Author: Melvin S. Schwartz
Date: 09:51:42 06/28/99
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On June 28, 1999 at 01:24:49, Mike Hood wrote: >On June 27, 1999 at 22:06:48, Melvin S. Schwartz wrote: > >> >>On June 27, 1999 at 15:24:33, Gustavo Pereira wrote: >> >>>I have seen many posts where they say Fritz cannot solve this or that problem. >>>Many of the times it is because Fritz is (by default) a null mover. >>> >>>Now what is the reaction? >>> >>>Many people start saying that it is because Fritz is not a good program, and >>>that you can't switch off the null move engine. >>> >>>How far from reality!!! >>> >>>Quoting from the (really meager) Fritz 5.32 manual >>> >>>'(Selectivity) Denotes the number of plies reduced by the null-move. A value of >>>zero means that the null-move is switched off'. >>> >>>I guess that says it all. >> >>What effect would changing the default setting to zero have on Fritz's playing >>strength? >> >>Mel > >This is a theoretical question, probably better left to a chess programmer, but >I'll be the first fool to rush in. > >Many months ago I compared Fritz's performance with different Selectivity >settings. The higher the value of Selectivity (6 is maximum), the deeper >Fritz searches, ie the more plies it examines in the same time. At Selectivity 0 >Fritz doesn't search as deep, presumably because it examines lines it would have >ignored otherwise. However, the word "Selectivity" seems to be misleading, >because even at Selectivity 0 Fritz seems to be doing some "selection" of lines, >it seems to be too fast to be doing a Brute Force search. > >To put it succintly: the lower the Selectivity value, the less deeply Fritz >searches, but the more thoroughly it analyzes. This means that by setting the >Selectivity to 0, Fritz might avoid blunders like in the cute little chess >problem Kurt quoted, but Fritz could make other errors by not searching deep >enough. > >My guess (here is where I need backup from chess programmers) is that blunders >through null move errors are relatively rare. The advantages of deeper searches >far outweigh these occasional problems. > >Speaking practically... Fritz has seven different Selectivity values, from 0 to >6, and Chessbase has made 2 the default. I assume that this value has been >proven to produce the optimum playing strength, either experimentally or >algorithmically. I'm not sure if a higher Selectivity value brings advantages. >Maybe someone can present a position in which "Fritz Sel 6" finds the best move >in 10 seconds, whereas "Fritz Sel 2" needs 5 minutes. I'd be glad to hear about >it. Hello Mike, Actually I knew all that believe it or not. The reason I put up the question was to hear if someone actually had found Selectivity at zero producing a higher playing strenght, which would have started a whole new debate. The other reason I brought this up is because it has been said by Shep that his modified settings for CM5000K result in superior play. Therefore, it is not unreasonable that a possibility exists where the default setting is not optimum. Regards, Mel> >Mike
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