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Subject: Re: An idea for saving space in tablebases

Author: blass uri

Date: 06:56:20 10/09/98

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On October 09, 1998 at 09:35:55, Robert Hyatt wrote:

>On October 09, 1998 at 08:54:02, blass uri wrote:
>
>>
>>On October 09, 1998 at 08:10:51, blass uri wrote:
>>
>>>I think it is better to store the number of moves to win in the tablebases only
>>>if this number is divisible by 2 because otherwise you can compute the number of
>>>moves by search.
>>>
>>>Maybe it is possible practically to store it only if it is divisble by 3 or 4 (I
>>>do not know what is the speed of reading the tablebases from harddisk)
>>>
>>>Uri
>>I think it is easy to save at least 1 bit per position by this idea if in
>>positions when there is win in N when N is divisible by 2 you store win in N/2
>>and in positions when there is a win in N when N is not divisible by 2 you store
>>a win in 1(you can discover by search that it is not truth).
>>
>
>
>this is imposible to do.  KNN vs KP is a mate in over 100 moves.  How do
>I separate mate in 50 from mate in 100?  I certainly can't search to find
>this out...

I mean that when you store the number N/2 you mean win in N

you have only to search 2 plies because if you have mate in 99
the tablebases will tell you the number 1
You know by search that there is no mate in 2  but you have in the tablebase
mates in 98 so by  searching 2 plies you can read from the tablebases the mate
in 98 after 2 plies.
Searching 2 plies and reading the tablebases after every 2 possible plies(you do
not need every 2 possible because of the alpha beta  is not impossible
>
>
>
>>By this idea you can use the same number of bits to every position.
>>
>>If you want to use different number of bits to every popsition you must add 1
>>bit
>>to tell if the is a position with win in number of moves divisible by 2 or not.
>>
>>of course if you lose it is not important to know the number of moves.
>>
>>I use the word win and not mate because it is a mistake to use mate
>>because of the 50 move rule
>>
>>Uri
>
>
>distance to conversion has the same 50-move problem...

why?
If the distance is more than 50 then you know it is a draw.

Uri



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