Author: Scott Gasch
Date: 12:47:25 07/02/04
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On July 02, 2004 at 08:23:46, David B Weller wrote: >1. should PVS kick in after 1st move, or after PV found as Bruce suggests on his >page? [I *think* tree is smaller Bruce's way] What do you mean by "kick in"? PVS means you search the first move with a window of alpha..beta in order to determine the score of that move. You then search moves 2..n with a minimal window on alpha. The assumption is that you already searched the best move first so every other move should fail low. If there is a better move out there (in the 2..n list) that move will fail high on your minimal window search and you have to open up the window and research it. >4. Fruit uses 'mate distance prunning' - I read in the archive [now down], >where some suggest using shallower mate score hash entries, and others suggest >boosting the 'draft' of mate scores [which is similar, I suppose] >Are these all different versions of the same thing? - any help? Hashing mate scores is tricky. The thing to realize is that when you have a mate in n score at a node it's relative to the root of the search. So if you have mate in 8 ply (from the root) at some node that is 3 ply deep then what you really have is mate in 5 ply (from here). That is the number you want to hash. Then when you pull it out of the hash you can readjust it... Say you pull it out of the hash at a node that is 6 ply deep in the search. You say "ah, this move is mate in 5 ply from here, and I am 6 ply deep, so it's real score is mate in 11 ply (from the root)". Or you can do what Bruce talks about which is when you store a mate-in-n exact score in the hash just convert it to a upper or lower bound of mate-in-100 and forget about it. I don't know what this mate distance pruning stuff is though. Good luck, Scott
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