Author: Peter McKenzie
Date: 15:53:38 02/01/01
Go up one level in this thread
On February 01, 2001 at 13:35:23, Dann Corbit wrote: >On February 01, 2001 at 02:43:44, David Blackman wrote: > >>On January 31, 2001 at 19:14:19, Dann Corbit wrote: >> >>>On January 31, 2001 at 11:36:01, Robert Hyatt wrote: >>>[snip] >>>>The idea seems pretty good for 3-4 piece files, and even for 5 piece files >>>>although the memory to hold them becomes prodigous. But 6's are hopeless >>>>as todays machines are no better at probing a 1gb file than they are at >>>>probing a 1 terrabyte file. >>> >>>It might be worthwhile to store them in a real database with hashed index. >>> >>>Modern database systems will cache database requests very efficiently, and so I >>>think it might be doable. The database model would be the hard part (finding a >>>representation which is still highly compact like the tablebase files) >> >>Modern database systems are pretty hopeless for raw speed and space efficiency. >>A custom built data structure is almost always faster and smaller, and usually >>much simpler as well. >> >>The good things about modern database systems, are safe multiuser access and >>update, robustness in the face of various disasters including hardware failure, >>reliable backups that can be done even while transactions are in progress, nice >>system administration tools, nice programming tools for building simple GUI >>programs for end users, a highly generalised and flexible query mechanism, and >>so on. >> >>All of these good things are irrelevant for endgame tablebases, and the >>performance cost would really hurt. > >We have machines here which have more than 500 MB/sec IO bandwidth. They can >read tablebase files in the time a PC can open one. I am speaking of a real >database system, not a toy. You are thinking of a PC. I am thinking of an IBM >3090, RS/6000 or multiple CPU Alpha machine (we have all of these in house). I think the point was that using a good optimised custom database format/library (such as tablebases) will tend to be faster and/or more space efficient (depending on design goals) than using a generic database management system. I don't think the type of machine you use changes the basic soundness of this point. Of course custom database formats have disadvantages (extra development time, lack of compatiblity with standard query tools etc) but they can definitely go faster and/or use less space.
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