Computer Chess Club Archives




Subject: Testing the reliability of forward pruning

Author: Russell Reagan

Date: 15:17:09 05/15/03

I would like to know how to test whether or not a forward pruning method is

I have one idea to test when and if a method is reliable, and I'd like to know
if it's a good idea or not, and also what other methods might be used to test
the reliability of forward pruning methods.

My idea requires a collection of games, and two versions of a program. One
version would have forward pruning turned off, and the other would have it
turned on. You would feed each version of the program the same game, and let
each do a search on the initial position to the same fixed depth. If both
versions report the same move and score, and the version using forward pruning
had a lower time to depth, then the forward pruning is reliable (so far). If the
version using forward pruning reported different results, then the forward
pruning method is not reliable for this type of position. You make the next move
in the game, and repeat the search and compare the results for each position in
the game. Then you repeat the process for each game.

When I think about testing the reliability of null-move using this method, I
think the test would do well. I would expect the test to tell us that in most
positions, null-move is reliable, and I would expect it to fail for some endgame
positions, and so this test would tell us that null-move was good forward
pruning, but to turn it off in the endgame (or detect zugzwang, or however you
choose to guard against it). I haven't had time to test this though, since I
just thought of it and I'm not at home.

I am basing all of this on the assumption that the strength forward pruning
provides is not that it finds better moves at the same depth, but that it
finishes searching a particular depth in a shorter amount of time, allowing the
search to go deeper, which is where the added strength comes from. Is this

Comments, please...

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