Author: David Mitchell
Date: 13:43:19 03/09/04
Go up one level in this thread
On March 09, 2004 at 11:30:44, William Penn wrote: >On March 09, 2004 at 05:28:30, Albert Bertilsson wrote: > >>I'd just like to make one thing clear, the "churning" of the harddrive(s) is >>there because of the usage of tablebases. There is nothing that can solve this, >>having larger cache for tablebases help very little because the tablebases are >>so huge and you computer search very fast. Using faster drives (like scsi) will >>increase performance because of faster tablebase access times, but the drives >>will be working constantly at peek anyway. Turn of tablebases or get used to >>drive "churning", that is you options. > >There is another option! Reduce hash table size. Then the engine speed returns >to near normal. True, it doesn't seem to affect the churning, but the engine >then runs at near normal speed - which is an important improvement. > >>Using tablesbases give you perfect solutions to some positions but the obvious >>trade of is nps, I guess that many systems don't benefit very much from >>tablebases due to the reduced search speed. > >Again, reducing hash table size tends to keep nps near normal speed, in my >experience with a souped-up Compaq Presario/XP 2400+/1G RAM running Windows XP >Home. I imagine that most systems can use tablebases OK if that is done. The >problem is that most people want to use as big a hash size as possible, but that >incorrect when the endgame approaches and tablebase access starts to be >significant - reducing the engine speed greatly. > >>If you get a lot of harddrive noise you could try mounting your drive in some >>rubber bands instead of directly in the chassi to reduce the noise a little. > >I'm not concerned about the noise. My Maxtor drives have a "quiet" mode >available if I want to use it. But it slows down access somewhat, and the noise >is also a good indicator of what the drive is doing, so I don't mind the little >extra noise. > >>/Albert > >Overall, you should be aware that such extreme hard drive churning will reduce >the lifetime of the drive significantly. Hard drives have a finite lifetime, and >can only seek so many times before the heads wear out eventually. Those who >write the code for chess tablebase access should keep this in mind, and do >whatever is necessary to improve it, and reduce the hard drive churning as much >as possible. There is really not much point to adding 6-man tablebases to most >ordinary computer systems until this churning problem is solved. >WP Good point about adjusting your hash table size for best engine performance in Windows. Hard drive heads however, ride on a stream of air produced by the rapidly spinning disk platter. Minus dirt and dust collisions with suspended particles in the air, not much "wearing" going on. The levers that move the head are another matter. Back in the somewhat early DOS days, some IDE controller cards (the IDE functions were not on the mobo at that time), actually had memory slots you could fill as a HD cache. Paradise was one brand I recall. If you had to access the HD a lot, having several extra MB as a hard drive cache was a big speed up. Very nice! Possibly something like that could be done today, replacing the drive card/OS HD cache memory with something _really_ big. That would not stop all the disk activity, but it would certainly help speed up TB access, and save a lot of disk activity, too. Probably wouldn't be worth it for the occassional user, but for a tournament computer, it'd be worth it. dave
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