Author: Vincent Diepeveen
Date: 17:37:23 05/05/04
Go up one level in this thread
On May 05, 2004 at 19:36:23, Robert Hyatt wrote: >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... You talk about 16 shit processors or so from a 1Ghz. I talk about a more modern 512 processor Cray made out of alpha 21264's :) You never grow up. Talking about machines from the past which do not even boot anymore :) Next cray is in fact an opteron cluster created out of each node = dual opteron. They wanted first to use the HT to connect to other nodes, but didn't succeed yet in that, so the in between model is using pci-x cards. When they get HT to work for the interconnects now *that* will kick some butt :) But even then diep would run *great*. The highend pci-x cards are 3.5 us latency from myrinet (one way pingpong), so a full latency to get a hashtable position is like 7 us only... Now try to run full SMP on that :) > >> >>This 1024 processor R14000 replaced in fact a huge old Cray that we see you post >>so much about...
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