Author: Uri Blass
Date: 10:07:53 10/21/00
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On October 21, 2000 at 12:59:27, James T. Walker wrote: >On October 21, 2000 at 10:56:53, Uri Blass wrote: > >>On October 21, 2000 at 09:27:22, James T. Walker wrote: >> >>>On October 21, 2000 at 05:28:14, Uri Blass wrote: >>> >>>>I composed this position to see if chessmaster can see perpetual check. >>>> >>>>[D]4k3/6RQ/6PP/8/r7/8/r7/7K b - - 0 1 >>>> >>>>The target is to see 0.00 score >>>> >>>>I found that chessmaster does not see the draw even after some minutes but after >>>>Ra1+ Kg2 it can see the draw very quickly in clearly smaller depth. >>>> >>>>The same after Ra1+ Kh2 >>>> >>>>I tried also Fritz5.32 and it does not see the draw at least after a short time. >>>> >>>>If I give Fritz5.32 the moves Ra1+ Kg2 it can see the draw but after Ra1+ Kh2 >>>>it has problems to see the draw. >>>> >>>>Fritz5.32 expects Kg2 when it plays Ra1+ and wants to play Kg2 at depth 13 with >>>>evaluation 0.00. >>>> >>>>How many squares can the white king visit before the repetition?(it is clear >>>>that the white king cannot visit all the 21 squares (b1-b3... h1-h3)) >>>> >>>>Uri >>> >>>Hello Uri, >>>Why can't the White King visit all 21 squares? If the King takes the pattern of >>>h2,g1,g2,f1,f2,e1,e2,d1,d2,c1,c2,b1,b2,b3,b2,c3,c2,d3,d2,e3,e2,f3,f2,g3,g2,h3,h2,h1,g2,f1,f2,e1,e2,d1,d2,c1,c2,b1, >>>it has visited all 21 squares and taken 38 moves without hitting the same square >>>3 times. What did I miss? >>>Jim >> >>You missed the fact that computers are supposed to evaluated second repetition >>in the search as a draw. >> >>Uri > >Hello Uri, >I didn't know that. What is the reasoning behind that? There is a lot I don't >know about computer chess! :-) >Jim The reason is to save time. There is no reason to continue to search lines with repetitions because if you ignore them and evaluate them as a draw you have more time for other lines. If you can win material with repetition you can win the same material without repetition. The only exception is a repetition of previous positions of the game but here the repetition happens in the search. Uri
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