Author: Uri Blass
Date: 03:29:37 08/30/02
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On August 30, 2002 at 05:51:37, Sune Fischer wrote: >On August 30, 2002 at 05:26:04, Uri Blass wrote: > >>This is exactly the case for Junior and Fritz and they simply do not care about >>small improvement that they can get. >> >>They know that there are positions when the program cannot see simple tactics >>but they do not care to fix it. >> >>There are positions when Junior cannot see simple tactics and Amir ban knows >>about it but he did not fix it at least not in Junior7(some years after he got >>the information). >> >>There are positions when Fritz cannot see simple mate because of null move >>pruning. > >I think they do care, but if it's only in a few weird special cases then it's >not important. They tune their programs for the most likely positions, not the >most unlikely ones. It will cost too much in normal positions if they have to >take care of all the special cases. > >>I also know that not seeing simple tactic may be relevant in rare cases >>for games but they do not fix it by having some verification search against >>zunzwangs and it is possible to have verficiation search(yace does it). > >I don't know what a 'verification search' is, but I bet it isn't free to do, so >in some positions they surely must be weaker because they 'waste' time on this >verification. It is better to be 0.1% slower in order to avoid stupid mistakes even if the mistakes happens only one time out of 500 games and there was one engine-engine game when I saw a stupid mistake. I believe that they can do it. Here is a simple idea(this idea can be improved but the point is that even this idea can do their program better) Before searching if there is a threat to depth x>12 do a small search to depth ((x-10)/2) and get an exact score of the position when it is white to move and when it is black to move. If you see that the exact scores suggest a big zugzwang do not use null move pruning. The only reason that I did not use that kind of idea(with smaller number than 10) in movei is that I found that it cause movei to search more nodes in other branches of the tree so I guess that I should be careful to define a special search function that does not change history tables,killer moves or hash tables in order to use that idea in a productive way. Uri
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