Gaining Time (Part 2)

 

For me making the right play in a position like 2-18 is hard because leaving the blot just seems “wrong.” Understanding the big picture and to what you are accomplishing with a play goes a long way in helping to overcome that. The position Trice gives is:

Pip counts: Blue 139, Red 158
Position ID: 4LuFAyCMx+EBUA Match ID: cIkVAAAAAAAA

I am not sure what I would have done in this position before reading Trice. You are going to have to create another blot here no matter what, so I would have probably gone with bar/22 13/8 or bar/20 13/10 trying to leave as few direct shots as I could. 

I explored some variations on this position to try and determine when to hit or not hit. One of the problems with doing this from this position is that it is easy to end up with positions where the reason for hitting or not hitting is something other than gaining time. However I found the differences in the following two positions interesting.

Pip counts: Blue 119, Red 155
Position ID: bLuBAyCM5+ABUA Match ID: cInmAGAAMAAA

• Red moves bar/24 6/1*

#		Ply	Move	Equity
	1	R	bar/24 13/8	-0.619
			0.191 0.029 0.002 – 0.809 0.369 0.102 -0.619 -0.619 0.002 0.002 0.001 – 0.002 0.007 0.005 0.005 0.005
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 871233900 and quasi-random dice
			Play: 0-ply cubeful [expert]
			Cube: 2-ply cubeful prune [world class]
•	2	R	bar/24 6/1*	-0.637 ( -0.018)
			0.182 0.025 0.001 – 0.818 0.445 0.144 -0.637 -0.637 0.003 0.002 0.000 – 0.003 0.008 0.007 0.005 0.005
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 871233900 and quasi-random dice
			Play: 0-ply cubeful [expert]
			Cube: 2-ply cubeful prune [world class]
	3	R	bar/24 8/3	-0.643 ( -0.024)
			0.179 0.027 0.002 – 0.821 0.390 0.102 -0.643 -0.643 0.003 0.003 0.001 – 0.003 0.010 0.008 0.006 0.006
			Full cubeful rollout with var.redn.
			648 games, Mersenne Twister dice gen. with seed 871233900 and quasi-random dice
			Play: 0-ply cubeful [expert]
			Cube: 2-ply cubeful prune [world class]

The above was my attempt to answer the question about whether or not the hit was still correct if blue had a more closed board. In this position hitting loses to 13/8, but only by a small amount. But the issue does not seem to be just the closed board but the threat blue has to make another point.  If you move 3 checkers back so that blue is not as likely to make another home board point in the next couple of rolls then the hit comes out on top.  In both cases however the equities between the two moves is very close, a longer or world class rollout could well give different results. So hitting in either case would not be a particular bad move.

Pip counts: Blue 131, Red 155
Position ID: bBuaAyCM5+ABUA Match ID: cInmAGAAMAAA

#		Ply	Move	Equity
•	1	R	bar/24 6/1*	-0.538
			0.231 0.054 0.005 – 0.769 0.413 0.145 -0.538 -0.538 0.003 0.003 0.001 – 0.003 0.007 0.007 0.005 0.005
	2	R	bar/24 13/8	-0.540 ( -0.002)
			0.230 0.058 0.005 – 0.770 0.379 0.086 -0.540 -0.540 0.002 0.003 0.001 – 0.002 0.007 0.005 0.005 0.005
	3	R	bar/24 8/3	-0.576 ( -0.038)
			0.212 0.051 0.003 – 0.788 0.398 0.103 -0.576 -0.576 0.003 0.003 0.001 – 0.003 0.007 0.006 0.006 0.006

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