Author: Peter McKenzie
Date: 15:37:59 05/23/02
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On May 23, 2002 at 12:53:40, Miguel A. Ballicora wrote: >On May 23, 2002 at 03:40:29, Steve Maughan wrote: > >>I have recently been tinkering with threat extensions (TE). I'd definitely like >>to include some form of TE but I have encountered some problems of tree >>explosion. >> >>What is happening is that the null move routine is detecting a mating threat and >>I'm extending by one ply at ply[x]. I then try a move (at ply[x]) that doesn't >>aviod the threat. In reply the opponent plays a sub-optimal move at ply[x+1] >>that does not lead to mate even though a forced mating move does exist. At >>plt[x+2] I then detect a threat and extend again... >> >>This sequence leads to a tree explosion. Is there any common wisdom as to how >>to avoid this? Some ideas that I've had are: >> >>1) Only extend by a fraction - inelegant solution IMO I wonder why this is inelegant? I would say the opposite. >>2) Store the rely to the null move that gave the checkmate and make this the >>Killer move for the next ply - didn't seem to work well - still some tree >>explosion. >> >>Has anyone any ideas? > >I do not have explosion when I do something similar to what you say, but I do >not know why. I think that I do what andrew suggests, I limit the number of >extensions in a line (I'll have to check). Also, I guess that the killers should >take care of most of the problems. > >Are you sure that the killer is included in the right slot? i.e. if white >killers are in "even" indexes (killer[2], killer[4] etc.) black killers should >be in odds indexes (killer[1], killer[3] etc.) even if you do a nullmove. >In other words, when you do "nullmove" make sure that you increase the "ply" >counter too. Othewise, you end up storing a white killer when it is black turn. Yes, this is a good point. Perhaps killers could be given an extra high ranking if we detect this situation? Eg. following a nullmove which indicated a mate threat. > >Regards, >Miguel > >> >>Thanks, >> >>Steve
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