         
 
          
 | | White is Player 2
score: 0
pip: 133 | Unlimited Game
Jacoby Beaver | pip: 121
score: 0
Blue is Player 1 |
|
| XGID=-B-BaaC-CA-AbB--abbc-b--aA:0:0:1:11:0:0:3:0:10 |
Feature Position #1
32S-11P-63R-52S-52D-52S-53T-42o-62R-62B-21H-11B-55A-53H-11 |
In the position above (reachable by the perfectly played sequence in red), it is clearly right for Blue to hit with three aces, as shown below. He is left with one ace to play.
 
  
| | White is Player 2
score: 0
pip: 166 | Unlimited Game
Jacoby Beaver | pip: 118
score: 0
Blue is Player 1 |
|
| XGID=cB-BA-B-CA-AbB--abbc-b--A-:0:0:1:00:0:0:3:0:10 |
| Blue to play ONE ace |
When the Jacoby rule is in effect, Blue should lift his final ace (to do otherwise is a whopper). He will have nothing better than to cash after White enters with one checker, and it is definitely not worth the risk of being hit one-third of the time by a 4. Blue experiences (slight) lift-regret only when White rolls 55, or 52 (yielding a close take).
Conversely, if the cube is no longer in the center, or if one has (irregularly) agreed to not use the Jacoby in a money game, or more commonly if one is playing a MATCH at "normal" scores (both sides are enough points away from winning the match that the possibility of a cube-turn does not materially affect the gammon price¡Xreferred to as Unlimited No-Jacoby), the Jacoby rule is NOT in effect, and Blue can therefore win a gammon without turning the cube. In that case, Blue should leave his 4pt slotted and spread his builders with 8/7.
The contrasting Jacoby and non-Jacoby rollouts are shown below. (They can be viewed side-by-side if you widen your window enough.) Following that, our second feature position will appear.
| | White is Player 2
score: 0
pip: 133 | Unlimited Game
Jacoby Beaver | pip: 121
score: 0
Blue is Player 1 |
|
| XGID=-B-BaaC-CA-AbB--abbc-b--aA:0:0:1:11:0:0:3:0:10 |
| With Jacoby |
| 1. | Rollout1 | Bar/24* 6/5* 5/4* 4/3 | eq: +0.889 |
| Player:
Opponent: | 67.42% (G:49.37% B:3.48%)
32.58% (G:7.01% B:0.45%) | Conf.: ¡Ó 0.003 (+0.886...+0.893) - [100.0%]
Duration: 20 minutes 10 seconds |
|
| 2. | Rollout1 | Bar/24* 8/7 6/5* 5/4* | eq: +0.752 (-0.137) |
| Player:
Opponent: | 69.34% (G:52.24% B:4.69%)
30.66% (G:7.81% B:0.66%) | Conf.: ¡Ó 0.006 (+0.745...+0.758) - [0.0%]
Duration: 47 minutes 26 seconds |
|
| |
1 5184 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
|
| | White is Player 2
score: 0
pip: 133 | | Unlimited Game | pip: 121
score: 0
Blue is Player 1 |
|
| XGID=-B-BaaC-CA-AbB--abbc-b--aA:0:0:1:11:0:0:0:0:10 |
| With NO Jacoby |
| 1. | Rollout1 | Bar/24* 8/7 6/5* 5/4* | eq: +0.956 |
| Player:
Opponent: | 69.79% (G:53.26% B:5.85%)
30.21% (G:7.85% B:0.66%) | Conf.: ¡Ó 0.008 (+0.948...+0.964) - [100.0%]
Duration: 3 hours 10 minutes |
|
| 2. | Rollout1 | Bar/24* 6/5* 5/4* 4/3 | eq: +0.939 (-0.018) |
| Player:
Opponent: | 68.08% (G:50.76% B:4.32%)
31.92% (G:7.13% B:0.45%) | Conf.: ¡Ó 0.005 (+0.934...+0.944) - [0.0%]
Duration: 1 hour 49 minutes |
|
| |
1 5184 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
|
Below is our second feature position. (It is the same as the position in this post, except that White's 9pt checker has been moved to the 7pt.) Double 1s is our roll of the day, and again Blue is to play it.
  
| | White is Player 2
score: 0
pip: 117 | Unlimited Game
Jacoby Beaver | pip: 150
score: 0
Blue is Player 1 |
|
| XGID=--aaBBBBA---BAA--adbbbbAA-:0:0:1:11:0:0:3:0:10 |
| Feature Position #2 |
In the position above (for money or money-like scores), Blue should anchor and switch to the 3pt with three aces, as shown below. He is left with one ace to play.
| | White is Player 2
score: 0
pip: 120 | Unlimited Game
Jacoby Beaver | pip: 147
score: 0
Blue is Player 1 |
|
| XGID=a-aB-BBBA---BAA--adbbbbB--:0:0:1:00:0:0:3:0:10 |
| Blue to play ONE ace |
If the Jacoby rule is in effect, Blue can afford to (and should) leave five blots with 12/11 as his final ace. The key is that even with Blue's loose play, White's position is currently not strong enough to justify turning the cube. That is, with Jacoby in effect, Blue should risk 12/11 in order to strive for the strongest follow-up position. If Blue gets hit, his loss is limited to 1 point, with White often missing her market by a mile (and even being "too good" if only Jacoby were not in effect).
On the other hand, if the cube is no longer in the center, or if one is playing a MATCH (at normal scores), the Jacoby rule is NOT in effect, and in that case one should lift the fourth ace with 8/7 (also best at gammon save). Granted, White otherwise hits with only 7 numbers, but with enormous impact.
The contrasting Jacoby and non-Jacoby rollouts appear below.
Note that in Feature Position #1, Blue should play conservatively because of the Jacoby (he guards against turnarounds while reducing the amount by which he will likely lose his market), whereas in Feature Position #2, Blue should play boldly because of Jacoby (he creates opportunities for White to lose her market)!
Positions in which the Jacoby rule swings the best play do not occur often, but they do occur. I hope these examples help.
Nack
| | White is Player 2
score: 0
pip: 117 | Unlimited Game
Jacoby Beaver | pip: 150
score: 0
Blue is Player 1 |
|
| XGID=--aaBBBBA---BAA--adbbbbAA-:0:0:1:11:0:0:3:0:10 |
| With Jacoby |
| 1. | Rollout1 | 24/23 12/11 4/3*(2) | eq: +0.250 |
| Player:
Opponent: | 56.85% (G:13.50% B:0.60%)
43.15% (G:17.91% B:1.68%) | Conf.: ¡Ó 0.007 (+0.243...+0.257) - [100.0%]
Duration: 1 hour 09 minutes |
|
| 2. | Rollout1 | 24/23 8/7 4/3*(2) | eq: +0.215 (-0.035) |
| Player:
Opponent: | 56.01% (G:14.31% B:0.64%)
43.99% (G:15.43% B:1.02%) | Conf.: ¡Ó 0.007 (+0.208...+0.222) - [0.0%]
Duration: 1 hour 13 minutes |
|
| |
1 5184 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
|
| | White is Player 2
score: 0
pip: 117 | | Unlimited Game | pip: 150
score: 0
Blue is Player 1 |
|
| XGID=--aaBBBBA---BAA--adbbbbAA-:0:0:1:11:0:0:0:0:10 |
| With NO Jacoby |
| 1. | Rollout1 | 24/23 8/7 4/3*(2) | eq: +0.223 |
| Player:
Opponent: | 56.04% (G:14.73% B:0.66%)
43.96% (G:15.17% B:0.97%) | Conf.: ¡Ó 0.007 (+0.216...+0.229) - [97.5%]
Duration: 1 hour 13 minutes |
|
| 2. | Rollout1 | 24/23 12/11 4/3*(2) | eq: +0.212 (-0.010) |
| Player:
Opponent: | 56.48% (G:13.87% B:0.62%)
43.52% (G:18.35% B:2.01%) | Conf.: ¡Ó 0.007 (+0.205...+0.220) - [2.5%]
Duration: 1 hour 15 minutes |
|
| |
1 5184 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
|