[Bug-gnubg] double/beaver with table stakes.

[bob koca]

 
 
  Your idea of setting up O to kill gammons with a cube to 8 inorder to find a correct double/beaver if there are table stakes is good.
You seem to think the existence of such a position would be surprising to many but of course if you change the rules by introducing
table stakes new things might happen.
  Your position does not succeed in your quest though. It is not a double and doubling would actually be a big error theoretically (if opponent does not
know to beaver then it would be practically correct play). If there is a double then opponent could beaver. It is not optimal
but the oppponent could just always double next shake to 8 giving a position in which the cube is out of play and gammons/backgammons
don't count extra. The opponent could stay to the last checker going for the win. It is close to a 50-50 position then. Clearly X could do better
by holding the cube and having the bonus wins count.
 
Bob Koca

> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 23 Nov 2008 12:13:00 +0100
> From: "Thomas Koch" <address@hidden>
> Subject: [Bug-gnubg] table stakes beaver
> To: "address@hidden" <address@hidden>
> Message-ID:
> <address@hidden>
> Content-Type: text/plain; charset="iso-8859-1"
>
> In order to analyse positions with table stakes using gnubg, I put together
> a special met (http://page.mi.fu-berlin.de/tkoch/Backgammon/limit8.xml). Now
> I was wondering if this position
>
> X on roll, cube decision?
>
> GNU Backgammon Position ID: bNsIADa8HQAAAA
> Match ID : cAkAAAAAAAAA
> +24-23-22-21-20-19------18-17-16-15-14-13-+ O: Alice
> | O O O O | | O O | 0 points
> | O O O O | | O |
> | | | |
> | | | |
> | | | |
> | |BAR| |v (Cube: 1)
> X | | | |
> X | X | | |
> X | X X | | |
> X | O O X X X | | | On roll
> XX | O O X X X | | | 0 points
> +-1--2--3--4--5--6-------7--8--9-10-11-12-+ X: Bob
> Pip counts: O 154, X 35
>
> Output generated Sat Nov 22 19:34:37 2008
> by GNU Backgammon 0.16-devel (Text Export version 1.76)
>
> is a correct double/beaver even without Jacobyrule if the table stakes are
> set to 8 times the initial stakes (it is on snowie 3ply)!? But of course
> using a met makes gnubg work in match mode so beavers are not allowed. Is
> there a way to allow for beavers even in a match? If not, how can I deduce
> from the results of the rollout if a beaver would be correct?
>
> Cube analysis
> Rollout cubeless equity +0.498 (Money: +0.499)
>
> Cubeful equities:
> 1. Double, take +0.594
> 2. Double, pass +1.000 ( +0.406)
> 3. No double +0.520 ( -0.073)
> Proper cube action: Double, take
> Rollout details:
> Centered 1-cube:
> 0.538 0.295 0.129 - 0.462 0.000 0.000 CL +0.498 CF +0.520
> [0.003 0.002 0.002 - 0.003 0.000 0.000 CL 0.008 CF 0.017]
> Player Alice owns 2-cube:
> 0.553 0.295 0.136 - 0.447 0.000 0.000 CL +1.067 CF +0.594
> [0.004 0.003 0.002 - 0.004 0.000 0.000 CL 0.018 CF 0.027]
>
> Thanks!
>
> Thomas Koch
>
>
> --
> Backgammon in Berlin: http://berlinbg.wordpress.com
> Der Backgammon Blog: http://graswurzelbackgammon.wordpress.com
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> End of Bug-gnubg Digest, Vol 72, Issue 16
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