I wonder if the side to move bonus at the end of a long PV is really comparable to the side to move bonus in a given position.Don wrote:In my testing the side to move bonus has a positive affect on playing strength, even when you ignore tree size considerations. It's very small, but it is an improvement probably because it's a valid concept - given some random chess position it is better for it to be your turn to move 99% of the time.Jan Brouwer wrote:I agree for the general case, but for this bonus I think this method is valid.bob wrote:Here's what's wrong with the idea. If you infer that smaller trees are better, get rid of all extensions. And any eval term that produces really large positional score bonuses. The tree size will go down. In fact, if you get rid of your evaluation completely, you will search really compact trees. And for tactical positions, this will do better in terms of faster solutions and smaller trees, but the program won't exactly play very well...
I have seen literally hundreds of cases where an eval change makes the tree larger, about as many as I have seen where an eval change makes the tree smaller. I don't think this is a good way to choose eval parameters. At least IMHO.
Tree search space is a function of several variables. If your eval change can somehow eliminate some searching, you might get good results for tuning a value. But many terms do not make the tree smaller, but do make the program stronger.
It is such a simple feature, using only a single binary input, it is hard to see how it could have any influence on playing strength other than via tree size.
Perhaps a whole class of evaluation features can be found which can be optimized via tree sizes.
You could test this on your cluster, Bob, and provide those of us with more modest resources with a list of features we can actually tune
Hmm, I could actually test that myself I guess for those parameters in Crafty which have already been tuned...
Anyhow, if your testing indicates that the bonus improves strength even when compensating for tree size differences,
then maybe it is a sign of a systematic bias in quiescence search (given that most quiescence searches are very short), caused by the standing pat part?