of Large as in the figure above. 3-ply or 4-ply settings will have no effect here because Supremo doesn't examine at that depth.

In the figure above, we can see it first will Always accept 0 moves. This first line means that it won't force any moves to be analyzed at 2-ply, it will only analyze moves according to the second line. If it had said it would always analyze 2 moves, this would mean that no matter how ridiculously bad the 2nd move was compared to the 1st, it would analyze both at 2-ply.

The second line says it will Add extra 16 moves within 0.320. This means that provided they aren't more than 0.320 equity worse than the top move, it will select a maximum of 16 moves to analyze at 2-ply. For example, in the figure below, the 2nd best move is no less than 0.453 equity worse than the top choice, so it didn't bother analyzing them at 2-ply as it is unlikely to change its mind on what the best move is.

Move filter 2

[[movefilter2.png]]

Take a look at next figure.

Move filter 3

[[movefilter3.png]]

Here, the exact same settings were maintained, but the 1-ply filter was activated. This just means that those 16 moves selected from the 0-ply are sent instead to be analyzed at 1-ply, and then up to 5 moves from 1-ply will be sent to be analyzed at 2-ply. So this would actually be faster than the previous setting (and weaker), since a maximum of only 5 moves would be analyzed at 2-ply depth.

Tip: Feel free to experiment with the settings, as you can always reset them by simply choosing one of the predefined levels. In order to see if they are better, or as good but faster, I'd suggest comparing the results with Supremo. One setting I have that works quite well, is to take the basic Supremo setting and in the Move filter reduce the 16 to 12. It cuts down on the thinking time by 20-25% more or less, and I haven't seen more than one case in over 10,000 moves where it missed the best move.