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Problem #7 solution
Match to 11
Blue 1, White 0
Blue to play 33 Candidate plays:
24/18 21/18(2) 24/18 21/18 13/10 24/18 21/18 6/3 24/18 5/2(2)* 21/15 21/18(2) 21/15 5/2(2)* 21/18(2) 5/2(2)* 21/18 13/10 5/2(2)* 13/7(2)
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RK:
One obvious play is to bring down both checkers from the midpoint to make a five-prime. A five-prime is always very nice to have, particularly when there's at least one checker behind it. The opponent is an underdog to escape on any given roll, and it should be fairly easy for Blue to move his spare back checkers (except with an immediate 44 or 22).However, in this position there are a few problems with this play:
- Giving up the midpoint is a drawback. If White rolls a 6, Blue has no coverage of the escaping checker. It'll be much easier for White to bring home that checker, and the two on the midpoint, without Blue's midpoint in the way.
- If White doesn't roll a 6, she has some numbers to point on Blue's blot on the ace point.
- Blue doesn't have enough checkers in position to make a full prime yet, so there will always be some chance for White's checker to escape.
A good option is to make the defensive bar point with three of the 3s. Blue still has a four-prime, which isn't as good as a five-prime, but in return, Blue gets to beef up his defense and take greater control of the outfield. And there's no chance of being attacked. If White manages to escape, Blue still has a solid defensive position from which to play.
After making the bar point, what should Blue do with the fourth 3? Playing 6/3 seems obvious, but take a look at 13/10. Exposing two blots voluntarily isn't as strange as it might appear:
By the way, another idea that might come to mind is switching points with 5/2*(2). It has the advantage of slowing White down and ensuring that she can't escape on this roll. The disadvantage is the loss of the 5 point, which weakens Blue's prime considerably. In some positions, this type of play can be correct, but here, since Blue is so far behind and is short on ammunition, it's unrealistic to think that he can stop White by attacking now. Keeping four points in a row serves Blue better in the long run.
- White is way ahead in the race and her main goal is to escape her back checker. She has little interest in breaking her midpoint to hit with a 1 and subjecting herself to return shots. So the blot left on the midpoint is relatively safe.
- Blue has more coverage of the outfield in case the checker escapes partially with a 52 (although this is somewhat offset by the chance of getting hit with other numbers).
- If the checker doesn't escape, Blue has more numbers to attack it (4s, 8s and 65 instead of just 1s and 65) or to make the bar point (63 and 33 instead of 66 and 33).
- On the next roll, Blue is likely to have to break the midpoint anyway (or one of his anchors) so by breaking it now, he has more flexibility in playing the next roll.
Pip counts: Blue 155 White 110 Blue White Candidate Plays Equity Win G/BG BG Win G/BG BG 24/18 21/18 13/10 -0.051 48.7% 11.3% 0.3% 51.3% 13.9% 0.3% 24/18 12/18 6/3 -0.077 47.2% 10.5% 0.3% 52.8% 12.6% 0.3% 24/15 21/18 -0.080 48.4% 11.9% 0.4% 51.6% 16.8% 0.4% 24/15 6/3 -0.103 46.2% 11.1% 0.4% 53.8% 13.7% 0.4% 13/7(2) -0.105 46.6% 11.0% 0.4% 53.4% 14.8% 0.4% 21/15 5/2(2)* -0.112 45.8% 12.4% 0.3% 54.2% 15.1% 0.5% 24/18 5/2(2)* -0.137 44.5% 10.5% 0.2% 55.5% 13.0% 0.4% 24/18 21/18(2) -0.159 44.7% 9.5% 0.2% 55.3% 14.9% 0.2% 21/18 13/10 5/2(2)* -0.159 45.5% 12.5% 0.4% 54.5% 18.9% 0.9% 21/18(2) 5/2(2)* -0.170 44.7% 11.4% 0.3% 55.3% 17.6% 0.5% 21/15 21/18(2) -0.184 46.1% 12.6% 0.4% 53.9% 23.1% 0.6%
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