Author: Steven J. Edwards
Date: 06:22:31 05/28/98
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Concering binary searches of linearly ordered opening book position libraries, I have found that the probe overhead is really nothing to worry about, at least when the library is on a reasonably fast hard drive. A million position library takes only twenty probes and with about 5 ms per probe it's only a tenth of a second total. Using a CD-ROM will be a little longer, but even then it's not going to be a whole lot of time. Furthermore, a decent OS will cache a lot of the probe blocks seen in the first few comparisons anyway. And if you really want speed, you can cache the top 1024 (ten levels) of comparison records yourself. It is true that a file sort of an oprning library is not the fastest thing to do. But it only has to be done once. Furthermore, it you for some reason want to experiment with a having lots of changes in the library, I would suggest having multiple library files and then fiddling with the contents of the smaller ones. With disk space being relatively inexpensive, and particularly if you want to have a massive library, I suggest tha you use a 64 bit hash code instead of 48 bits. It's cheap insurance. And yes, I have seen false matches with using only 48 bits. There is the question also on how big the library has to be. Having a million position library will cover just about all of modern GM praxis well into the middlegame. Scanning PGN files is the way to go. Years ago I had tried typing in chunks of ECO, but it's kind of a drag. The question is how deep to go in a game while recording the positions; I have this set to 48 ply in OCD which seems to be a reasonable number. Aslo, is it necessary to store lossage counts? I would think that there might be a better idea here to somehow take advantage of the PGN Date field to have a weighting factor to select mroe modern moves over older variations. Or maybe jsut exclude games older than N number of years from the original construction scan. -- Steven (sje@mv.mv.com)
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