Discussion:
Hit twice?
(too old to reply)
Tim Chow
2020-06-26 14:20:20 UTC
Permalink
XGID=---BabDCC---aB-b---babbb-A:0:0:1:54:0:0:0:0:10

X:Player 1 O:Player 2
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 O O |
| X O | | O O O O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| X X | | X |
| X X | | X O X |
| O X X | | X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 126 O: 129 X-O: 0-0
Cube: 1
X to play 54

---
Tim Chow
b***@gmail.com
2020-06-26 15:41:13 UTC
Permalink
Post by Tim Chow
XGID=---BabDCC---aB-b---babbb-A:0:0:1:54:0:0:0:0:10
X:Player 1 O:Player 2
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 O O |
| X O | | O O O O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| X X | | X |
| X X | | X O X |
| O X X | | X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 126 O: 129 X-O: 0-0
Cube: 1
X to play 54
---
Tim Chow
No way we hit two with cube access. (and being so outboarded and blah blah blah)

Stick
Peter
2020-06-26 15:57:14 UTC
Permalink
Post by Tim Chow
XGID=---BabDCC---aB-b---babbb-A:0:0:1:54:0:0:0:0:10
X:Player 1 O:Player 2
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 O O |
| X O | | O O O O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| X X | | X |
| X X | | X O X |
| O X X | | X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 126 O: 129 X-O: 0-0
Cube: 1
X to play 54
---
Tim Chow
No 20*/16
Paul Epstein
2020-06-26 21:52:00 UTC
Permalink
Post by Tim Chow
XGID=---BabDCC---aB-b---babbb-A:0:0:1:54:0:0:0:0:10
X:Player 1 O:Player 2
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 O O |
| X O | | O O O O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| X X | | X |
| X X | | X O X |
| O X X | | X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 126 O: 129 X-O: 0-0
Cube: 1
X to play 54
---
Tim Chow
I find it hard to resist hit-twice plays so I would (probably wrongly) hit
twice OTB. It's extremely unlikely that Stick and Peter are both
wrong so I'll just wait for my punishment.
Hitting twice gives the opponent a 1/3 probability of rehitting.
Peter's ingenious play of bar/16 gives the opponent a probability of
rehitting of only 11/36 -- a massive 2.78% gain in safety.
Are we meant to play something so passive as 7/3?

Paul
Tim Chow
2020-06-28 19:01:03 UTC
Permalink
XGID=---BabDCC---aB-b---babbb-A:0:0:1:54:0:0:0:0:10

X:Player 1 O:Player 2
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 O O |
| X O | | O O O O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| X X | | X |
| X X | | X O X |
| O X X | | X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 126 O: 129 X-O: 0-0
Cube: 1
X to play 54

Magriel's criteria suggest a safe play. Stick mentions cube access, which
also suggests safety, although XG doesn't hit twice even when the cube is
turned. For giggles, I've provided a variant.

1. Rollout¹ Bar/20* 20/16 eq:+0.530
Player: 64.05% (G:12.26% B:0.36%)
Opponent: 35.95% (G:8.51% B:0.25%)
Confidence: ±0.012 (+0.518..+0.541) - [100.0%]

2. Rollout¹ Bar/20* 8/4* eq:+0.442 (-0.088)
Player: 60.75% (G:21.62% B:0.75%)
Opponent: 39.25% (G:12.97% B:0.42%)
Confidence: ±0.012 (+0.429..+0.454) - [0.0%]

3. Rollout¹ Bar/20* 7/3 eq:+0.392 (-0.138)
Player: 59.51% (G:15.01% B:0.56%)
Opponent: 40.49% (G:10.84% B:0.28%)
Confidence: ±0.014 (+0.378..+0.406) - [0.0%]

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

eXtreme Gammon Version: 2.19.207.pre-release

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

XGID=---BabDCC---aB-b---babca-A:0:0:1:54:0:0:0:0:10

X:Player 1 O:Player 2
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 O O |
| X O | | O O O |
| | | O |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| X X | | X |
| X X | | X O X |
| O X X | | X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 126 O: 130 X-O: 0-0
Cube: 1
X to play 54

1. Rollout¹ Bar/20* 8/4* eq:+0.765
Player: 68.38% (G:28.57% B:1.23%)
Opponent: 31.62% (G:8.23% B:0.30%)
Confidence: ±0.011 (+0.754..+0.776) - [86.2%]

2. Rollout¹ Bar/20* 20/16 eq:+0.757 (-0.008)
Player: 69.23% (G:16.25% B:0.62%)
Opponent: 30.77% (G:6.16% B:0.17%)
Confidence: ±0.011 (+0.746..+0.767) - [13.8%]

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

eXtreme Gammon Version: 2.19.207.pre-release

---
Tim Chow
Paul Epstein
2020-06-28 22:51:46 UTC
Permalink
Post by Tim Chow
XGID=---BabDCC---aB-b---babbb-A:0:0:1:54:0:0:0:0:10
X:Player 1 O:Player 2
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 O O |
| X O | | O O O O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| X X | | X |
| X X | | X O X |
| O X X | | X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 126 O: 129 X-O: 0-0
Cube: 1
X to play 54
Magriel's criteria suggest a safe play. Stick mentions cube access, which
also suggests safety, although XG doesn't hit twice even when the cube is
turned. For giggles, I've provided a variant.
But (as I said), bar/16 is only 2.78% safer than hitting twice.
You need to actually count shots (as I did).

Paul
Tim Chow
2020-06-30 00:25:59 UTC
Permalink
Post by Paul Epstein
But (as I said), bar/16 is only 2.78% safer than hitting twice.
You need to actually count shots (as I did).
I believe that leaving two blots makes a significant difference.
It's not just the number of shots.

---
Tim Chow

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