Hi.

I actually have quite a few questions about Extreme Gammon but this one has been coming up a lot lately. I've transcribed a lot of books ("Pure Strategy", "501 Essential Backgammon Problems", "Cube like a boss, etc.) so I can use the xg files as sort of quizes and record my progress over time to see where I'm getting better and also where I'm just not learning the lesson. That's the context, here's the question.

I've been rolling out some positions to check the moves and I sometimes see XG "chooses" a move that is not rated the best. When I say "choose" I mean the move that has the little white logo thing on it (I think it's a cup of coffee or something?).

Here's an example:

XGID=-BA--BCA-----A----bdecBCa-:1:1:1:31:0:0:3:0:10

I rolled out the top three moves that XG came up with and it looks like this:

6/2 36.6% G:1.2% B:0% -0.496

23/22 13/10 36.9% G:1.0% B:0% -0.497

23/22 7/4 37.1% G:0.9% B:0% -0.502 (-0.005)

XG marks it's "choice" as the third move down (rated third best but it has the highest winning %).

So why does it do this and what does it mean? I have probably 20 or 30 positions where this happens so I'm not so concerned with the specific position but more with the general idea of XG "picking" a move that it doesn't rate the highest on equity.

I hope this make sense and I hope someone can answer.

XGs "choice" is the move that it preferred at eval, so if you do a RO and it overturns, the "choice" and correct play will be different. This is the same as how you, as a human, can get "outplay" markers for a move. XG at initial levle prefers something else then reevaluates at a higher level and likes your move.

Ahhhhh. That makes sense to me now. I'd always assumed XG would "pick" its move again once the rollout finished.

Thanks very much for your answer.