XGID=-aADCCC--------a----c-dccA:1:-1:1:63:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O | | O O O O | +---+
| | | O O O O | | 2 |
| | | O O O O | +---+
| | | O |
| | X | |
| |BAR| |
| | | |
| | | X |
| | | X X X X |
| | | X X X X |
| | | X X X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 84 O: 70 X-O: 0-0
Cube: 2, O own cube
X to play 63

---
Tim Chow

XGID=-aADCCC--------a----c-dccA:1:-1:1:63:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O | | O O O O | +---+
| | | O O O O | | 2 |
| | | O O O O | +---+
| | | O |
| | X | |
| |BAR| |
| | | |
| | | X |
| | | X X X X |
| | | X X X X |
| | | X X X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 84 O: 70 X-O: 0-0
Cube: 2, O own cube
X to play 63

Most people would not hit here, because the downside of getting another
checker sent back is so large. QF would therefore say that X is supposed
to hit here. But no, the rollout below says that hitting is nearly a
double whopper.

The main point is that the "obvious" alternative of 5/2 puts O's
straggler behind a solid five-prime, which does a pretty good job of
containment. If we apply the usual approximation that hitting almost
always wins if O dances (and loses if O hits) then we have to judge
whether the safe play wins more than 2/3 of the time. The answer,
according to XG, is yes, on account of X's far superior structure
and the close race. Even if O hits or escapes, X retains some amount
of counterplay.

But if you want a QF play, see the variant below.

1. Rollout¹ Bar/19 5/2 eq:+0.428
Player: 72.74% (G:6.80% B:0.19%)
Opponent: 27.26% (G:0.56% B:0.00%)
Confidence: ±0.005 (+0.423..+0.433) - [100.0%]

2. Rollout¹ Bar/19 4/1* eq:+0.251 (-0.177)
Player: 64.28% (G:13.84% B:0.39%)
Opponent: 35.72% (G:5.49% B:0.05%)
Confidence: ±0.005 (+0.246..+0.256) - [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=-AaDCCC--------a----c-dccA:1:-1:1:62:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O | | O O O O | +---+
| | | O O O O | | 2 |
| | | O O O O | +---+
| | | O |
| | X | |
| |BAR| |
| | | |
| | | X |
| | | X X X X |
| | | X X X X |
| | | X X X X O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 83 O: 69 X-O: 0-0
Cube: 2, O own cube
X to play 62

1. Rollout¹ Bar/19 4/2* eq:+0.255
Player: 64.44% (G:13.91% B:0.39%)
Opponent: 35.56% (G:5.30% B:0.06%)
Confidence: ±0.004 (+0.251..+0.260) - [100.0%]

2. Rollout¹ Bar/19 3/1 eq:+0.208 (-0.047)
Player: 63.00% (G:7.76% B:0.21%)
Opponent: 37.00% (G:0.36% B:0.00%)
Confidence: ±0.004 (+0.205..+0.212) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 4-ply, cube decisions: XG Roller+
Search interval: Large

eXtreme Gammon Version: 2.19.211.pre-release

---
Tim Chow

14 Aralık 2023 Perşembe tarihinde saat 16:55:01 UTC+3 itibarıyla Timothy Chow şunları yazdı:
> XGID=-aADCCC--------a----c-dccA:1:-1:1:63:0:0:0:0:10
>
> Score is X:0 O:0. Unlimited Game
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | O | | O O O O | +---+
> | | | O O O O | | 2 |
> | | | O O O O | +---+
> | | | O |
> | | X | |
> | |BAR| |
> | | | |
> | | | X |
> | | | X X X X |
> | | | X X X X |
> | | | X X X X X O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 84 O: 70 X-O: 0-0
> Cube: 2, O own cube
> X to play 63
> Most people would not hit here, because the downside of getting another
> checker sent back is so large. QF would therefore say that X is supposed
> to hit here. But no, the rollout below says that hitting is nearly a
> double whopper.
>
> The main point is that the "obvious" alternative of 5/2 puts O's
> straggler behind a solid five-prime, which does a pretty good job of
> containment. If we apply the usual approximation that hitting almost
> always wins if O dances (and loses if O hits) then we have to judge
> whether the safe play wins more than 2/3 of the time. The answer,
> according to XG, is yes, on account of X's far superior structure
> and the close race. Even if O hits or escapes, X retains some amount
> of counterplay.
>
> But if you want a QF play, see the variant below.
>
> 1. Rollout¹ Bar/19 5/2 eq:+0.428
> Player: 72.74% (G:6.80% B:0.19%)
> Opponent: 27.26% (G:0.56% B:0.00%)
> Confidence: ±0.005 (+0.423..+0.433) - [100.0%]
>
> 2. Rollout¹ Bar/19 4/1* eq:+0.251 (-0.177)
> Player: 64.28% (G:13.84% B:0.39%)
> Opponent: 35.72% (G:5.49% B:0.05%)
> Confidence: ±0.005 (+0.246..+0.256) - [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=-AaDCCC--------a----c-dccA:1:-1:1:62:0:0:0:0:10
> Score is X:0 O:0. Unlimited Game
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | O | | O O O O | +---+
> | | | O O O O | | 2 |
> | | | O O O O | +---+
> | | | O |
> | | X | |
> | |BAR| |
> | | | |
> | | | X |
> | | | X X X X |
> | | | X X X X |
> | | | X X X X O X |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 83 O: 69 X-O: 0-0
> Cube: 2, O own cube
> X to play 62
>
> 1. Rollout¹ Bar/19 4/2* eq:+0.255
> Player: 64.44% (G:13.91% B:0.39%)
> Opponent: 35.56% (G:5.30% B:0.06%)
> Confidence: ±0.004 (+0.251..+0.260) - [100.0%]
>
> 2. Rollout¹ Bar/19 3/1 eq:+0.208 (-0.047)
> Player: 63.00% (G:7.76% B:0.21%)
> Opponent: 37.00% (G:0.36% B:0.00%)
> Confidence: ±0.004 (+0.205..+0.212) - [0.0%]
>
> ¹ 1296 Games rolled with Variance Reduction.
> Dice Seed: 271828
> Moves: 4-ply, cube decisions: XG Roller+
> Search interval: Large
>
> eXtreme Gammon Version: 2.19.211.pre-release
>
> ---
> Tim Chow
I agree with you and I would like to add that it is similar to the trap play concept described by Steve Sax on the gammonvillage website. The only difference is that the trap is set inside, not on the 7-8 points. That's why I first looked at O's inner board points. If he had three points instead of four, hitting would be a serious option.

On 12/14/2023 3:58 PM, atila...@gmail.com wrote:
> I agree with you and I would like to add that it is similar to the trap play concept described by Steve Sax on the gammonvillage website. The only difference is that the trap is set inside, not on the 7-8 points. That's why I first looked at O's inner board points. If he had three points instead of four, hitting would be a serious option.

A "trap play" usually refers to forcing the opponent off an
anchor, right? Or are you/Steve Sax using the term "trap play" in a
different sense?

---
Tim Chow

15 Aralık 2023 Cuma tarihinde saat 17:30:19 UTC+3 itibarıyla Timothy Chow şunları yazdı:
> On 12/14/2023 3:58 PM, atila...@gmail.com wrote:
> > I agree with you and I would like to add that it is similar to the trap play concept described by Steve Sax on the gammonvillage website. The only difference is that the trap is set inside, not on the 7-8 points. That's why I first looked at O's inner board points. If he had three points instead of four, hitting would be a serious option.
> A "trap play" usually refers to forcing the opponent off an
> anchor, right? Or are you/Steve Sax using the term "trap play" in a
> different sense?
>
> ---
> Tim Chow
You're right, in trap plays we force the opponent to break his anchor. In the second stage, we try to put the blots on the bar. This position is similar to the second stage. Actually, the concept of trap play is still going on.

On 12/17/2023 7:45 AM, atila...@gmail.com wrote:

> You're right, in trap plays we force the opponent to break his anchor. In the second stage, we try to put the blots on the bar. This position is similar to the second stage. Actually, the concept of trap play is still going on.

I see what you're saying. In the actual game, here's what happened.
In the position below, O was forced to run with 63.

XGID=--bDCCCB------------c-dcc-:1:-1:-1:63:0:3:0:7:10

Score is X:0 O:3 7 pt.(s) match.
+12-11-10--9--8--7-------6--5--4--3--2--1-+
| | | O O O O | +---+
| | | O O O O | | 2 |
| | | O O O O | +---+
| | | O |
| | | |
| |BAR| |
| | | |
| | | X |
| | | X X X X |
| X | | X X X X O |
| X | | X X X X O |
+13-14-15-16-17-18------19-20-21-22-23-24-+
Pip count X: 71 O: 82 X-O: 0-3/7
Cube: 2, O own cube
O to play 63

I was then all set to point on O's head, but rolled my
unluckiest roll of 65. I decided to attack anyway, although
XG says it would have played 7/1 6/1. O entered from the
bar with 41, leading to the position that I posted.

XGID=--aDCCCB---a--------c-dcc-:1:-1:1:65:0:3:0:7:10

Score is X:0 O:3 7 pt.(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O | +---+
| | | O O O O | | 2 |
| | | O O O O | +---+
| | | O |
| | | |
| |BAR| |
| | | |
| | | X |
| | | X X X X |
| 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: 71 O: 73 X-O: 0-3/7
Cube: 2, O own cube
X to play 65

1. XG Roller+ 7/1 6/1 eq:+0.405
Player: 72.54% (G:1.80% B:0.02%)
Opponent: 27.46% (G:0.11% B:0.00%)

2. XG Roller+ 7/1 7/2* eq:+0.400 (-0.005)
Player: 69.36% (G:8.07% B:0.14%)
Opponent: 30.64% (G:1.17% B:0.01%)

eXtreme Gammon Version: 2.19.211.pre-release, MET: Kazaross XG2

---
Tim Chow