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Subject: Re: Mathematical question regarding chess

Author: José de Jesús García Ruvalcaba

Date: 09:20:42 08/01/01

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On August 01, 2001 at 04:27:02, Adam Oellermann wrote:

[big snip]
>
>When I got started with my chess program, I wanted to test my move generation
>and so I implemented exactly that;  a program which would play chess by randomly
>picking a move. It played a few games against my wife, who is in the category of
>"knows the moves but hardly ever plays"; it never survived a middle game. I
>would suspect that even a four-year-old who knows that "it's good to eat the
>pieces" would win well over 99% of games, although obviously I don't have much
>in the way of stats.
>
>Some quick calculations in order to make this seem scientific...
>- Branching factor is (say) 20 for the first 20 ply. I know, it may be more.
>- Nothing reduces branching factor, because there is no eval/search
>- Assume that to have a decent position in the middlegame against a novice, you
>need to pick one of the top 4 moves in a perfectly-ordered move list.
>- after 20 ply, the odds of having a decent position are 0.2^10 (you're only
>playing alternate moves), which means the odds are 0.0000001024; or you'll get
>one decent middlegame in about 10,000,000.
>
>After that it gets worse; there are fewer good moves and potentially much more
>branching in the middlegame. I therefore can state with some confidence that the
>random-mover will never beat the 4-year-old. Implication: 4-year old is at least
>750 elo points ahead of the random mover; which means the random-mover is
>probably negative Elo (if such a thing is possible).
>

The four-year-old is going to stalemate the random mover in quite a few games,
so I think the Elo difference is smaller.
In theory there could be negative ratings, but all the chess organisations I
know have an absolute lower limit for a rating, the lowest I have read is 100
(yes, one hundred) for the USCF.
José.


>Puts me in mind of a big heap of monkeys, a big heap of typewriters, and
>Shakespeare.
>
>Cheers
>Adam



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