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Subject: Re: How much endgame tablebase cache? (nt)

Author: Richard Pijl

Date: 07:15:07 06/30/05

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On June 30, 2005 at 01:26:13, Ray Banks wrote:

>I use 32MB, but to be honest I haven't seen any difference no matter what I set
>it at (up to about 128MB is the highest I've gone I think). Still get a lot of
>disk activity. One of my machines has plenty of RAM so I'm going to try 256MB as
>has been suggested here to see what effect that may have

Make sure you understand what the cache does, and in what other places disk
accesses are cached.
The TB cache is storing uncompressed, unpacked EGTB entries. I think it picks up
a block of entries at the same time but I'm not sure about that.
Another type of cache is the disk cache of the OS. This cache stores chunks of
the file you've read, so compressed EGTB blocks. It is easy to see the effect of
the windows cache by setting up a testposition that would get quite a few EGTB
hits (some 8-piece position or so) and run it after a clean start of your
machine. After a minute or so, reload the engine and do the same testposition
again. You'll see it will run without many disk accesses for a few seconds,
getting quite deep fast (compared to the first test run) and then starts
accessing the disk again.
So if you want to save on disk accesses, it is probably wise to have a small TB
cache. If you want to optimize for speed, a slightly bigger TB cache is probably
better.
Note that the effect is probably bigger when running engine matches on the same
machine. The TB cache is not shared between the engines, whereas the Windows
cache is.
Richard.



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