Author: Melvin S. Schwartz
Date: 16:48:44 06/30/99
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On June 29, 1999 at 01:52:02, Mike Hood wrote: >On June 28, 1999 at 12:51:42, Melvin S. Schwartz wrote: > >> >>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 > >After reading your message I decided to run a little test the only way I know >how. I ran the Fritz engine against itself in an engine-engine match with >Selectivity parameters of 2 and 0 respectively. After 12 matches Fritz-Sel-2 had >won 8, lost 2 and drawn 2. That's admittedly only a small sample, but it >confirms my suspicion that the default setting makes the playing strength >stronger. Maybe we could get a more interesting result if we played both >versions of Fritz against a stong non-null-mover program. That's beyond my >testing capabilities though. > >Mike > >P.S. If you want to try this yourself, I had to resort to tricks to play Fritz >against itself with different parameters. I had to make a copy of the engine >file, Fritz5-32.eng, then edit the copy to fool the main program into thinking >it was a different engine. Hello Mike, Thank you for the interesting test results which I think are indicative that the default setting for Fritz is optimium. Regards, Mel
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