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Subject: Re: Mathematical question regarding chess

Author: Adam Oellermann

Date: 09:22:52 08/01/01

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On August 01, 2001 at 12:20:42, José de Jesús García Ruvalcaba wrote:

>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.

Good points. I'm still having a little difficulty imagining what kind of chess
would be played by a USCF ELO 100 player.

- Adam



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