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Question about 4 ply XG cube rollouts

Posted By: eXtreme Gammon
Date: Thursday, 31 December 2009, at 6:44 p.m.

In Response To: Question about 4 ply XG cube rollouts (David Rockwell)

David,

First, XG use ply as Snowie does.

You are trying to apply the human way to see things to what computers do. But computers are dumb so they cannot apply the same principal than human do.

When XG evaluates a cube decision, 2 positions are analyzed: one with cube untouched and one with the cube doubled and own by the opponent. For a N-ply The evaluation of each choice is made by looking ahead all possible dice for N-1 moves.

The computer does not consider market losing sequence as a human does. They will be factored in the evaluation because for these at the 2nd look ahead the evaluation (for the "no Double" line) will be +1.000 (D/D) while for the "Double" line the equity will be greater than 1.000.

Now, when using a 3 ply, it means the position when you get to choose to double or not will be analyzed in 1-ply (Neural Network output, so cubeless but converted to cubeful using Janowski formulae).

If you use 4-ply the next cube action will use a 2-ply (meaning averaging all 21 dice resulting best moves in 1-ply) which is more accurate (for XG)

So from a computer point a view you cannot say “Doubling is inherently a 3 ply decision” as they do not have this concept.

For Rollouts each games is play exactly the same way that if you were playing it using the software.

I hope this answered your question

Xavier Dufaure de Citres

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