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Subject: Re: "unintended features" very funny ;-) NT

Author: Russell Reagan

Date: 14:14:35 08/19/03

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On August 19, 2003 at 17:04:44, Dieter Buerssner wrote:

>First I thought: don't clear the bits. With every new search, toggle the
>"current_age_bit". Add little logic to Probe/Store functions (it should not
>decrease efficiency much, because we need a slow memory look-up anyway), that
>just assumes the entry is empty, when the bit does not fit.
>
>But at second thought, this would not really help. Because the new search might
>not touch one entry, and the second new search would assume, that the entry is
>current. So, there is again an influence of the history of the game due to TTs,
>something that Johan wanted to avoid from the start.
>
>Another approach would be, to have the age bits in one seperate small table.
>Assuming you have 64 Mb hash, with 16 bytes each entry, this would be 4 million
>bits, or 1/2 Mb of RAM. Something that probably would stay in second level cache
>most of the time on a modern computer. Clearing would use practically no time,
>but accessing the second table would mean some overhead.

You could make your initial idea work, by using a byte instead of a bit. Johan
said in another post that his hash entry was 30 bytes in size. Adding an extra
byte wouldn't increase memory too much (31 MB instead of 30 MB for instance),
and you would have to play 128 moves (256 ply) for the same "current age byte"
to appear again, and by that time there will surely be no old positions left
from 256 ply into the past.



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