Author: Severi Salminen
Date: 00:46:26 01/06/01
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>If you are extended futility pruning only some moves in Search (and allowing >some through) your best score so far should be set by the best move that gets >through as normal. If only one move makes it through its the best move. Yes, that is clear. >If you are pruning ALL moves you think there are no winning moves at this >position. In this case you should fail low and return alpha. Note DO NOT just >return best score (which is probably set to -INFINITY)... I learned that from >experience -- it caused the nullmove mate threat extension to go nuts and >exploded the tree. My initial point was that could I find a better value than just alpha. Returning a lower value could improve the possible necessary researches - and hash score as you mentioned. >In a normal qsearch you compute a static eval score... test if its >= beta and >you can stand pat... If not set best score to the static eval with an assumption >like nullmove -- that there will be some move at this point that can improve (or >at least maintain) the score... some move should be better than no move at >all... Yes, I'm doing stand pat cutoffs. (Forgot to mention...) >When you are going to prune away the rest of (or all) the captures (because of >futility condition or because the SEE says they are losing) return the best >score thus far. > >If all moves were pruned this best score is the static eval of this node you >computed at the top. Ah, of course! Now I'm allways returning alpha, even if all moves were pruned and the standpat score is <alpha. In this case I should of course return the stand pat score. >>I ask this because PVS or aspiration window search doesn't seem to like "wrong >>values" > >I don't understand this. Well, I've had many interesting problems because figuring out what to return in these cases. Severi
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