Is there a method to figuring out these positions (and similar) over the board?

I split the checkers on the 20 point and it turns out to be very wrong. Do you pros consider these sorts of problems simple or complex? Do you take wild guesses, do you calculate, or do you act based on experience/references?

XGID=--BBCCB---------b-a-Cadeb-:0:0:1:61:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O | | X O O O O |
| O | | X O O O |
| | | X O O |
| | | O O |
| | | O |
| |BAR| |
| | | |
| | | |
| | | X X |
| | | X X X X X |
| | | X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 109 O: 53 X-O: 0-0
Cube: 1
X to play 61


eXtreme Gammon Version: 2.10

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, February 14, 2023 at 8:08:14 PM UTC-5, Robert Zimmerman wrote:

Is there a method to figuring out these positions (and similar) over the board?

I split the checkers on the 20 point and it turns out to be very wrong. Do you pros consider these sorts of problems simple or complex? Do you take wild guesses, do you calculate, or do you act based on experience/references?

XGID=--BBCCB---------b-a-Cadeb-:0:0:1:61:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O | | X O O O O |
| O | | X O O O |
| | | X O O |
| | | O O |
| | | O |
| |BAR| |
| | | |
| | | |
| | | X X |
| | | X X X X X |
| | | X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 109 O: 53 X-O: 0-0
Cube: 1
X to play 61

eXtreme Gammon Version: 2.10

I wouldn't call ~.050 'very wrong' generally. It's a mid size error at most, not even bloody red when you feed it into the bots. You need to understand how all of your opponent's rolls play next turn if you split versus if you don't split. OtB it's
time consuming so you should gain the experience of doing it at home. Then you'll understand similar positions in advance from having done this and also be able to do it much quicker and more accurately OtB.

Stick

--- SoupGate-Win32 v1.05
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On Tuesday, February 14, 2023 at 8:47:34 PM UTC-5, Stick Rice wrote:

On Tuesday, February 14, 2023 at 8:08:14 PM UTC-5, Robert Zimmerman wrote:

Is there a method to figuring out these positions (and similar) over the board?

I split the checkers on the 20 point and it turns out to be very wrong. Do you pros consider these sorts of problems simple or complex? Do you take wild guesses, do you calculate, or do you act based on experience/references?

XGID=--BBCCB---------b-a-Cadeb-:0:0:1:61:0:0:0:0:10

Score is X:0 O:0. Unlimited Game +13-14-15-16-17-18------19-20-21-22-23-24-+
| O O | | X O O O O |
| O | | X O O O |
| | | X O O |
| | | O O |
| | | O |
| |BAR| |
| | | |
| | | |
| | | X X |
| | | X X X X X |
| | | X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 109 O: 53 X-O: 0-0
Cube: 1
X to play 61

eXtreme Gammon Version: 2.10

I wouldn't call ~.050 'very wrong' generally. It's a mid size error at most, not even bloody red when you feed it into the bots. You need to understand how all of your opponent's rolls play next turn if you split versus if you don't split. OtB it's

time consuming so you should gain the experience of doing it at home. Then you'll understand similar positions in advance from having done this and also be able to do it much quicker and more accurately OtB.

Stick

Thank you. I was hoping someone would say there's a method that I'm ignorant of. Helps to know the truth.
Bob

--- SoupGate-Win32 v1.05
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On 2/14/2023 8:08 PM, Robert Zimmerman wrote:

Is there a method to figuring out these positions (and similar) over the board?

I split the checkers on the 20 point and it turns out to be very wrong. Do you pros consider these sorts of problems simple or complex? Do you take wild guesses, do you calculate, or do you act based on experience/references?

This is a type of position where you have to consider how each
of your opponent's next rolls play; going by intuition is not
going to be reliable.

But one general principle to remember is that splitting in order
to get a double shot is usually something that you only need to
consider when there's a good chance this will be your last chance
to hit a shot. Holding the anchor is usually a better strategy
when you're going to get more than one chance. Of course, this
observation doesn't help you all that much here, because this is
one of those cases where this could very well be your last chance.
So you still have to go through the different rolls.

---
Tim Chow

--- SoupGate-Win32 v1.05
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On Thursday, February 16, 2023 at 10:17:45 AM UTC-5, Timothy Chow wrote:

On 2/14/2023 8:08 PM, Robert Zimmerman wrote:

Is there a method to figuring out these positions (and similar) over the board?

I split the checkers on the 20 point and it turns out to be very wrong. Do you pros consider these sorts of problems simple or complex? Do you take wild guesses, do you calculate, or do you act based on experience/references?

This is a type of position where you have to consider how each
of your opponent's next rolls play; going by intuition is not
going to be reliable.

But one general principle to remember is that splitting in order
to get a double shot is usually something that you only need to
consider when there's a good chance this will be your last chance
to hit a shot. Holding the anchor is usually a better strategy
when you're going to get more than one chance. Of course, this
observation doesn't help you all that much here, because this is
one of those cases where this could very well be your last chance.
So you still have to go through the different rolls.

---
Tim Chow

Thanks, Tim. I fiddled around with some positions and, as you describe, you need to be at or approaching last chance. In nearly all cases that I've looked at, for splitting to be correct your point should be within three pips of the opponent's and the
opponent's home board should have at least open 4-5-6 points. I may use that as my rough guide to these positions so I don't lose a lot of time over the board. There is more complexity to my originally posted position, and I think it's probably best to
play safe in positions like that unless you have the time and aptitude to figure it out over the board.

Bob

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 2023-02-15, Robert Zimmerman <zimbrookside@gmail.com> wrote:

Is there a method to figuring out these positions (and similar) over
the board?

I split the checkers on the 20 point and it turns out to be very
wrong. Do you pros consider these sorts of problems simple or complex?
Do you take wild guesses, do you calculate, or do you act based on experience/references?

XGID=--BBCCB---------b-a-Cadeb-:0:0:1:61:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O | | X O O O O |
| O | | X O O O |
| | | X O O |
| | | O O |
| | | O |
| |BAR| |
| | | |
| | | |
| | | X X |
| | | X X X X X |
| | | X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 109 O: 53 X-O: 0-0
Cube: 1
X to play 61

There is an example of these positions in Michy's _Endgame Technique_
book. He calls them Amoeba Play.

As far rules of thumbs go, he writes that you should split when all the opponent's men you are holding are stacked on one point (a fairly common
case, but note that he doesn't write "only when...").

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Wednesday, February 15, 2023 at 1:08:14 AM UTC, Robert Zimmerman wrote:

Is there a method to figuring out these positions (and similar) over the board?

I split the checkers on the 20 point and it turns out to be very wrong. Do you pros consider these sorts of problems simple or complex? Do you take wild guesses, do you calculate, or do you act based on experience/references?

XGID=--BBCCB---------b-a-Cadeb-:0:0:1:61:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O | | X O O O O |
| O | | X O O O |
| | | X O O |
| | | O O |
| | | O |
| |BAR| |
| | | |
| | | |
| | | X X |
| | | X X X X X |
| | | X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 109 O: 53 X-O: 0-0
Cube: 1
X to play 61

eXtreme Gammon Version: 2.10

I would have split too. As others have said, this could readily
be resolved by looking at all 1296 sequences (counted with multiplicity),
but very few people (if any) could do this OTB.
BTW, I would think that there are people who have the ability to learn how to look at
all 1296 sequences accurately OTB and make the correct assessment.
It's just that people with that type of calculation and visualization skill don't usually play backgammon.

Paul

--- SoupGate-Win32 v1.05
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On Wednesday, March 8, 2023 at 4:48:36 PM UTC-5, Philippe Michel wrote:

On 2023-02-15, Robert Zimmerman <zimbro...@gmail.com> wrote:

Is there a method to figuring out these positions (and similar) over
the board?

I split the checkers on the 20 point and it turns out to be very
wrong. Do you pros consider these sorts of problems simple or complex?
Do you take wild guesses, do you calculate, or do you act based on experience/references?

XGID=--BBCCB---------b-a-Cadeb-:0:0:1:61:0:0:0:0:10

Score is X:0 O:0. Unlimited Game +13-14-15-16-17-18------19-20-21-22-23-24-+
| O O | | X O O O O |
| O | | X O O O |
| | | X O O |
| | | O O |
| | | O |
| |BAR| |
| | | |
| | | |
| | | X X |
| | | X X X X X |
| | | X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 109 O: 53 X-O: 0-0
Cube: 1
X to play 61

There is an example of these positions in Michy's _Endgame Technique_
book. He calls them Amoeba Play.

As far rules of thumbs go, he writes that you should split when all the opponent's men you are holding are stacked on one point (a fairly common case, but note that he doesn't write "only when...").

Thanks for the info. That book is on the wish list.
I've concluded, and I could certainly be off the mark, that you should split only when there is one stack of 2 checkers in front of you, at a distance no greater than 3 pips from you, and no opponent blots in range. Not calculated, just empirical
evidence.

Bob

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 2023-03-09, Robert Zimmerman <zimbrookside@gmail.com> wrote:

I've concluded, and I could certainly be off the mark, that you should
split only when there is one stack of 2 checkers in front of you, at a distance no greater than 3 pips from you, and no opponent blots in
range. Not calculated, just empirical evidence.

The "2 checkers" part looks suspect.

Suppose there are 3 checkers: the split works immediately if the
opponent rolls 2 large numbers. That's about half as likely as the
large+small combinations against which a stack of 2 is vulnerable but
that may already be enough. Moreover you are already split if another combination strips it down to 2 (while you may not roll a small number
to split next roll if you had waited).

As the number of checkers raise the main favourable event is pushed in
the future and the risks of a crushing small doublet add up but
splitting against 3 should still be fine.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Thursday, March 9, 2023 at 3:54:10 PM UTC-5, Philippe Michel wrote:

On 2023-03-09, Robert Zimmerman <zimbro...@gmail.com> wrote:

I've concluded, and I could certainly be off the mark, that you should split only when there is one stack of 2 checkers in front of you, at a distance no greater than 3 pips from you, and no opponent blots in
range. Not calculated, just empirical evidence.

The "2 checkers" part looks suspect.

Suppose there are 3 checkers: the split works immediately if the
opponent rolls 2 large numbers. That's about half as likely as the large+small combinations against which a stack of 2 is vulnerable but
that may already be enough. Moreover you are already split if another combination strips it down to 2 (while you may not roll a small number
to split next roll if you had waited).

As the number of checkers raise the main favourable event is pushed in
the future and the risks of a crushing small doublet add up but
splitting against 3 should still be fine.

Yes, you're totally right. Thanks for that. And I should qualify what I said about the points being 3 pips or less apart. Moving the two points that are opposed to each other into the outfield and varying blots in the opponent's home board generated
occasions where the points could be 4 or 5 pips apart, but they were rare. N.B. I did NOT study this extensively, so take it with a pound of salt. Or don't take it at all. :)

Bob

--- SoupGate-Win32 v1.05
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