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"Use Opening Books" -- turn on or off?

Posted By: Nack Ballard
Date: Wednesday, 11 October 2017, at 2:19 p.m.

In Response To: XG 'Book' Moves - authoritative? (Nack Ballard)





White is Player 2

score: 0
pip: 163
Unlimited Game
Jacoby Beaver
pip: 162
score: 0

Blue is Player 1
XGID=-b----E-C--AeD---b-dbA--A-:0:0:1:31:0:0:3:0:10

32S-31P-31


1.XG Roller++8/5 6/5eq: +0.003
Player:
Opponent:		50.02% (G:14.84% B:0.72%)
49.98% (G:14.43% B:0.71%)
2.XG Roller++24/21 11/10eq: -0.029 (-0.031)
Player:
Opponent:		48.50% (G:10.82% B:0.33%)
51.50% (G:9.47% B:0.32%)


I almost forgot to mention... 32S-31P-31, shown above, is diagrammed and analyzed on page 62 of Backgammon Openings. The superior play is to make the 5pt as illustrated in diagram A156 there. Its inferior rival is to anchor (with 24/21 11/10), which is shown in diagram A157 there but I trust you can visualize them both.

The position you asked about, 32Z-31P-31, appears as diagram A158 on the bottom of the same page and also in this post below. Again the superior play is to make the 5pt. What's interesting is that the inferior anchoring play in both A156 and A159 (above and below, here) end up with the identical A157 position (and an absolute ++ equity of –.029).

[The XGR++ evals show margins of .031 and .069 here. 5k rollouts refine those margins to .040 and .052, respectively.]

Now, suppose at some point the two moves made from 32S-31P-31 (above) end up as rolled out plays in XG's opening book. In that case, if you ask XG about 32Z-31P-31 (below) and have "Use Opening Book" turned on, it will give you an evaluated equity for 32Z-31P-31P (Point) and a rolled out equity for 32Z-31P-31@ (anchor). This will save you from having to roll out one of the plays (in the event you would have wanted to do a rollout).

This example demonstrates that there can be a benefit to having "Use Opening Book" turned on (that box unchecked). Not only will the whole rollout show up if the position has already been rolled out, but one or more transpositional plays might have already been rolled out.

That said, I leave that feature turned off for reasons I mentioned before (and turn it on only when wanting to see a specific book rollout or when I want to do a rollout and notice that a transpositional play exists that may have been pre-rolled). My purpose has been to illuminate the other side of the tradeoff so that you can better decide for yourself.

Nack





White is Player 2

score: 0
pip: 163
Unlimited Game
Jacoby Beaver
pip: 162
score: 0

Blue is Player 1
XGID=-b----E-C-A-eD---b-db-A-A-:0:0:1:31:0:0:3:0:10

32Z-31P-31


1.XG Roller++8/5 6/5eq: +0.041
Player:
Opponent:		50.83% (G:15.10% B:0.73%)
49.17% (G:14.29% B:0.64%)
2.XG Roller++24/21 22/21eq: -0.029 (-0.069)
Player:
Opponent:		48.50% (G:10.82% B:0.33%)
51.50% (G:9.47% B:0.32%)

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