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## RE: [Bug-gnubg] Bearoff dB position, few questions

 From: Alain Redlinger Subject: RE: [Bug-gnubg] Bearoff dB position, few questions Date: Fri, 26 Jun 2009 12:27:45 +0200

```I spent a lot of time trying to understand what is meant by equity in the
different dialog boxes and window panes. I read the
Equities explained chapter in the technical notes section of the GnuBG
(web) manual. As far as I could understand, there is
every reason for cubeless equities in money game and match play to be
different. In match play, the equity figure is in fact the
NEMG, i.e. the normalised equity money game. My understanding is that in the
computation of the NEMG the match score must be taken
into account, through a reference to the loaded match equity table, that is
probabilities of winning the match at the start of any
game at the different possible scores. No such thing in money game, where
cubeless equity is directly computed from the different
probability of the game outcome (win simple, win gammon, backgammon, loose
simple, etc.).  Could someone confirm this?

Alain Redlinger

-----Message d'origine-----
[mailto:address@hidden De la part de Misja Alma
Envoyé : vendredi 26 juin 2009 12:00
À : Christian Anthon
Objet : Re: [Bug-gnubg] Bearoff dB position, few questions

I tried to move the 2-sided db out of the way, like you said.
Just to confirm that I did it correctly:
I went to the gnubg folder on my (unbuntu) pc and did 'mv gnubg_ts0.bd
gnubg_ts0.bd_bak'
Then I restarted gnubg and entered the position, but the cubeless
winning chances are still different for money game than for a 3 pt
match.

Misja

On Fri, Jun 26, 2009 at 8:57 AM, Christian
> I believe that the cubeless data are extracted from the 2-sided db as
> well. This results may well be different from that of an evaluation
> using the one-sided db. Try moving the 2-sided db out of the way and
> repeat the experiment.
>
> Christian.
>
> On Fri, Jun 26, 2009 at 8:52 AM, Misja Alma<address@hidden> wrote:
>> Hi All,
>>
>> Thanks MaX for posting the question on this forum.
>>
>> So to Christian: You were saying that the cubeful bearoff db is used
>> for moneygame but not for matches.
>> But the differences that were spotted here were for the cubeless equities?
>>
>> Cheers,
>> Misja
>>
>> On Thu, Jun 25, 2009 at 9:00 PM, Christian
>>> The two-sided cubeful bearoff db is exact and used in preference of
>>> evalutation, but only for moneygame.
>>>
>>> Christian.
>>>
>>> On Fri, Jun 19, 2009 at 3:56 PM, Massimiliano
>>>>
>>>> Hi all,
>>>>
>>>> on a forum I've found this: same position (in 2-sided bearoff dB)
>>>> in money play and match play (3aw-3aw) shows different cubeless
>>>> equities. I tried to explain it but I run into some confusion.
>>>>
>>>> That's money play:
>>>>
>>>>     GNU Backgammon  Position ID: 6AUAADoDAAAAAA
>>>>                     Match ID   : UQkAAAAAAAAA
>>>>     +24-23-22-21-20-19------18-17-16-15-14-13-+  O: gnubg
>>>>  OO |          O  O  O |   |                  |  0 points
>>>>  OO |             O    |   |                  |
>>>>  OO |             O    |   |                  |
>>>>  OO |             O    |   |                  |
>>>>   O |                  |   |                  |
>>>>     |                  |BAR|                  |v
>>>>   X |                  |   |                  |
>>>>  XX |                  |   |                  |
>>>>  XX |          X       |   |                  |
>>>>  XX |          X     X |   |                  |  On roll
>>>>  XX |       X  X     X |   |                  |  0 points
>>>>     +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: MaX (Cube: 2)
>>>>
>>>> Hint shows this:
>>>>
>>>> Cube analysis
>>>> 2-ply cubeless equity  +0.4971
>>>>   0.7485 0.0000 0.0000 - 0.2515 0.0000 0.0000
>>>> Cubeful equities:
>>>> 1. Double, take         +0.9158
>>>> 2. Double, pass         +1.0000  ( +0.0842)
>>>> 3. No double            +0.7661  ( -0.1496)
>>>> Proper cube action: Redouble, take
>>>>
>>>> From eval (ctrl+E) I see (uninteresting parts removed):
>>>>
>>>> Match ID:        UQlgAAAAAAAA
>>>>
>>>> Evaluator:         Bearoff2
>>>>
>>>>              Player       Opponent
>>>> Position          880           912
>>>>
>>>>         Win     W(g)    W(bg)   L(g)    L(bg)   Equity    Cubeful
>>>> static: 0.7485  0.0000  0.0000  0.0000  0.0000   +0.4971   +0.7661
>>>>  1 ply: 0.7485  0.0000  0.0000  0.0000  0.0000   +0.4971   +0.7661
>>>>  2 ply: 0.7485  0.0000  0.0000  0.0000  0.0000   +0.4971   +0.7661
>>>>
>>>> Static, 1ply and 2ply figures are identical, which makes me think they all
>>>> come from the 2s bearoff dB (eval output is a bit confusing here).
>>>>
>>>> That's the same for match:
>>>>
>>>>     GNU Backgammon  Position ID: 6AUAADoDAAAAAA
>>>>                     Match ID   : UQlgAAAAAAAA
>>>>     +24-23-22-21-20-19------18-17-16-15-14-13-+  O: gnubg
>>>>  OO |          O  O  O |   |                  |  0 points
>>>>  OO |             O    |   |                  |
>>>>  OO |             O    |   |                  |
>>>>  OO |             O    |   |                  |
>>>>   O |                  |   |                  |
>>>>     |                  |BAR|                  |v 3 point match
>>>>   X |                  |   |                  |
>>>>  XX |                  |   |                  |
>>>>  XX |          X       |   |                  |
>>>>  XX |          X     X |   |                  |  On roll
>>>>  XX |       X  X     X |   |                  |  0 points
>>>>     +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: MaX (Cube: 2)
>>>>
>>>> Cube analysis
>>>> 2-ply cubeless equity  +0.4797 (Money:  +0.4797)
>>>>   0.7399 0.0000 0.0000 - 0.2601 0.0000 0.0000
>>>> Cubeful equities:
>>>> 1. Double, take         +0.9565
>>>> 2. Double, pass         +1.0000  ( +0.0435)
>>>> 3. No double            +0.7841  ( -0.1724)
>>>> Proper cube action: Redouble, take
>>>>
>>>>         Win     W(g)    W(bg)   L(g)    L(bg)   Equity    Cubeful
>>>> static: 0.7485  0.0000  0.0000  0.0000  0.0000   +0.4971   +0.8543
>>>>  1 ply: 0.7399  0.0000  0.0000  0.0000  0.0000   +0.4797   +0.8308
>>>>  2 ply: 0.7399  0.0000  0.0000  0.0000  0.0000   +0.4797   +0.7841
>>>>
>>>> The original question was: why the 2-ply cubeless GWC are different
>>>> between money and match ?
>>>> First answer was: it's using bearoff dB from money and not for match.
>>>> Objection was that gnubg could/should use the dB even for match, at
>>>> least for the cubeless GWC figures.
>>>>
>>>> Here I tried to explain that cubefull figures from the dB can only be
>>>> used in money play, but what about cubeless ? Are cubeless figures from
>>>> the dB used as a base for cubefull eval in match play ?
>>>>
>>>> Looking at the figures I would say yes: the static cubeless GWC for match
>>>> are exactly the ones you have in money. But they diverge at 1 and 2 ply.
>>>>
>>>> Am I right if I say that doing 2ply eval in match, gnubg needs to compute
>>>> a lot of 0ply cubeless evals and it takes them from the dB. The figures
>>>> are converted into 0ply cubeful (Janowski formula) and then
>>>> "backpropagated"
>>>> to get 2ply cubeful. 2ply cubeless is computed by inversing the Janowski
>>>> formula on 2ply cubeful figures.
>>>>
>>>> If all the above is true, I do see the objection coming: it's true that
>>>> what
>>>> matter are cubeful figures (and these cannot be taken from the dB in
>>>> match),
>>>> but why gnubg isn't showing the "right" cubeless GWC (the ones from the dB)
>>>> in match ?
>>>>
>>>> Side question: I tried to use bearoffdump. I manage to get the info putting
>>>> in the position ID:
>>>>
>>>> Bearoff database: gnubg_ts0.bd
>>>>
>>>>
>>>>  * On disk 2-sided bearoff database evaluator
>>>>    - generated by GNU Backgammon
>>>>    - up to 6 chequers on 6 points (924 positions) per player
>>>>    - database includes both cubeful and cubeless equities
>>>>    - number of reads: 0
>>>>
>>>>
>>>> Dump of position ID: 6AUAADoDAAAAAA
>>>>
>>>>              Player       Opponent
>>>> Position          880           912
>>>>
>>>> Cubeless equity               : +0.4971
>>>> Owned cube                    : +0.7661
>>>> Centered cube                 : +0.7451
>>>> Opponent owns cube            : +0.4579
>>>>
>>>> But I had no success in using the -n option (enter directly the
>>>> position indexes, 880 and 921): how is this supposed to work ?
>>>>
>>>> MaX.
>>>> _______________________________________________
>>>> Bug-gnubg mailing list
>>>> http://lists.gnu.org/mailman/listinfo/bug-gnubg
>>>>
>>>>
>>>
>>> _______________________________________________
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>>>
>>>
>>
>

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