Blitz versus prime checker play

[Timothy Chow]

XGID=cABBBABaa---aA---bbcb-B-B-:1:1:1:32:0:0:0:0:10

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 X |
| O O | | O O X X |
| | | O |
| | | |
| | | |
| |BAR| |
| | O | |
| | O | |
| | O | | +---+
| | | X X X X | | 2 |
| O O O | | X X X X X X | +---+
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 141 O: 181 X-O: 0-0
Cube: 2, X own cube
X to play 32

---
Tim Chow

[Timothy Chow]

In a blitz, one should generally focus on attack first and defense
second. But here, X has four checkers behind O's five-prime, and
urgently needs to escape before collapsing. So 24/21 is a must,
and then the question is whether leaving the 5pt slotted (hoping to
make it) is worth the risk of getting it sent back. Again, under
"normal" blitz conditions, the gain of making the 5pt might be
worth the risk of leaving a direct shot, but here, XG says it's a
whopper with cheese to play 24/21 13/11.

If X didn't have so many checkers boxed in behind O's prime then
the decision would be a lot more complicated (see variant).

1. Rollout¹ 24/21 5/3 eq:+0.948
Player: 63.51% (G:51.16% B:12.26%)
Opponent: 36.49% (G:10.09% B:0.49%)
Confidence: ±0.020 (+0.929..+0.968) - [100.0%]

2. Rollout¹ 24/21 13/11 eq:+0.786 (-0.162)
Player: 59.86% (G:46.29% B:12.73%)
Opponent: 40.14% (G:12.41% B:0.59%)
Confidence: ±0.020 (+0.765..+0.806) - [0.0%]

3. Rollout¹ 13/8* eq:+0.738 (-0.210)
Player: 57.97% (G:44.05% B:10.60%)
Opponent: 42.03% (G:12.74% B:0.72%)
Confidence: ±0.024 (+0.714..+0.763) - [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=cABBBABaa---aA--AbbcbB--A-:1:1:1:32:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+

| X X O O | | O O X X |

| O O | | O O X |

| | | O |
| | | |
| | | |
| |BAR| |
| | O | |
| | O | |
| | O | | +---+
| | | X X X X | | 2 |
| O O O | | X X X X X X | +---+
+12-11-10--9--8--7-------6--5--4--3--2--1-+

Pip count X: 131 O: 181 X-O: 0-0

Cube: 2, X own cube
X to play 32

1. Rollout¹ 24/21 5/3 eq:+1.360
Player: 74.93% (G:63.06% B:18.66%)
Opponent: 25.07% (G:5.49% B:0.23%)
Confidence: ±0.014 (+1.346..+1.374) - [99.9%]

2. Rollout¹ 16/13 5/3 eq:+1.327 (-0.033)
Player: 74.26% (G:62.29% B:17.97%)
Opponent: 25.74% (G:5.65% B:0.28%)
Confidence: ±0.014 (+1.313..+1.342) - [0.1%]

3. Rollout¹ 13/8* eq:+1.326 (-0.034)
Player: 73.48% (G:60.05% B:19.21%)
Opponent: 26.52% (G:5.96% B:0.28%)
Confidence: ±0.014 (+1.312..+1.340) - [0.0%]

4. Rollout¹ 24/22 5/2 eq:+1.315 (-0.045)
Player: 73.86% (G:62.22% B:17.32%)
Opponent: 26.14% (G:6.29% B:0.30%)
Confidence: ±0.015 (+1.300..+1.331) - [0.0%]

5. Rollout¹ 24/21 13/11 eq:+1.252 (-0.108)
Player: 70.79% (G:57.25% B:18.76%)
Opponent: 29.21% (G:7.39% B:0.33%)
Confidence: ±0.012 (+1.240..+1.264) - [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


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Tim Chow