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Subject: Re: Approximate # of Unique chess positions (FEN working)

Author: Sune Fischer

Date: 03:55:11 01/19/02

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On January 19, 2002 at 06:26:17, Uri Blass wrote:

>>Oh, so that's what you mean, well I'm not concerned with counting *too many*
>>squares since is was supposed to be an upper bound anyway. That it was easier
>>when the capturings began.
>
>I believe that a better upper bound can be achieved by giving every pawn 48
>squares.

That isn't possible with 32 pieces, and with 31 I assumed a promotion and 64
squares.
My plan was to get a descending sequence, but the promotion factor does blow
things up beyond my wildest dreams.

>The advantage is that the order of pawns is not important and when you assume
>only 24 squares for the d or the e pawns the order of pawns is important.
>
>I remember that the upper bound of my program(the last number that was posted)
>was better than the upper bound by your calculation.

What is your lowest upper bound?
I get 10^46 when running your code.

>>
>>I did think of one interesting example;
>>24 pieces with 12 pawn promotions (I think that is possible):
>>2*4^12*(64*(64 - 4)*62!)/((62 - 22)!*(2!*3!*3!*2*2)^2)
>>=5.99*10^43
>>
>>It is the highest number I can produce;)
>
>It is possible to get 12 promotions even with 28 pieces(one capture can lead to
>3 promotions)

You are correct Sir.
But the number can be cut down, if e.g. you choose 9 queens, there is a 9!^2
pulling the other way.
The largest weight is achieved with equal number of Q,R,N and B. The number of
ways that can be chosen is way lower than 4^16, but not sure by how much.

-S.



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