Author: Robert Hyatt
Date: 08:55:07 05/05/04
Go up one level in this thread
On May 05, 2004 at 09:37:14, Marc Bourzutschky wrote: >On May 05, 2004 at 09:14:50, Mike Hood wrote: > >>On May 05, 2004 at 08:12:44, Vincent Diepeveen wrote: >> >>>On May 05, 2004 at 07:47:57, Mike Hood wrote: >>> >>>>I just let Filemon run while loading Fritz 8 to see why it takes so long. I was >>>>shocked to see that during the initialisation Fritz tries to open every possible >>>>tablebase. For instance... >>>> >>>>Open kpk.nbw.emd -- good, it's there >>>>Open kpknbw.emd -- file not found >>>>Open kpk_nbw.emd -- file not found >>>>Open kpk_nbw_emd -- file not found (I never knew this format was valid) >>>>Open kpk.nbw -- file not found >>>> >>>>And the same five accesses for the nbb file. >>>> >>>>Why carry on with the other three after finding the first tablebase? But it gets >>>>even wilder when it comes to the 6-piece tablebases. All 365 possible tablebase >>>>pairs in all possible formats are accessed, even though I don't have any on my >>>>disk. Thousands of "file not found" results. Just one example, to show how >>>>ludicrous it is: >>>> >>>>First Fritz tries to open krbnkp.nbw.emd, krbnkpnbw.emd, krbnkp_nbw.emd and >>>>krbnkp.nbw.emd. Almost the same as before, except Fritz is assuming 6-piece >>>>tablebases are compressed. But then Fritz tries to open krbnkp.0.nbw.emd, >>>>krbnkp.0_nbw.emd, krbnkp.0nbw.emd and krbnkp.0_nbw_emd. Then krbnkp.1.nbw.emd, >>>>etc... and krbnkp.2.nbw.emd... and all the way through to krbnkp.g.nbw.emd. That >>>>means 136 disk accesses for a tablebase that I don't have! And that's only one >>>>tablebase out of 365. >>>> >>>>Wouldn't it be much easier just to scan the tablebase directory and only open >>>>the files that actually exist? >>> >>>Both nalimov and i do this in a similar way. >>> >>>If you are willing to write code for this that works faster and works both for >>>windows and *nix, then i will be real happy to use it. >>> >>>Best Regards, >>>Vincent >> >>Thanks for the info, Vincent. I assumed the initialization code had been written >>by Chessbase, not by Eugene. >> >>My math was a bit off in my original post, but after looking at Filemon's log I >>can give the exact figure: Fritz attempts to access 33647 non-existent tablebase >>files. And please... you can't tell me that if the file krbnkp.0.nbw.emd doesn't >>exist it still makes sense to look for krbnkp.1.nbw.emd, krbnkp.2.nbw.emd, etc >>all the way to krbnkp.g.nbw.emd. That's a waste of processor time on any >>operating system. > >As this is only done once during initialization it is not such a big deal. IMHO >a more serious nuisance is that all available endgames on the paths are >initialized even though they may never be used. As a fair amount of memory is >taken up by each endgame that is initialized this is a serious inefficiency. >I'm surprised that Fritz and Co. have not implemented a scheme where an endgame >is only initialized when it is actually required. > >-Marc Would you _really_ want to wait until you have a few seconds left, with no increment, then start opening files, malloc()'ing buffers, setting up the decompression stuff? Oops. flag just fell. :)
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