Re: [Bug-gnubg] Need help on evaluating a position

[Carla Doumard]

Thanks to both for the useful answer and interesting analysis.

Happy New Year to all :-))
Carla

--- Original Message ---
> Nardy Pillards wrote:
> > I assume you use the Win32 GUI build.
> > 
> > Settings / Players: both human
> > Settings / Options /Dice: manual
> > 
> > In front of the names (bottom of screen) there 
> is a small checker.
> > Click on the one before your opponent's name, 
> so it will be his/her 
> > turn to roll the dice or use the cube.
> > Analyse / Hint (or Ctrl + H) will show you the 
> Hint about the cube.
> > Analyse / Evaluate the evaluation of the 
> position.
> 
> Why do you set the players to human and dice to 
> manual? I would just:
> 
> Click on the checker next to oppenents name (or 
> Game/Set Turn/<name of
> opponent>)
> Analyse/Hint
> 
> > By the way, if you have any advice about this 
> position, I would be happy to hear it.
> > For the record, he doubled, I took, redoubled 
> to 8, and rolled a 3 2, so lost.
> > 
> > I'd like to know if it was right to take or 
> not.
> > 
> > Thanks very much for your help, and happy neww 
> year to all :-)
> > 
> > Carla
> > 
> > The score (after 0 games) is: opponent 4, me 0 
> (match to 7 points)
> This is a very illustrative position - since it 
> a big problem gnubg has
> with automatic recubes. Here are the results of 
> 0-3 ply:
> 
> Cube analysis
> 0-ply cubeless MWC  88,54% (Money:  +0,793)
>   0,896 0,000 0,000 - 0,104 0,000 0,000
> Cubeful equities:
> 1. Double, pass         91,25%
> 2. Double, take         94,82%  (  3,57%)
> 3. No double            89,94%  ( -1,31%)
> Proper cube action: Redouble, pass
> 
> Cube analysis
> 1-ply cubeless MWC  88,54% (Money:  +0,793)
>   0,896 0,000 0,000 - 0,104 0,000 0,000
> Cubeful equities:
> 1. No double            89,70%
> 2. Double, pass         91,25%  (  1,55%)
> 3. Double, take         89,65%  ( -0,05%)
> Proper cube action: No redouble, take (3,4%)
> 
> Cube analysis
> 2-ply cubeless MWC  88,54% (Money:  +0,793)
>   0,896 0,000 0,000 - 0,104 0,000 0,000
> Cubeful equities:
> 1. No double            90,22%
> 2. Double, pass         91,25%  (  1,03%)
> 3. Double, take         89,65%  ( -0,57%)
> Proper cube action: No redouble, take (35,7%)
> 
> Cube analysis
> 3-ply cubeless MWC  88,54% (Money:  +0,793)
>   0,896 0,000 0,000 - 0,104 0,000 0,000
> Cubeful equities:
> 1. Double, take         89,65%
> 2. Double, pass         91,25%  (  1,60%)
> 3. No double            88,68%  ( -0,97%)
> Proper cube action: Redouble, take
> 
> Further plies gives same result.
> 
> And here is my explanation of what is happening:
> 
> 
> On 0-ply, gnubg doesn't see your recube to 8 - 
> so it calculates a "cube
> ownership value" which is much too low.
> 
> On 1-ply, gnubg see the recube - so it get's the 
> value of double-take
> accurate. It slightly misestimates the cube 
> ownership value of keeping the
> cube, though
> 
> On 2-ply, gnubg suddenly sees the possibility of 
> cubing on next roll - but
> not the recube to 8! Thus it advices you that 
> doubling now is a huge error.
> 
> On 3-ply, gnubg sees all the possible cube 
> action, and get's the same
> result as an exact rollout.
> 
> Note the two cases where gnubg get's it wrong: 
> It sees the cube to 4, but
> not that the recube to 8 is automatic.
> 
> My guess is that this pattern can be refound in 
> other similar positions.
> 
> -- 
> Nis Jorgensen
> IT Department
> Greenpeace International
> +31 6 1500 7413
>