XGID=-BCa--EBBa--a-b--bab-c--bA:0:0:1:42:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O O | | O O O |
| O O | | O O O |
| | | O |
| | | |
| | X | |
| |BAR| |
| | | X |
| | | X |
| | | X X |
| X X | | X X X |
| O O X X | | X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 93 O: 122 X-O: 0-0
Cube: 1
X to play 42

---
Tim Chow

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

On Sunday, March 26, 2023 at 9:39:09 AM UTC-4, Timothy Chow wrote:

XGID=-BCa--EBBa--a-b--bab-c--bA:0:0:1:42:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O O | | O O O |
| O O | | O O O |
| | | O |
| | | |
| | X | |
| |BAR| |
| | | X |
| | | X |
| | | X X |
| X X | | X X X |
| O O X X | | X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 93 O: 122 X-O: 0-0
Cube: 1
X to play 42

---
Tim Chow

It doesn't seem like an awesome tempo play to me. It looks like it's setting O up to play offence of two fronts now instead of one, and X, relying on a racing lead, should hope to fight only one battle.
Bar/23 6/2
Bob

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

XGID=-BCa--EBBa--a-b--bab-c--bA:0:0:1:42:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O O | | O O O |
| O O | | O O O |
| | | O |
| | | |
| | X | |
| |BAR| |
| | | X |
| | | X |
| | | X X |
| X X | | X X X |
| O O X X | | X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 93 O: 122 X-O: 0-0
Cube: 1
X to play 42

XG's answer to the subject line is yes. There will be a big swing if
O fails to make her bar and X manages to hit that blot. If we lift
O's blot on her bar point to her 6pt, then XG plays safe (see variant).

1. Rollout¹ Bar/23 7/3* eq:-0.053
Player: 47.38% (G:21.31% B:0.80%)
Opponent: 52.62% (G:14.50% B:0.69%)
Confidence: ±0.009 (-0.062..-0.043) - [100.0%]

2. Rollout¹ Bar/23 6/2 eq:-0.159 (-0.107)
Player: 44.80% (G:12.44% B:0.20%)
Opponent: 55.20% (G:9.03% B:0.28%)
Confidence: ±0.012 (-0.171..-0.147) - [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=-BCa--EBBa--a-b--b-c-c--bA:0:0:1:42:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O | | O O O |
| O O | | O O O |
| | | O O |
| | | |
| | X | |
| |BAR| |
| | | X |
| | | X |
| | | X X |
| X X | | X X X |
| O O X X | | X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 93 O: 121 X-O: 0-0
Cube: 1
X to play 42

1. Rollout¹ Bar/23 6/2 eq:-0.139
Player: 46.03% (G:10.88% B:0.16%)
Opponent: 53.97% (G:8.19% B:0.23%)
Confidence: ±0.009 (-0.148..-0.129) - [92.5%]

2. Rollout¹ Bar/23 7/3* eq:-0.149 (-0.011)
Player: 45.41% (G:14.14% B:0.30%)
Opponent: 54.59% (G:12.80% B:0.61%)
Confidence: ±0.011 (-0.160..-0.138) - [7.5%]

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

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

XGID=-Fa-CEa--a----aa---b-bbbbA:1:-1:1:52:0:0:0:0:10

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 O O O | | 2 |
| | | | +---+
| | | |
| | X | |
| |BAR| |
| | | X 6 |
| | | X X |
| | | X X X |
| | | X X X |
| O | | O X X O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 68 O: 111 X-O: 0-0
Cube: 2, O own cube
X to play 52

---
Tim Chow

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

XGID=-Fa-CEa--a----aa---b-bbbbA:1:-1:1:52:0:0:0:0:10

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 O O O | | 2 |
| | | | +---+
| | | |
| | X | |
| |BAR| |
| | | X 6 |
| | | X X |
| | | X X X |
| | | X X X |
| O | | O X X O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 68 O: 111 X-O: 0-0
Cube: 2, O own cube
X to play 52

When you're trying to scramble a single checker home, your tendency
may be to avoid exposing another blot at all costs, because after all,
if the second blot gets hit then you're really going to be in trouble.
On the other hand, hitting typically reduces the number of ways your
opponent can hit you, and typically has a better upside---your opponent
may dance or otherwise roll poorly, giving you a chance to turn the
tables.

Here, bar/18 gives the opponent 25 hitting rolls, while bar/20 4/2*
gives the opponent 19 hitting rolls, plus 9 dancing rolls which
suddenly make X a big favorite, with serious gammon chances. For
comparison, see the variant, in which XG prefers the pedestrian bar/18.

1. Rollout¹ Bar/20 4/2* eq:-0.356
Player: 39.27% (G:16.39% B:0.17%)
Opponent: 60.73% (G:14.11% B:0.41%)
Confidence: ±0.006 (-0.362..-0.350) - [100.0%]

2. Rollout¹ Bar/18 eq:-0.490 (-0.134)
Player: 37.00% (G:6.75% B:0.07%)
Opponent: 63.00% (G:3.31% B:0.06%)
Confidence: ±0.008 (-0.498..-0.481) - [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=-Fa-CEa--a----a----c-bbbbA:1:-1:1:52:0:0:0:0:10

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 O O | | 2 |
| | | O | +---+
| | | |
| | X | |
| |BAR| |
| | | X 6 |
| | | X X |
| | | X X X |
| | | X X X |
| O | | O X X O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 68 O: 107 X-O: 0-0
Cube: 2, O own cube
X to play 52

1. Rollout¹ Bar/18 eq:-0.365
Player: 42.25% (G:5.05% B:0.05%)
Opponent: 57.75% (G:3.11% B:0.07%)
Confidence: ±0.005 (-0.370..-0.360) - [100.0%]

2. Rollout¹ Bar/20 4/2* eq:-0.417 (-0.052)
Player: 38.08% (G:11.83% B:0.13%)
Opponent: 61.92% (G:14.03% B:0.43%)
Confidence: ±0.004 (-0.421..-0.413) - [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

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

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

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

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

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

On 12/14/2023 3:58 PM, [email protected] 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

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

On 12/17/2023 7:45 AM, [email protected] 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

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