Author: martin fierz
Date: 02:56:46 06/21/01
Go up one level in this thread
On June 20, 2001 at 14:25:03, John Hatcher wrote: >Maybe the answer to my question is obvious, but I'd be interested in what >programmers have to say on the subject. > >I've recently been running matches between Fritz6 and Chess Tiger. On my old >Celeron 333mhz computer Fritz6 runs at about 250 knps, and Chess Tiger runs at >about 80-100 knps. To my delight, and surprise, Chess Tiger is doing very well >against Fritz - very well. > >Since, as I understand it, "nps" is related (at least nominally) to search depth >in a given time period, it would seem that, all things being equal, the greater >the "nps" the stronger the program. > >Of course, things are never really equal between two programs. As evidence of >that, Chess Tiger with its lower nps holds its own quite nicely against Fritz. >For this to happen it would seem that Chess Tiger must have some chess >"knowledge" programmed into it that allows it go toe-to-toe with a program that >searches 2.5x as many positions per second. > >Is the programming of this chess knowledge, even among the programmers of top >commercial programs, still as much art as science so that the programmer of >Chess Tiger has found a "smarter", more efficient way to implement chess >knowledge into Chess Tiger. I guess I supposed that much of this knowledge >would be common currency by now. > >Sorry for the long-winded question. I wanted to be clear. > >JOHN in my checkers program, i have various move ordering schemes. if i turn them on, i get much less nodes/seconds, but i can search deeper all the same. the same goes for ETC - using it lowers nodes/sec, but has a net positive effect. i can choose to run my program at 1.1MN/sec without these things or at 750kN/sec with them, and it's better in the 'slow' mode. there may also be a big difference in the eval. i know fritz does something fast but stupid: before starting the search, it assigns pieces values depending on which square they are. these values remain unchanged during the search (AFAIK). the result is a fast search but a dumb evaluation - i'm sure they tested it and found it to be ok, but it can be very irritating at times. it is of course well-known that if you have a king which is not too safe, you should try to exchange queens. fritz eval understands this, and gives the attacking side a bonus - BUT: in the lookahead, it keeps this in, even if the queens are traded. it will evaluate a line with a queen trade as +1 for the side with the safe king, but once the queen is gone, it will suddenly say 'equal' - which is correct, but it didnt see it in the lookahead. i find this very disconcerting when analyzing games with fritz... cheers martin
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