Author: Robert Hyatt
Date: 16:36:23 05/05/04
Go up one level in this thread
On May 05, 2004 at 19:22:40, Vincent Diepeveen wrote: >On May 05, 2004 at 16:44:59, Robert Hyatt wrote: > >>On May 05, 2004 at 16:28:35, Vincent Diepeveen wrote: >> >>>On May 05, 2004 at 11:56:21, Robert Hyatt wrote: >>> >>>>On May 05, 2004 at 09:29:19, Brian Kostick 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. >>>>> >>>>> >>>>>Could you report the time from the first tb until the last? I know it will >>>>>change from system to system but curious just to know how long it takes there. >>>>>BK >>>> >>>> >>>>About 10 seconds on my box with about 1/2 terabyte of egtbs in use, maybe a tad >>>>less than 1/2 terabyte.. >>> >>>About 3 hours for a 512 processor supercomputer though with 512GB ram and 1 TB >>>i/o. >> >>So? It would take about 1 second on a Cray T932. >> >>But how would you know since you didn't have any? More made-up numbers??? >> >>I can open all the 6-piece files over NFS in a couple of minutes on my laptop... > >Oh Cray would crash when initalizing at 512 processors the egtb's. It doesn't >have that many file handles in its OS as you must locally initialize >everything... You don't need that many file handles on the Cray I mentioned. It is fully SMP shared memory. N files == N file handles, even though not all are kept open all the time... What you mean by locally on a T90 I have absolutely no idea... > >This 1024 processor R14000 replaced in fact a huge old Cray that we see you post >so much about...
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