Author: Miguel A. Ballicora
Date: 09:53:40 05/23/02
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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 >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. Regards, Miguel > >Thanks, > >Steve
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