Author: Ed Schröder
Date: 10:33:30 10/04/98
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>>Through the years I have experimented with this many times and in many >>forms. My conclusion is you gain lots of speed increase resulting in deeper >>search. Sofar so good but I also noticed the positional understanding drops >>considerable so in the end I dropped the idea. Similar experiences? >Oops -- Ed, >I forgot to ask if you are willing to disclose some technical details of >the techniques that you tested and experimented with. >=Ernst= It is certainly years ago I worked on the ideas you brought up here so I don't know all the details anymore however I will give it my best shot. First you have to understand Rebel is no "null-move" program (and probably) never will be so "selective search" is done in a total different way as these days is common using "null move". Rebel's selective search basically is the "static score" coming from the standard evaluation function which is compared to ALPHA first. Next a lot of exceptions (say chess knowledge) are checked. Based on all the information the selective search decides to a complete prune (the very bad ones) or to reduce the depth with 2 plies (the bad ones) or to reduce the depth with 1 ply (bad, but give it a try anyway) or leave the depth unchanged (good moves). In the selective part I have tried the ideas you mention on the last 2-3 plies and even on all plies of the selective search. It speed-up Rebel tremendously in the sense of a much higher iteration depth but I always had bad feelings about the algorithm (loss of positional understanding) which later was confirmed by the results I got from auto232. And - / - means drop the idea. The idea still has my attention, after all these are the days of Pc's on 450 Mhz and my last tries are from the ChessMachine 16 Mhz days if memory serves me well. - Ed -
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