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BGonline.org Forums
Calculating Cube Efficiency from Rollouts/Evaluations
Posted By: Rick Janowski
Date: Saturday, 12 January 2013, at 10:30 a.m.
I was asked recently on how cube efficiency factors can be estimated from rollout data, and thought I would share this information. For unlimited games, the cube efficiencies for both players may be calculated from rollout or evaluation data as follows:
For the player on roll, x1 = (Eo – Ecl) / p (this is the cube efficiency for no double)
For the player not on roll, x2 = (Ecl – Eu) / (1-p) (this is the cube efficiency for double-take)
Where,
x1 and x2 are the cube-efficiency factors for the two players
p is the cubeless winning probability for the player on roll
Ecl is the cubeless equity
Eo is the cube-owned equity (holding a theoretical 1-cube)
Eu is the cube-unavailable equity (holding a theoretical 1-cube).Usually you need to take 50% of equity value from the rollout/evaluation as normally the output value assumes a 2-cube)
x1 may also be estimated from centred-cube equities, Ec, but it is quite complex and convoluted. It’s far easier and just as accurate to instead derive from a position where the cube has been set as owned by the roller, even if this is not actually the case.
It is interesting to note that XG 1-ply evaluations normally assume values of x1 and x2 of 0.705 unless the position is a backgame, when the higher value of 0.850 is assumed.
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