Author: Vincent Diepeveen
Date: 13:26:19 05/05/04
Go up one level in this thread
On May 05, 2004 at 13:25:18, Marc Bourzutschky wrote: >On May 05, 2004 at 11:55:07, Robert Hyatt wrote: > >>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. >> >>:) > >I actually do just that and it takes a small fraction of a second to initialize >one tablebase. For me at least the likelyhood of this being an issue is >miniscule compared to the amount of memory I can save. However you will access about 30 huge 6 men egtb's which will take quite some longer to index. suppose your machine just starts swapping then thanks to doing major i/o for initialisation. FLAG.
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