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Subject: Re: Distinct position enumeration

Author: Ricardo Gibert

Date: 01:23:24 01/03/01

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On January 03, 2001 at 03:38:40, Andreas Stabel wrote:

>On January 02, 2001 at 17:05:13, Heiner Marxen wrote:
>
>>On January 02, 2001 at 04:45:47, Andreas Stabel wrote:
>>
>>>On December 29, 2000 at 10:26:06, Steven J. Edwards wrote:
>>>
>>>>Briefly, I have calculated the number of distinct positions after N ply for N
>>>>equals zero upto nine.  Can someone extend this series, or has anyone already
>>>>done so?
>>>>
>>>>1,20,400,5362,72078,822518,9417683
>>>>
>>>>See:
>>>>
>>>>http://www.research.att.com/cgi-bin/access.cgi/as/njas/sequences/eisA.cgi?Anum=057745
>>>>
>>>>-- Steven
>>>>
>>>>chessnotation@earthlink.net
>>>
>>>I have earlier posted the following table which, unfortunately, does not
>>>match your numbers after ply 3.
>>>
>>>Table from opening position:
>>>   |               | Unique nodes  | Unique nodes II Unique nodes  | Factor |
>>>Ply| Total # nodes | ep = pawn two | ep = oppositeII ep = Only if  | prev.  |
>>>   |               |               | pawn can hit II ep is legal   | row    |
>>>---+---------------+---------------+--------------II---------------+--------|
>>> 0 |             1 |             1 |            1 II             1 |        |
>>> 1 |            21 |            21 |           21 II            21 |  21.00 |
>>> 2 |           421 |           421 |          421 II           421 |  20.05 |
>>> 3 |          9323 |          8023 |         5783 II          5783 |  13.74 |
>>> 4 |        206604 |        109262 |        77796 II         77796 |  13.45 |
>>> 5 |       5072213 |       1351950 |       898812 II        898812 |  11.55 |
>>> 6 |     124132537 |      15334851 |     10281864 II      10281862 |  11.44 |
>>> 7 |    3320034397 |     160373323 |    106193912 II     106193643 |  10.33 |
>>> 8 |   88319013353 |               |              II               |        |
>>> 9 | 2527849247520 |               |              II               |        |
>>>
>>>
>>>Best regards
>>>Andreas Stabel
>>
>>Andreas, obviously you are summung up the numbers of Steven, i.e.
>>  21 = 1+20
>> 421 = 1+20+400
>>5783 = 1+20+400+5362
>>I did not check further.  (column opposite pawn can hit)
>>
>>Heiner
>
>Unfortunately you are wrong :)
>As you see from my comment above, I said that after ply 3 our numbers don't
>match. F.ex. your ply 4 gives 1+20+400+5362+72078 = 77861, and my number
>is 77796. It would be interresting to find out what is the correct numbers.
>
>Regards
>Andreas Stabel

The divergence at 4 ply suggests a difference on how each program deals with
checking moves.



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