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## [Bug-gnubg] Re: Snowie error rates versus gnubg error rates

**From**: |
Christopher D. Yep |

**Subject**: |
[Bug-gnubg] Re: Snowie error rates versus gnubg error rates |

**Date**: |
Tue, 03 Jun 2003 23:20:19 -0400 |

`First, as a quick aside, let me note that this is my first post to the
``group. On May 27, I downloaded GNU Backgammon (for Windows) for the first
``time (May 24 build). I have been extremely impressed with all the features
``packed into GNU. Also, as far as I can tell, the playing strength of GNU
``is comparable to Snowie 3. From my small selection of positions tested, it
``is in fact stronger than Snowie 3.
`

`Thank you to all who have worked on this software for so many years. It is
``truly amazing that such a fine piece of software is free to download!
`

`I subscribe to the daily digests, so I hope this response turns out fine
``(if not, let me know). Hopefully you'll find this information useful.
`

`I've used Snowie 3 for 3.5 years (since it's release). I analyze all my
``online matches (500+ matches) as well as some of my live matches. A number
``of years ago I did my own study of Snowie error rates. I came up with the
``following Snowie error rate definitions:
`
Error rates for player 0:
Chequerplay error rate: Em(0)/(m(0)+m(1))
Cube error rate: Ec(0)/(m(0)+m(1))
Total error rate: (Ec(0)+Em(0))/(m(0)+m(1))

`I.e. the error rate for both chequerplay and cube has nothing to do with
``the number of cube decisions. On the other hand it uses the total number
``of chequer plays for *both* players as the denominator.
`
Here m(0) = number of chequer play decisions for player 0,
m(1) = number of chequer play decisions for player 1
Em(0) = total normalised error for chequerplay decisions for player 0
Ec(0) = total normalised error for cube decisions for player 0

`I tested the above definitions and they always matched exactly, up to
``round-off error, in Snowie 3 (I don't have Snowie 4 and never had Snowie 2).
`

`Note that m(0) is approximately equal to m(1). Also note that when player
``0 has cube access, m(1) is approximately equal to c(0) (i.e. my formulas
``essentially agree with your formulas when player 0 has cube access 100% of
``the time).
`
Can you check your formulas again?
Chris
PS: Thanks again for the great work you've done on GNU Backgammon!
At Sun, 06 Apr 2003 12:10:03 +0000, Joern Thyssen <address@hidden> wrote:

Hi,
I've studied snowie error rates versus gnubg error rates a bit:
m=number of chequer play decisions (m'=number of unforced moves)
c=number of cube decisions (c'=number of non-trivial cube decisions)
Em=total normalised error for chequerplay decisions
Ec=total normalised error for cube decisions
Snowie error rates:
Chequerplay error rate: Em/(m+c)
Cube error rate: Ec/(m+c)
Total error rate: (Ec+Em)/(m+c)
gnubg error rates:
Chequerplay error rate: Em/m'
Cube error rate: Ec/c'
Total error rate (Ec+Em)/(m'+c')

**[Bug-gnubg] Re: Snowie error rates versus gnubg error rates**,
*Christopher D. Yep* **<=**