Author: John Hendrikx
Date: 10:27:45 12/25/99
Go up one level in this thread
>>Now, I can think of the following four standard >>enhancements to a search function (there are >>probably some more): >>null move >>killer move >>extensions >>hash tables >I don't see 'capture moves'. They are _critical_ and have to be done >before any other move (except hash table move). As it happens, I've started playing around with move-ordering as well, and giving priority to captures increased the speed by a factor of 3 (I already made sure that the PV was the first move tried). I also found that trying pawn-moves (not captures) after all other moves gave me another nice speed up (about 30%). Currently I have this order: 1. PV 2. Captures (ANY captures -- no SEE algorithm involved (yet)) 3. Piece moves 4. Pawn moves No killer/history heuristic yet. I don't know if sorting Pawn Moves last will hold up in later stages of the game (I only tested the beginning) -- I could give Pawn Moves scores depending on how far up the board they are though... I've tried adding null-moves as well, but haven't been very succesful. I need some more to go on before I can get it right, but I can't find good examples or descriptions of them. So far what I've tried is to try a null-move before doing any real moves at a certain level of the tree, and searching the null-move to the same depth as usual; my problem is that I don't know what to do with the returned score. From what I gathered one should create a cut-off when the score is 'not so good' even while doing two moves in a row.. it didn't work for me though. It was far slower (1.5 times) with the same results, and only a few dozen null-move cutoffs at 6 plies orso. When I increased the cut-off point by half a pawn in favor of more null-move cut-offs all I got was a bunch of very bad moves. What can one reasonably expect to win if one is allowed 2 moves in a row? Should null-moves be tried for both black and white? >killers and history moves are similar. history is a more global concept, >while killers are more local to specific parts of the tree. I use both as >with killers you can try them before generating all the non-capture moves. >>If 1), how would you order the above in decreasing >>order of effectiveness? > >I do the following: > >1. hash table move Is that the same as the Principle Variation? >2. captures with expected material gain >= 0 (using the classic SEE approach >to determine expected material gain). moves are sorted by expected gain. >3. killer moves >4. 4 history moves >5. remainder of move list. John.
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