Author: Don Dailey
Date: 13:45:36 12/03/97
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On December 03, 1997 at 16:11:44, Ernst A. Heinz wrote: >On December 03, 1997 at 15:54:41, Don Dailey wrote: >> >>[...] The only possible problem with Cilkchess is the extra state >>I will have to carry around. We basically encapsulate the position and >>supporting data structures for searching, in a structure we can neatly >>pass up the search tree and across processors. This turned out to be >>much more efficient than I thought it would be and is quite workable >>even >>for a serial program. We never unmake() a move and do not have a >>"master" >>board. We do try to minimize the total amount of state, the rotated bit >>boards will add somewhat to this state but it may be worth it. > >Yes, copying is efficient on the Alpha -- in "DarkThought" we can switch >between a global board with make()/unmake() move and copying with make() >move only. With board data structures <= 256 bytes both settings perform >about equal on the Alpha but *not* on most x86 CPUs where a global board >with make()/unmake() is much faster. > >With our brand new board data structure that comprises only 128 bytes >copying may well be faster on the Alpha ... > >> One possibility now that we have the superior bitmap data structure is >> to measure mobility by counting squares not attacked by certain pieces, >> probably just pawns. > >This is exactly how "DarkThought" has always done it and we are quite >satisfied with it. > >=Ernst= Hi Ernst, Do you give attacked squares partial credit or none at all? I read your article on Dark Thought. It sounds like you have a great program. I mentioned early that I only just recently heard of rotated bit boards. I heard about this from the article. I'm interested in what evaluation heuristics people apply to the queen. Currently we do nothing but I don't believe this is good enough. We occasionally find completely useless squares for the queen and this gets us into trouble. But mobility seems to have some bad side effects too. Does anyone want to share some info here? Don
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