2a 5a 64 to play - two obvious choices, but which is better?

[Walt]

XGID=-aBAB-C-B-A-dC---bbdA--b--:0:0:1:64:3:0:0:5:10

X:You O:O
Score is X:3 O:0 5 pt.(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X O |
| X O O | | O O |
| X | | O |
| | | O |
| | | |
| |BAR| |
| | | |
| O | | |
| O | | X |
| O X | | X X X |
| O X X | | X X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 118 O: 134 X-O: 3-0/5
Cube: 1
X to play 64

[Bradley K. Sherman]

Walt <walt_...@yahoo.com> wrote:
>Score is X:3 O:0 5 pt.(s) match.
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | X O O | | O X O |
> | X O O | | O O |
> | X | | O |
> | | | O |
> | | | |
> | |BAR| |
> | | | |
> | O | | |
> | O | | X |
> | O X | | X X X |
> | O X X | | X X X X O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+

> X:118 O:134, Cube:1, X to play 64

20/10 for me just to clean up, but 13/3 has its point.

--bks

[Freeven]

I'd play 20/10. My thinking is that escaping is the harder problem to
solve and that, if I'm not hit on the 3pt next turn, it's usually fairly
smooth sailing from there.

[badgolferman]

I'll play 20/10. There's more upside to escaping than closing the
3-point. If the blot is hit then we're pretty much back where we
started, but if O misses then he's finished.

[peps...@gmail.com]

20/10. Anti-Waltishly, I'll say that I'm making the same play as everyone else for much the same reasons. But I do have something to add. Clearly X doesn't want to be hit. Therefore, one of the reasons I want to follow the dictates of fashion is that this play leaves far fewer shots (11/36) than the reasonable alternatives. Even if we take the brave stand that we don't mind being hit loose on O's 5 point, there are plenty of pointing numbers to be scared of. I'm old enough to have experienced the non-child-friendly years where angry teachers would scold while pointing fingers at us. Being pointed at in backgammon is about as congenial.

Paul Epstein

[Tim Chow]

I play 20/10 like everyone else. We have a big race lead and want to
convert into a race. That means escaping the back checker.

I expect that 13/3 will win and lose more gammons than 20/10; making
another home-board point should increase gammons wins, and leaving a
straggler in O's home board (not to mention two blots) will lose more
gammons. I also expect 13/3 to lose more games. At gammon go,
perhaps 13/3 is better, but I have my doubts. Anyway, leading 2a5a,
we typically favor non-gammonish plays.

---
Tim Chow

[Walt]

I see that everyone other than me had an easy time with this since I
incorrectly covered the 3 point. A consistent flaw in my play is to
overvalue permanent assets and not make the better tactical play. Here,
a fourth homeboard point is a permanent asset while the ten is just a
waystation which we'll just have to clear later. But that doesn't
outweigh the immediate tactical advantage of escaping the runner.

A recent thread posted by Tim on bgonline.org dealt with pointing vs
Pottling*. Someone said something to the effect that when you correctly
Pottle, and are missed, that should be the end of it. You should have a
high probability of completing your escape, and entering a game where
you are favored not to be hit again.

I think that's applicable here, even though it's not the runner that's
in danger of being hit. After 20/10, if O doesn't roll a deuce then X
is in very good shape. There's also the fact that after covering the 3
O has 13 shakes that either hit the outfield blot or point on the head
of the straggler. That's 2 more than hit on the 3.


* see http://www.bkgm.com/gloss/lookup.cgi?pottle+s+law

XGID=-aBAB-C-B-A-dC---bbdA--b--:0:0:1:64:3:0:0:5:10

X:Player 1 O:Player 2

Score is X:3 O:0 5 pt.(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X O |
| X O O | | O O |
| X | | O |
| | | O |
| | | |
| |BAR| |
| | | |
| O | | |
| O | | X |
| O X | | X X X |
| O X X | | X X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 118 O: 134 X-O: 3-0/5
Cube: 1
X to play 64

1. XG Roller++ 20/10 eq:+0.595
Player: 67.62% (G:16.37% B:0.26%)
Opponent: 32.38% (G:6.58% B:0.18%)

2. XG Roller++ 13/3 eq:+0.538 (-0.056)
Player: 64.42% (G:22.78% B:0.61%)
Opponent: 35.58% (G:7.70% B:0.25%)

3. 2-ply 20/14 10/6 eq:+0.492 (-0.102)
Player: 64.82% (G:13.08% B:0.16%)
Opponent: 35.18% (G:6.42% B:0.21%)

4. 2-ply 20/14 13/9 eq:+0.379 (-0.215)
Player: 61.71% (G:13.53% B:0.18%)
Opponent: 38.29% (G:9.68% B:0.62%)

5. 1-ply 20/16 10/4 eq:+0.228 (-0.366)
Player: 58.25% (G:15.93% B:0.28%)
Opponent: 41.75% (G:9.81% B:0.29%)


eXtreme Gammon Version: 2.10, MET: Kazaross XG2


--
//Walt

[Walt]

Tim suggested that 13/3 might be right at gammon go, so here's XGR++ for
that score.



XGID=-aBAB-C-B-A-dC---bbdA--b--:0:0:1:64:0:1:1:2:10

X:Player 1 O:Player 2

Score is X:0 O:1 2 pt.(s) match.

+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X O |
| X O O | | O O |
| X | | O |
| | | O |
| | | |
| |BAR| |
| | | |
| O | | |
| O | | X |
| O X | | X X X |
| O X X | | X X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+

Pip count X: 118 O: 134 X-O: 0-1/2 Crawford

Cube: 1
X to play 64

1. XG Roller++ 13/3 eq:+0.714
Player: 63.75% (G:21.94% B:0.34%)
Opponent: 36.25% (G:8.06% B:0.36%)

2. XG Roller++ 20/10 eq:+0.663 (-0.051)
Player: 67.48% (G:15.67% B:0.17%)
Opponent: 32.52% (G:6.22% B:0.20%)

[peps...@gmail.com]

On Thursday, May 16, 2013 2:50:08 PM UTC+1, Walt wrote:
...

> I see that everyone other than me had an easy time with this since I
>
> incorrectly covered the 3 point.

...

No, we were just lucky. Also, I don't think any of us Walted so most of us are probably just following what the other Bloomberg newsreaders said.

Also, at 0.05 discrepancy between the plays, the issue seems somewhat marginal. A great multi-tasking trick is available here where we can Chow the position and candlestick at the same time, by moving O's two checkers on the 8 point to the 7 point.
That would probably make you correct to cover the 3 at both match scores.

Paul Epstein