XGID=bBBBBBB--------AbbcccB----:1:1:1:00:0:4:3:0:10
X:Daniel O:eXtremeGammon

Score is X:0 O:4. Unlimited Game, Jacoby Beaver
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O O | | O O X |
| O O O | | O O X |
| O | | O O |
| | | |
| | | |
| |BAR| |
| | O | |
| | O | |
| | | | +---+
| | | X X X X X X | | 2 |
| | | X X X X X X | +---+
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 99 O: 138 X-O: 0-4
Cube: 2, X own cube
X on roll, cube action

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On 4/22/2022 5:53 PM, peps...@gmail.com wrote:

XGID=bBBBBBB--------AbbcccB----:1:1:1:00:0:4:3:0:10
X:Daniel O:eXtremeGammon

Score is X:0 O:4. Unlimited Game, Jacoby Beaver
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O O | | O O X |
| O O O | | O O X |
| O | | O O |
| | | |
| | | |
| |BAR| |
| | O | |
| | O | |
| | | | +---+
| | | X X X X X X | | 2 |
| | | X X X X X X | +---+
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 99 O: 138 X-O: 0-4
Cube: 2, X own cube
X on roll, cube action

There are a lot of positions that look similar to this one, but
small changes can make a big difference to the evaluation, so I
would hesitate to call this position "standard."

It looks like D/P to me. If X rolls an immediate 6 then clearly
O's position is a massive drop and possibly TG for X. But what
if X doesn't roll a 6? It will typically take X a couple of rolls
to start crunching his board, and even then O might not enter for
a while. All this gives X extra time to roll a 6, and once he
rolls a 6, he has more time to roll another 6. And even if things
turn around, O has work to do. She has only a two-point board,
and X will generally still have a reasonably strong board even if
he has started to crunch. If O hits loose and X hits back, then
X can quickly regain the upper hand. Given that X wins a lot of
gammons from this position, I don't think O can take.

On the other hand, it also doesn't look TG to me. If X doesn't
roll an immediate 6 then it might no longer be a pass.

---
Tim Chow

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On Saturday, April 23, 2022 at 9:30:16 PM UTC+1, Tim Chow wrote:

On 4/22/2022 5:53 PM, peps...@gmail.com wrote:

XGID=bBBBBBB--------AbbcccB----:1:1:1:00:0:4:3:0:10
X:Daniel O:eXtremeGammon

Score is X:0 O:4. Unlimited Game, Jacoby Beaver +13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O O | | O O X |
| O O O | | O O X |
| O | | O O |
| | | |
| | | |
| |BAR| |
| | O | |
| | O | |
| | | | +---+
| | | X X X X X X | | 2 |
| | | X X X X X X | +---+
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 99 O: 138 X-O: 0-4
Cube: 2, X own cube
X on roll, cube action

There are a lot of positions that look similar to this one, but
small changes can make a big difference to the evaluation, so I
would hesitate to call this position "standard."

It looks like D/P to me. If X rolls an immediate 6 then clearly
O's position is a massive drop and possibly TG for X. But what
if X doesn't roll a 6? It will typically take X a couple of rolls
to start crunching his board, and even then O might not enter for
a while. All this gives X extra time to roll a 6, and once he
rolls a 6, he has more time to roll another 6. And even if things
turn around, O has work to do. She has only a two-point board,
and X will generally still have a reasonably strong board even if
he has started to crunch. If O hits loose and X hits back, then
X can quickly regain the upper hand. Given that X wins a lot of
gammons from this position, I don't think O can take.

On the other hand, it also doesn't look TG to me. If X doesn't
roll an immediate 6 then it might no longer be a pass.

Can you be a bit more specific about which rolls you see as market gainers?

Paul

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On 4/23/2022 4:33 PM, peps...@gmail.com wrote:

Can you be a bit more specific about which rolls you see as market gainers?

Not sure exactly, but certainly 55, and probably if X rolls
a 9 or an 8. What if X rolls a 6 or a 7? I don't know. These
types of positions are typically very sensitive to moving the
outfield checker by just a couple of pips, so it's hard to be
confident.

MCG had a GammonVillage article or two about these types of closeout-v-fiveprime positions. As I recall, he focused on
positions with 1 checker back and 1 checker closed out, so one
would have to be cautious about making inferences about positions
like this one with 2 checkers back and 2 checkers closed out, but
what I remember is that if you had one spare as far back as possible
then it was a pass, and if you moved it around to be close to the
home board then it was a take. But the crossover point could
depend sensitively on other seemingly "minor" features of the
position.

---
Tim Chow

--- SoupGate-Win32 v1.05
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On 4/23/2022 4:46 PM, I wrote:

MCG had a GammonVillage article or two about these types of closeout-v-fiveprime positions.  As I recall, he focused on
positions with 1 checker back and 1 checker closed out, so one
would have to be cautious about making inferences about positions
like this one with 2 checkers back and 2 checkers closed out

I just went to the GammonVillage website to re-read MCG's article.
However, I couldn't find it. I don't know if the website has just
been reorganized, or if the online magazine has been discontinued.
Luckily, I saved a copy of MCG's article, so you can read it here
(not formatted very well, but legible):

http://alum.mit.edu/www/tchow/cg/mcg10.pdf

I guess GammonVillage owns the copyright to this article, so if they
complain, I'll take it down. But in the meantime, I see that I
failed to remember that MCG considered almost exactly your position
in the article. If you scroll to the very end of the article, you'll
see what I mean.

---
Tim Chow

--- SoupGate-Win32 v1.05
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On Saturday, April 23, 2022 at 10:53:04 PM UTC+1, Tim Chow wrote:

On 4/23/2022 4:46 PM, I wrote:

MCG had a GammonVillage article or two about these types of closeout-v-fiveprime positions. As I recall, he focused on
positions with 1 checker back and 1 checker closed out, so one
would have to be cautious about making inferences about positions
like this one with 2 checkers back and 2 checkers closed out

I just went to the GammonVillage website to re-read MCG's article.
However, I couldn't find it. I don't know if the website has just
been reorganized, or if the online magazine has been discontinued.
Luckily, I saved a copy of MCG's article, so you can read it here
(not formatted very well, but legible):

http://alum.mit.edu/www/tchow/cg/mcg10.pdf

I guess GammonVillage owns the copyright to this article, so if they complain, I'll take it down. But in the meantime, I see that I
failed to remember that MCG considered almost exactly your position
in the article. If you scroll to the very end of the article, you'll
see what I mean.

Thanks for this. I'm reading the article too.
I disagree with this: "With a checker on the 16 and a checker on the 4, we have a definite
take. What happened? It isn't obvious."
But it's very obvious (to me). Firstly, the action didn't move a trillion light years.
We went from an ultra-marginal drop/take to a 0.961 take.
But why did we move at all? Well, duh! It's all about the EPC.
A checker on the 10 point is likely to move off the board with less wastage than a checker on the 4 point.
So 16/4 gives us less timing, not much less (perhaps a fraction of a pip) but 0.04 isn't terribly large here.
Some things are mysterious (for example human consciousness) but I don't think this particular piece
of variantizing is one of them.

Wow, the final position is uncannily similar. It certainly vindicates your view that, if we don't roll a 6, we often gain
market and very often can't even double.
However, the position is actually TG, according to XG's rollout. I did keep XG's rollout but it's on another computer.
I'll show it to you later.

Paul

--- SoupGate-Win32 v1.05
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On Saturday, April 23, 2022 at 10:53:04 PM UTC+1, Tim Chow wrote:

On 4/23/2022 4:46 PM, I wrote:

MCG had a GammonVillage article or two about these types of closeout-v-fiveprime positions. As I recall, he focused on
positions with 1 checker back and 1 checker closed out, so one
would have to be cautious about making inferences about positions
like this one with 2 checkers back and 2 checkers closed out

I just went to the GammonVillage website to re-read MCG's article.
However, I couldn't find it. I don't know if the website has just
been reorganized, or if the online magazine has been discontinued.
Luckily, I saved a copy of MCG's article, so you can read it here
(not formatted very well, but legible):

http://alum.mit.edu/www/tchow/cg/mcg10.pdf

I guess GammonVillage owns the copyright to this article, so if they complain, I'll take it down. But in the meantime, I see that I
failed to remember that MCG considered almost exactly your position
in the article. If you scroll to the very end of the article, you'll
see what I mean.

I think it's a weakness in the article that TG isn't mentioned at all.
Here is the rollout. Although the position is TG, I wouldn't say the
rollout is TG -- in fact, it may not be G enough. I didn't do anything with the
settings.

Paul

Analyzed in Rollout
No redouble
Player Winning Chances: 69.78% (G:50.92% B:0.37%)
Opponent Winning Chances: 30.22% (G:4.95% B:0.17%)
Redouble/Take
Player Winning Chances: 70.13% (G:51.24% B:0.35%)
Opponent Winning Chances: 29.87% (G:5.05% B:0.18%)

Cubeless Equities: No Double=+0.857, Double=+1.732

Cubeful Equities:
No redouble: +1.045
Redouble/Take: +1.459 (+0.414)
Redouble/Pass: +1.000 (-0.045)

Best Cube action: Too good to redouble / Pass
Percentage of wrong take needed to make the double decision right: 9.8%

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On 4/23/2022 5:52 PM, I wrote:

I just went to the GammonVillage website to re-read MCG's article.
However, I couldn't find it.  I don't know if the website has just
been reorganized, or if the online magazine has been discontinued.

It turns out that the website was reorganized. Here's the link, for
those who have a GV subscription.

https://www.gammonvillage.com/backgammon/magazine/article_display.cfm?resourceid=6259

I don't think that there has been any fresh content for a while, so
I wouldn't be surprised if they discontinue the magazine at some point.

---
Tim Chow

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