Author: Chuck
Date: 04:01:41 12/12/04
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On December 11, 2004 at 09:51:34, William Penn wrote: >Shredder 8 tip: use Tablebase subsets > >There is far too much hard drive churning with Shredder 8 as simple endgames >approach. The slowdown is enormous. The kN/s speed may drop to 10% of normal. I >also fear for the life of my hard drive with such constant heavy churning. > >To return my system to sanity, I've developed some subsets of the tablebases >which can generally be used with reasonable demands on my computer system. Of >course the 3-4 piece TBs cause no problems, so can be used anytime. Only the >bigger 5 piece TBs are causing the problem. As a rule of thumb selecting TBs of >about 35MB or less is acceptable, and that comes to about 1GB total TBs. >Selecting TBs of about 70MB or less is sometimes acceptable, and that comes to >about 2.3GB total TBs. Of course the complete 3-4-5 piece TBs come to 7GB total, >but my computer just can't handle them in simpler endgame positions. So there's >no point to even considering the huge 6 piece TB files. > >FYI I'm running an XP 2400+ processor at 2GHz with 1GB RAM. > >It also helps to reduce the hash size. I normally run about 640-768GB hash, and >reducing that to 256MB or 128MB improves the TB access situation. But sometimes >that's just not enough in simpler endgame positions, so a smaller set of TBs >must be used. > >This problem is far less severe with other engines. Shredder 8 is the worst, and >the only engine I've tried that requires this kind of special compensation. I >hope they will fix this in Shredder 9. >WP I'm surprised at what you're saying here. So are you still using Shredder 8 for your analysis? I wonder if you have determined that it is the best engine for analysis despite the flaws you've noticed and by how did you determine it was best? It seems more likely to me that the analysis problem you mention is due to the large hash tables than the tablebases. Conversely, it seems that large hash tables should reduce the number of tablebase accesses, but that is not what you're reporting. If you point out a few positions, either by posting here or email them to me, I can test them on my computer and see if I encounter the same flaws. I do agree with you that Shredder 8 gets far more tablebase accesses than other engines, but I consider that a strength. It seems to me that when you are doing deep analysis, you want as many tablebase hits as possible, since they are 100% accurate. For me Shredder 8 has always scored well in long and short games, but I haven't been able to run the number of games at super-long time controls that would convince me which engine is the best. In the CB interface, perhaps you might try increasing the cache for tablebases to a large number and see if that improves the analysis. Regards, Chuck
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