Re: [Bug-gnubg] Verification of hypergammon database

[Christian Anthon]

Okay, I think I've tracked the problem to a change made in November
2004, but somebody should check this once the change reaches the build
versions. I don't have the knowledge of what is right and wrong, nor
easy access to older versions of gnubg.

Christian.

On Sat, Dec 20, 2008 at 12:50 AM, Christopher Yep <address@hidden> wrote:
> Hi,
>
> I recently started playing around with hypergammon.  After getting some
> strange results, I found this e-mail sent to the mailing list on 1/18/2007
> (below).
>
> I was able to exactly duplicate Nikolay's results for recent versions of
> gnubg (from 2006 and 2008), but I got correct results for a version of gnubg
> from 2004.  This suggests that something may have changed with the
> hypergammon-3 evaluator (or at least how gnubg interprets the results of the
> hypergammon-3 evaluator) between 2004 and 2006.
>
> Here is the position referenced by Nikolay (Jacoby rule active):
>
>    GNU Backgammon  Position ID: ADAAAQAkIAAAAA
>                    Match ID   : cAkAAAAAAAAA
>    +24-23-22-21-20-19------18-17-16-15-14-13-+  O: gnubg
>    | X                |   |    X     X       |  0 points
>    |                  |   |                  |
>    |                  |   |                  |
>    |                  |   |                  |
>    |                  |   |                  |
>    |                  |BAR|                  |v (Cube: 1)
>    |                  |   |                  |
>    |                  |   |                  |
>    |                  |   |                  |
>    |                  |   |                O |  On roll
>    |    O             |   |                O |  0 points
>    +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: user
>
> I also did a quick test of a hypergammon-2 position (using a 2008 version of
> gnubg), which also gave incorrect results.  (I didn't check any
> hypergammon-2 positions with my version of gnubg from 2004).  So, the
> problem probably also extends to hypergammon-2 and hypergammon-1.
>
> I was able to duplicate Nikolay's result for two recent versions of gnubg:
>
> Windows XP, GUI multiple-thread version, version 0.90-mingw (build Apr 25
> 2008)
> Windows XP, GUI single-thread version, version 0.16-mingw (build Nov 20
> 2006)
>
> However, I do get correct results for a version of gnubg from 2004:
>
> Windows XP, GUI (single-thread) version, version 0.14-devel (build Apr 20
> 2004)
>
> The correct win/gammon/bg numbers are:
>
> 45.6%, 24.4%, 1.4%; 54.4%, 31.8%, 1.9% instead of 81.8%, 49.4%, 8.7%; 18.2%,
> 0.0%, 0.0%.  Obviously the second set of numbers is unreasonable (with O
> supposedly winning only 18.2% of the time with zero gammons).
>
> The correct cubeful equities are ND = -.219, D/T = -.710 (i.e. 2 * -0.3548),
> so the correct cube action is no double, beaver.  My 2004 version of gnubg
> gets everything correct.  My 2006 and 2008 versions of gnubg have problems.
>  If one tries to play the above position with tutor mode on (with my 2006 or
> 2008 versions), gnubg will complain if X fails to double (since gnubg claims
> that ND = .798 and D/T = 2.381, i.e. gnubg claims that it's a blunder not to
> double and that it's a huge pass).
>
> Chris
>
> At 05:02 AM 1/18/2007, Nikolay Marinov wrote:
>>
>> Hi All,
>>
>>   I have problem with hyper gammon database for 3 chequer backgammon. I
>> generate it myself and also download a generated copy from the internet, but
>> when I try to verify this databases with position
>>
>>        GNU Backgammon  Position ID: ADAAAQAkIAAAAA
>>                        Match ID   : cAkAAAAAAAAA
>> given in gnubg site I've got the following result:
>>
>> Position ID:    ADAAAQAkIAAAAA
>> Match ID:       cAkAAAAAAAAA
>>
>> Evaluator:      HYPERGAMMON-3
>>
>>            Player       Opponent
>> Position         3018          2831
>>
>> Owned cube                    : -0,0230
>> Centered cube                 : -0,2310
>> Centered cube (Jacoby rule)   : -0,2186
>> Opponent owns cube            : -0,3548
>>
>>       Win     W(g)    W(bg)   L(g)    L(bg)   Equity    Cubeful
>> static: 0,818   0,494   0,087   0,000   0,000    +1,218    +0,798
>>
>>
>>
>> Cube analysis
>> 0-ply cubeless equity  +1,218
>>  0,818 0,494 0,087 - 0,182 0,000 0,000
>> Cubeful equities:
>> 1. Double, pass         +1,000
>> 2. Double, take         +2,381  ( +1,381)
>> 3. No double            +0,798  ( -0,202)
>> Proper cube action: Double, pass
>>
>> which is slightly different from evaluation of the same position given in
>> the site. I try this in 0.14 and 0.15 version of gnubg on Windows XP SP2,
>> but both returns the same result.
>>
>> Do You have any idea from where this problem may come? Thaks in advance.
>>
>> Nikolay.
>
>
>
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