Slot or not?

[Timothy Chow]

XGID=-dBBB-BD-----A--bb-cbB-b--:1:-1:1:42:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O O X O | +---+
| O O | | O O X O | | 2 |
| | | O | +---+
| | | |
| | | |
| |BAR| |
| | | |
| X | | O |
| X | | O |
| X | | X X X X O |
| X | | X X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 113 O: 162 X-O: 0-0
Cube: 2, O own cube
X to play 42

---
Tim Chow

[Robert Zimmerman]

I would play 13/11 7/3 to cover 24/20, -/- played by O's back checker. O's 64 would hit us, but not much lost in the transaction. O's position is so tenuous that I don't think slotting is useful. I don't want to waste time on the bar and miss the opportunity to take advantage of O's breaking up.
Bob

[Timothy Chow]

The trouble with not slotting is that the alternatives are destructive,
either stacking up another checker on the bar point, or putting a
checker out of play with 7/3. It might seem that X has a big enough
advantage that he should be playing safe, but making his 5pt would be
a big improvement, while getting hit is not irrecoverable.

If the roll were 21 instead of 42 (see variant), then the safe play of
13/11 7/6 would be a viable candidate (though XG still slightly prefers
slotting).

1. Rollout¹ 13/9 7/5 eq:+0.958
Player: 80.17% (G:42.64% B:5.08%)
Opponent: 19.83% (G:4.30% B:0.20%)
Confidence: ±0.008 (+0.950..+0.967) - [100.0%]

2. Rollout¹ 13/11 7/3 eq:+0.753 (-0.205)
Player: 74.81% (G:36.24% B:4.45%)
Opponent: 25.19% (G:5.05% B:0.20%)
Confidence: ±0.009 (+0.744..+0.762) - [0.0%]

3. Rollout¹ 13/7 eq:+0.736 (-0.222)
Player: 74.87% (G:34.86% B:4.14%)
Opponent: 25.13% (G:4.82% B:0.15%)
Confidence: ±0.009 (+0.727..+0.745) - [0.0%]

4. Rollout¹ 7/5 7/3 eq:+0.705 (-0.253)
Player: 73.63% (G:36.18% B:4.36%)
Opponent: 26.37% (G:6.42% B:0.34%)
Confidence: ±0.008 (+0.697..+0.714) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

-------
Variant
-------

XGID=-dBBB-BD-----A--bb-cbB-b--:1:-1:1:12:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O O X O | +---+
| O O | | O O X O | | 2 |
| | | O | +---+
| | | |
| | | |
| |BAR| |
| | | |
| X | | O |
| X | | O |
| X | | X X X X O |
| X | | X X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 113 O: 162 X-O: 0-0
Cube: 2, O own cube

X to play 12

1. Rollout¹ 7/6 7/5 eq:+0.961
Player: 80.47% (G:42.34% B:4.84%)
Opponent: 19.53% (G:4.56% B:0.25%)
Confidence: ±0.008 (+0.953..+0.969) - [99.9%]

2. Rollout¹ 13/11 7/6 eq:+0.943 (-0.018)
Player: 80.08% (G:41.04% B:5.00%)
Opponent: 19.92% (G:3.82% B:0.16%)
Confidence: ±0.008 (+0.934..+0.951) - [0.1%]

3. Rollout¹ 13/12 7/5 eq:+0.938 (-0.023)
Player: 80.00% (G:41.86% B:4.68%)
Opponent: 20.00% (G:4.63% B:0.23%)
Confidence: ±0.009 (+0.929..+0.947) - [0.0%]

4. Rollout¹ 13/10 eq:+0.859 (-0.102)
Player: 78.12% (G:38.46% B:4.54%)
Opponent: 21.88% (G:4.38% B:0.19%)
Confidence: ±0.008 (+0.851..+0.867) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

---
Tim Chow

[Philippe Michel]

On 2023-03-24, Timothy Chow <tchow...@yahoo.com> wrote:
> XGID=-dBBB-BD-----A--bb-cbB-b--:1:-1:1:42:0:0:0:0:10
>
> Score is X:0 O:0. Unlimited Game
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | X O O | | O O X O | +---+
> | O O | | O O X O | | 2 |
> | | | O | +---+
> | | | |
> | | | |
> | |BAR| |
> | | | |
> | X | | O |
> | X | | O |
> | X | | X X X X O |
> | X | | X X X X O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 113 O: 162 X-O: 0-0
> Cube: 2, O own cube
> X to play 42
>
> The trouble with not slotting is that the alternatives are destructive,
> either stacking up another checker on the bar point, or putting a
> checker out of play with 7/3. It might seem that X has a big enough
> advantage that he should be playing safe, but making his 5pt would be
> a big improvement, while getting hit is not irrecoverable.

I'm not sure "getting hit is not irrecoverable" (while certainly true)
is the most accurate reason to split.

The most important point is probably that a 4 for the opponent is a very
good roll whether it hits a slot or not. The slot is just not that
costly when it fails.

> If the roll were 21 instead of 42 (see variant),

Then X has more builders aimed at the 5 point and retains some outfield
control so most non-hitting 4s are not as strong than after 42.

[MK]

On March 29, 2023 at 4:30:38 PM UTC-6, Philippe Michel wrote:

> On 2023-03-24, Timothy Chow <tchow...@yahoo.com> wrote:

>> XGID=-dBBB-BD-----A--bb-cbB-b--:1:-1:1:42:0:0:0:0:10

>> X to play 42

Since I found this position interesting and used
it in another thread, I may as well comment on it.

https://groups.google.com/g/rec.games.backgammon/c/Z1QsqqGbTsw/m/x-wV5kisBAAJ

>> ..... or putting a checker out of play with 7/3.

The 4th checker on the 7-point is already the
most useless one anyway and after 7/3 it's
not completely out of play either.

>> It might seem that X has a big enough
>> advantage that he should be playing safe,

Not just it seems so but it is so.

>> making his 5pt would be a big improvement,

There is no need to rush to make it. With O's
4 checkers on X's 1-point, that can wait.

> I'm not sure "getting hit is not irrecoverable"

> ..... is the most accurate reason to split.

> The slot is just not that costly when it fails.

Hard to understand why you are objecting to
Tim and what you are arguing for instead...?

Anyway, I think Zimmer got this one right. I
would play 13/11 7/3 also and the "clinical
rollouts" I have done at the link above show
that it's slightly better than 13/9 7/5 (or at
least not any worse).

MK