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52D-33E-41, analysis

Posted By: Nack Ballard
Date: Tuesday, 8 February 2011, at 9:58 p.m.

In Response To: 52D-33E-41 (Paul Weaver)


2O '2X ' '3X '3X ' ' '3O

 ' ' '2X '5O '4O ' '1O5X

52D-33E-41


I could not find a rollout for this third roll position, which is no surprise given that Opp's 52D-33 play is such a clear mistake: [A C30 B41 E41 N84] ~15***5.

However, I have imprinted on many reference positions that clue me in. Several years ago, I investigated (with Paul's help) some altered opening positions, giving the opponent various stronger anchors than the 24pt. There was a powerful theme rippling through them. I'll discuss a few with the 21pt to convey the idea.


2O ' ' ' '5X '3X ' ' '5O

 ' ' '2X '5O '3O ' ' '5X

Blue to play 64, 63, 62, 41 or 21


With a roll of 64 or 62, Z (reverse split, 24/20 13/7, or 24/22 13/7) is the best play by a significant margin. I think 63Z may have come out ahead as well, but even it didn't, the fact that it was close (even though it doesn't duplicate 3s) is noteworthy.

With a roll of 41, W (Wild, 24/20 6/5) was a big winner. I don't recall what happened with 21, but W (Wild, 24/22 6/5) was right in the mix as well.

As opening plays, 64Z, 63Z, 62Z, 41W and 21W are a "joke," being errors of .101, .060, .079, .051, and .100, respectively. By contrast, when you advance White's anchor from the 24pt to the 21pt (as diagrammed above), all five plays are relatively improved by about 100 millipoints: they all become "tied" or better.

There are a few valuable insights here. One is that it is a very strong tactic to slot in front of an advanced anchor; you should look for efficient opportunities to do so. It's not that the slotted point is more worthwhile to own; it's actually a bit less worthwhile because after you cover it is less effective as a blocking point against the higher anchor, and even if you are able to send back a third checker later, Opp will have that anchor as a landing spot. In more-than-ample compensation, however, Opp has fewer numbers to hit, and she must break her stronger anchor if she chooses to hit.

Secondly, when Opp is anchored, the incentive to move your own back checkers is increased (more on that in a minute.)

Thirdly, knowing exactly HOW much of an error a wrong opening play can often provide a vital reference. Here, for example, if you know that opening 41W is wrong by "only" .051 (or so), you are more likely to make the correct play in a position that is W-friendly. This principle holds true for the second and third roll positions, too, but the closer to the beginning of the game your reference point, the cleaner the basis of comparison.

[David, Stick and I like to set of a minimum of 5k for any early game plays we roll out. (In fact, David and I, and perhaps others, also prefer to see any money plays within .01 go to 62k, or within .02 to at least 31k, or within .03 to go to at least 15k.) If a play is summarily dropped just because it is almost certainly not "best," then it is much more difficult to derive well-defined reference points or to distinguish between real bot/ply differences and statistical noise.]

That brings us to Paul's posted position:


2O '2X ' '3X '3X ' ' '3O

 ' ' '2X '5O '4O ' '1O5X

52D-33E-41


All or most of us already know the answer must be W because of QF. But this position is solvable over the board. If the examples discussed earlier in this post have done their job, I imagine that the choice of P (Point, 11/7 8/7) or W (Wild, 24/20 6/5) already feels close to you. There are (a) Opp's 21pt anchor and (b) ace duplication that support the W play.

Now tack on four additional concepts. The first is that the 7pt becomes less valuable when Opp has an advanced anchor. On the surface it may seem paradoxical that the small-number blocking points in front of an anchor are less valuable to own, and yet you have greater motivation (more willingness) to slot them, but if you reread the sixth paragraph of this post it should help.

The second concept appears contrary and then rights itself. White has lost two of her 6pt spares to the 3pt. This is often a signal to Blue that he needn't hurry to split because those spares can no longer be used to make the primier 5pt or 4pt, and that more than compensates him for the 3pt (or especially the lowly 2pt) being in itself a blocking point. Here, though, Blue has no especially effective plan/hope for the offense; he is unlikely to win a priming battle if he stays back on the 24pt.

More importantly (though related), the third concept is that White has already accomplished what she needs to (gaining an advanced anchor) with her back checkers: she is now aching to unload her midpoint into the outer board and create builders for her 5pt and 4pt gaps. Splitting to the 20pt spoils White's immediate and primary aim.

Fourthly (though only supplementally), there is not only duplication of White's aces, but also if Blue gets hit somewhere then his own 6s and 3s (that are blocked from the roof) are diversified to cover or hit back on his 5pt.

The above analysis is for money. I don't think that Paul's –9–6 match score is likely to make a pivotal difference for this play.

Nack

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