Author: Gerd Isenberg
Date: 14:42:31 08/26/04
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On August 26, 2004 at 16:25:07, Lance Perkins wrote: >After seeing the posted NextMove code, I wonder how much better this is than >simply generating all the moves and then sorting them in one go. It depends on the design of the engine. In general it is a good idea to delay as much as possible and hope for an early cut. Beside hash or pv move, you often cut with winning captures, only generating them seems to make sense. Probably same for generating/trying killers. With classical board presentations, traversing the board in one direction with a sliding piece, it might be better, to generate quite moves on the fly into a separte move list, while looking for capture targets. Of course there is some waste of memory write cycles if generating all and early cutoff. Anyway, after hash/goodCaptures/Killers/EvalHints it might be the best to generate all remaining moves (captures, checks, winning double attacks) and to assign history/psq or whatever scores to them to pick the next best. With my current finite state movegen i delay/skip generating piece captures/moves to squares attacked by opposite pawns or other negative SEE values. With bitboards one may even keep legal move target bitboards, piece or direction wise. So you have an idea of the number of moves or stalemate without serialising moves into a list. > >This code is a little to complex and tool long for my liking, but if it offers a >very significant gain, maybe I should give it a second look. > >I can immagine that when one gets a cutoff, the rest of the moves don't have to >be generated (captures vs non-captures). However, in leaf nodes, one is very >likely to generated all the moves anyway. Leaf nodes, if not hash hits or repetitions, are eval cut nodes or stand pat nodes with no or only (bad) pruned captures because of eval+gain < alfa. The first one needs no generated moves at all the second only captures. Pruning might already considered during movegen. Simply use some counters and do some statistics. Gerd > >Has anyone compared these?
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