Question:
Red to play 4-4
Option 1: 18/6-13/9
votes: 2
Option 2: 18/14(2)-13/9(2)
votes: 1
Option 3: 18/10(2)
votes: 6
Option 4: 18/2
votes: 0
Option 5: 13/5(2)
votes: 0
Position information:
Score: Red 2-5 White
Pip-count: Red 117-119
Match: 7-pointer
(http://www.freewebs.com/persianlord/position21.png)
Spoiler
Here winning the game is almost guaranteed for red, as he has a very strong home plus better position and the deteriorated white's board. Thus, red must focus his plans to win a gammon and 4 points. This is achieved when red hits as many white's blots as he can and prevents white from bringning the rest of his men home. In order to do this and taking into account the crushed white's board, red must increase contacts as high as he can, so that he may be able to take advantage of his strong board. Thus, the natural looking move of 18/10(2) is the worst thing red can think of as it allows white to bring the rest of his desperate men home with ease and decreases the contacts. The right play that increases the gammon win probability most is 18/2!
1. Cubeful 2-ply 18/2 Eq.: +1.111 MWC: 41.90%
0.878 0.233 0.008 - 0.122 0.039 0.001
2. Cubeful 2-ply 18/6 13/9 Eq.: +1.079 ( -0.032) MWC: 41.27%
0.874 0.218 0.008 - 0.126 0.025 0.000
3. Cubeful 2-ply 18/10 13/9(2) Eq.: +1.046 ( -0.065) MWC: 40.61%
0.869 0.202 0.007 - 0.131 0.023 0.000
4. Cubeful 2-ply 18/10 13/5 Eq.: +1.041 ( -0.070) MWC: 40.52%
0.857 0.214 0.008 - 0.143 0.032 0.001
5. Cubeful 2-ply 18/10 18/14 13/9 Eq.: +1.036 ( -0.075) MWC: 40.41%
0.894 0.164 0.005 - 0.106 0.023 0.001
The passive play of 18/10(2) is 9th :
9. Cubeful 2-ply 18/10(2) Eq.: +1.022 ( -0.089) MWC: 40.13%
0.894 0.156 0.004 - 0.106 0.017 0.000
As can be seen, by playing 18/10(2) red's GWC is 89.4%, compared to 87.8% for 18/2 but as I said, here red must wage an all-out war to win a gammon. The probability of a gammon win with 18/10(2) is just 15.6%, compared to the whopping 23.3% for 18/2., hence the GNUBG's advice.