Author: Dann Corbit
Date: 18:10:20 11/18/99
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On November 18, 1999 at 20:43:20, Fernando Villegas wrote: >Hi dan: >This issue of plys, querality of the game, etc, is tricky. Seems to me -but I am >not programmer, so this is more a question than an aseveration- that deeper >search it cannot never be disociated of greater knowledge or whatever the name >you give to the criteria with which the program prunnes. More plys means more >moves to analyze and so more prunning to get a choice, but then more prunning >means -¿?- more parameters to do it decently. I suppose the package of ideas >with which you get a fair selection in the area of, say, 4 to 7 plys, cannot be >the same for the area of 8 to 12 and so on. You need -¿?- more refined criteria. Actually, I pretty much agree with everything you say here. There are two kinds of plies. One is an exhaustive search of a ply. Very few programs really do this since most of them use NULL move pruning, which means that *all* plies are really selective. Then there are extensions. For instance, if there are repeated captures or checks or something interesting that makes the program peek forward, it may be possible to see very deeply in a very short time. This kind of ply is very selective. Selective plies means that we incorporate knowlege. The smart searchers are (undoubtably) incorporating great amounts of knowlege in order to figure out where to exert the energy of searching. >Other thing is the quality of them. They can be sophisticated but ineficient. >You can go deep even with the utmost silly ideas, by example, just looking for >exchanging pieces as in some games played by kids or patzers. So maybe for a >certain deep you need more knowledge, BUT then it appeasr the problem that there >is a number of posible different packages of ideas of very different quality. Indeed, what you are talking about is the type of extension employed to tell the program how to guess where to search. If two successive moves tell me that first I lose my queen and then a rook, it seems likely that I will stop exploring that pathway. Once in a great while, it may cause me to miss a checkmate but most of the time it will mean that I spend my energy searching where it is wiser to hunt. The type of speculation used to extend plies will cause the quality of the extensions to be preferred or to suffer. If >all this is true, then: >a) An increment of plys with the same knowledge package produces a diminishing >return or even beyond some threshold can produce an awful result. I think the next ply always gives you the same bonus, but each bonus becomes more and more costly to achieve so I believe that I agree with you. >b) An increment of knowledge not neccesarily produces better selection. For each additional ply searched, there is a 17% chance to change your mind about the move chosen [IIRC] according to the "Goes Deep" studies by Hyatt and Heinz [again IIRC]. Anyway, if you just chose a move, it may turn out that the next ply will reveal it is a disaster. So (if I understand your conjecture) I believe I agree with you again. >By the way, I have the impression that Tiger has been developed on the ground of > the following idea: the progam is divided in different nodules of knowledge >that are activated according what is happennign in the game. Perhaps this is >not not really a new idea, but a considerable greater development of it could be >so... You probably know better than me, because I suspect your knowledge of chess is better than mine. >Hope not to disturb you with these musings of a non programmer amateur I think we agreed on everything. A little scary, isn't it? Probably just means that we're both wrong. ;-)
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