Author: Tord Romstad
Date: 13:55:49 12/28/03
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Hi Tom! On December 28, 2003 at 13:32:05, Tom Likens wrote: >Hello Everyone, > >I've been experimenting recently with using the evaluation function to shape >the search tree. Specifically, I've been using the static evaluation of >the current position and the previous position to determine if a move should >be extended or reduced. I also have been making allowances for moves that >increase or decrease the pressure against the king, attack hung pieces, >save hung pieces etc. That's precisely what I am doing in Gothmog, as you probably know. I'm glad to hear that you try similar ideas, and that your first results are promising. I've found that it takes lots of tuning and testing before it works well, but I think such techniques have great potential in the long run. If it's done right, most of the improvements you do in your evaluation function will automatically improve the accuracy of your search. >So far the results have been exciting, but also potentially frustrating. >The main problem I've encountered is that any pruning or extensions based on >the previous node's score cause hashing problems because this becomes path >dependent. In a way, I suppose this isn't much different then making these >type of decisions based on the value of alpha or beta as well, but these new >effects have (at least for my program) seemed more detrimental. > >My (obvious) question, how do other programmers deal with this phenomenon? >I suppose ignoring it is one option, but I'm hoping there is a better >solution. I agree that this problem is extremely annoying, and I have spent lots of time and effort trying to find a solution. Unfortunately, I still haven't found any good ideas. I asked a question about exactly this problem here in CCC just a couple of days ago, but the only person who replied was Dieter Bürssner, who also hadn't found a better solution than just ignoring the problem and hoping it wasn't too important. Tord
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