Re: [Bug-gnubg] Bearoff database question

[Joern Thyssen]

On Thu, Jun 10, 2004 at 07:04:41AM +0200, Joachim Matussek wrote
> Hello,
> 
> I just wanted to use bearoffdump.exe. Can anyone tell me how the
> positions are numerated within the bearoff databases. When i want to
> look for a special position?s output, how can i calculate its position
> number?

One-sided enumeration:

Assume you have C chequers and P points. The total number of one-sided
positions is binom(C+P,P).

000...0000 : #0

100...0000 : #1
010...0000 : #2
001 ..0000 : #2
000...0001 : #P

200...0000 : #P+1
110...0000 : #P+2
101...0000 : #P+3
...
020...0000 : #P+#P
etc.

That is, we start enumerating all positions with 0 chequers, then all
positions with 1 chequer, and then all positions with 2 chequers etc.

Two-sided enumeration:

two sided enum = 
   (one sided enum for player on roll) * binom(C+P,P)
   + (one sided enum for opponent)

I hope this helps!

This is the same enumeration used by Hugh Sconyers to index his
databases, except that he doesn't include position #0.

J?rn