Author: Christophe Theron
Date: 15:18:17 12/23/03
Go up one level in this thread
On December 23, 2003 at 17:43:27, KarinsDad wrote:
>On December 23, 2003 at 16:53:44, Dann Corbit wrote:
>
>>On December 23, 2003 at 16:35:02, KarinsDad wrote:
>>
>>>Another point is that you only need 62 bits to indicate piece/pawn location (the
>>>position of the kings is already known).
>>
>>With these two changes, you need a maximum of 166-4 = 162 bits to store a chess
>>position. Is that about what you had achieved befire?
>
>I do not remember what I had come up with before. At the moment (just messing
>around with it today at work since it is the holidays), I am probably in the
>ballpark of about 162 bits or so, but that is not verified quite yet (most
>standard positions are currently maxing at about 156 bits or so).
>
>20 bytes is the goal I think.
>
>Hopefully, I'll have my encoding schemes from before somewhere at home. I don't
>think I ever made it to 160 (161 or 162 sounds about right). Something to look
>at over my holiday vacation.
>
>
>>At any rate, it limits the maximum possible number of legal board permutations
>>to no more than:
>>2^162 = 5846006549323611672814739330865132078623730171904 possible positions.
>>(about 5.846e48)
>>
>>This does not (of course) take into account things like the half-move clock and
>>position repeat status.
>
>What is half-move clock???
>
>I've never considered position repeat status to be critical to position
>information, but if you do consider it so, it is normally +2 bits (0 repeats, 1
>repeat, 2 repeats). However, I have a way to hide this in the current sized data
>encoding as well. Thanks for mentioning it. ;)
Welcome back KarinsDad.
I don't think that repetition status for the stored position would be of any
use. The only useful information for draw-by-repetition or 50-moves-rule
detection is the position history itself (in the worst case it could include all
the positions of the current game), so I think you can just forget about storing
that repetition info in the position itself.
Christophe
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