Bringing It Home (Part 2)

 

The following position is not from Trice but fits will with the subject of the this chapter and is a point well worth exploring.

Pip counts: Blue 142, Red 76
Position ID: 2O4GABzZ3TYAAA Match ID: cInoAGAAMAAA

The “obvious” play with this is 8/7 8/6, clearing form the back of the prime and avoiding gaps. The problem with this play is that it creates an issue with clearing reds bar point. The big problem are 5’s, which would have to be played form the 6 point leaving a gap in the home board. If the 6 point is cleared before the bar point 5’s than have the potential to force red to leave a blot on the bar point.

While 7/5 7/6 leaves a gap on the bar point it allows much more flexibility in this position.  This problem is an example of looking for problem numbers in the bear in and playing to minimize their impact. It comes from an article by Kit Woolsey that discusses this topic with several other examples. The article may be found at http://www.bkgm.com/articles/GOL/Nov02/safe.htm.

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Bringing It Home (Part 1)

Whenever I am getting to the end of the game with my opponent still having checkers back I am never really sure that I am playing things right. That is where the chapter on Bringing It Home comes in. One of my issues was to simply rush into my home board and then try to bear off from there. Trice’s examples of playing to allow for the big doubles has already helped me in these positions and I am sure that as I work through more examples of the end game I will get better at seeing the potential problems in these kinds of positions and hopefully avoiding them much more often.

The other situations are those like Trice illustrates in position 2-16. The  loose hit in positions like this feels really risky, so it takes some study to realize that hitting is often the right play in these positions.

The position below presents a similar situation as 2-16, but in analyzing it I came up with a couple of interesting things.

Pip counts: Blue 134, Red 73
Position ID: bDuJAUiz3TkAAA Match ID: cAnxAGAAMAAA

Unlike 2-16 at DMP in this position the correct play is not to hit, but to make a safe play 8/4 5/3 coming out on top (although 8/2*  only gives up a little over 0.01 equity so it is hardly a terrible choice).

As you would expect at 2-away 1-away Crawford 8/2* becomes the clear choice because it gives more gammon chances giving red a better chance to win the match without another game.

What I found surprising was the results at 3-away 1-away. I expected the answer to be the same as DMP because a gammon does not really gain anything for red since if they have to win two games anyway. One though I had on this is that the possibility of a backgammon is what drives the play in this situation. However, even at 0-0 in a 7 point match the hit comes out ahead. I found this even more surprising.  Looking at the equities in the rollouts this position demonstrates the complexity of match play and the differences that can occur depending upon the match score. Getting into the details of this is getting quite a bit ahead of ourselves, but it is something to keep in mind.

Without getting to wrapped up in the details my take away from this is that I should consider hitting the blot in these situations a lot more than I would have in the past.  Even if it is wrong as a DMP it is not wrong by that much. Of course, I am sure that I now run the risk of over generalizing this and hitting when I should not. That will take more learning.

Rollouts

DMP

#		Ply	Move	Equity
	1	R	8/4 5/3	+0.747
			0.874 0.682 0.046 – 0.126 0.007 0.000 +0.747 +0.747 0.002 0.012 0.005 – 0.002 0.002 0.000 0.004 0.004
	2	R	8/6 8/4	+0.746 ( -0.001)
			0.873 0.706 0.044 – 0.127 0.004 0.001 +0.746 +0.746 0.002 0.011 0.005 – 0.002 0.001 0.000 0.004 0.004
	3	R	8/4 6/4	+0.739 ( -0.008)
			0.870 0.668 0.047 – 0.130 0.004 0.000 +0.739 +0.739 0.002 0.011 0.005 – 0.002 0.001 0.000 0.004 0.004
•	4	R	8/2*	+0.733 ( -0.014)
			0.866 0.757 0.029 – 0.134 0.023 0.001 +0.733 +0.733 0.002 0.009 0.004 – 0.002 0.003 0.000 0.004 0.004
	5	R	8/6 5/1	+0.661 ( -0.087)
			0.830 0.623 0.042 – 0.170 0.010 0.001 +0.661 +0.661 0.002 0.012 0.005 – 0.002 0.002 0.000 0.005 0.005

2-away, 1-away Crawford

#		Ply	Move	Equity
•	1	R	8/2*	+2.161
			0.867 0.713 0.048 – 0.133 0.017 0.000 +2.161 +2.161 0.002 0.003 0.005 – 0.002 0.003 0.001 0.009 0.009
	2	R	8/6 8/4	+1.880 ( -0.281)
			0.867 0.573 0.037 – 0.133 0.007 0.000 +1.880 +1.880 0.002 0.003 0.004 – 0.002 0.003 0.000 0.008 0.008
	3	R	8/4 5/3	+1.851 ( -0.310)
			0.874 0.552 0.027 – 0.126 0.010 0.000 +1.851 +1.851 0.002 0.004 0.003 – 0.002 0.002 0.000 0.008 0.008
	4	R	8/4 6/4	+1.808 ( -0.353)
			0.873 0.531 0.033 – 0.127 0.011 0.000 +1.808 +1.808 0.002 0.004 0.004 – 0.002 0.002 0.000 0.008 0.008
	5	R	8/6 5/1	+1.664 ( -0.498)
			0.837 0.495 0.023 – 0.163 0.017 0.000 +1.664 +1.664 0.002 0.004 0.003 – 0.002 0.002 0.000 0.009 0.009

3-away 1-away Crawford

#		Ply	Move	Equity
•	1	R	8/2*	+0.809
			0.861 0.705 0.021 – 0.139 0.023 0.001 +0.809 +0.809 0.002 0.003 0.002 – 0.002 0.003 0.000 0.006 0.006
	2	R	8/4 5/3	+0.798 ( -0.011)
			0.873 0.578 0.008 – 0.127 0.006 0.000 +0.798 +0.798 0.002 0.004 0.001 – 0.002 0.003 0.000 0.004 0.004
	3	R	8/6 8/4	+0.794 ( -0.015)
			0.869 0.601 0.009 – 0.131 0.006 0.001 +0.794 +0.794 0.002 0.004 0.001 – 0.002 0.001 0.000 0.004 0.004
	4	R	8/4 6/4	+0.788 ( -0.021)
			0.869 0.560 0.007 – 0.131 0.007 0.000 +0.788 +0.788 0.002 0.004 0.001 – 0.002 0.001 0.000 0.004 0.004
	5	R	8/6 5/1	+0.702 ( -0.107)
			0.830 0.518 0.005 – 0.170 0.011 0.001 +0.702 +0.702 0.002 0.004 0.001 – 0.002 0.002 0.000 0.005 0.005

0-0 to 7

#		Ply	Move	Equity
•	1	R	8/2*	+1.545
			0.861 0.715 0.019 – 0.139 0.015 0.001 +1.556 +1.545 0.002 0.003 0.002 – 0.002 0.001 0.000 0.007 0.011
	2	R	8/4 5/3	+1.456 ( -0.089)
			0.867 0.559 0.009 – 0.133 0.008 0.000 +1.385 +1.456 0.001 0.003 0.001 – 0.001 0.000 0.000 0.005 0.007
	3	R	8/4 6/4	+1.434 ( -0.111)
			0.864 0.537 0.009 – 0.136 0.008 0.000 +1.351 +1.434 0.001 0.003 0.001 – 0.001 0.000 0.000 0.005 0.008
	4	R	8/6 8/4	+1.391 ( -0.154)
			0.868 0.574 0.010 – 0.132 0.005 0.000 +1.408 +1.391 0.002 0.003 0.001 – 0.002 0.000 0.000 0.006 0.010
	5	R	8/6 5/1	+1.319 ( -0.226)
			0.826 0.494 0.008 – 0.174 0.010 0.000 +1.224 +1.319 0.002 0.003 0.001 – 0.002 0.000 0.000 0.006 0.009

Staying Connected

 

At this point I don’t have any positions to discuss on this topic. The positions in Trice seem pretty self explanatory and I am not sure at this point that I can correctly apply this concept to a match position for discussion. I have, however, after reading this chapter been attempting to keep the whole concept of connectivity in mind during actual play. I will come back to this subject when I feel like I have something more to add.

Premature Burial

 

The concepts in this chapter are fairly easy to grasp, I think for us lower level players there are really two issues we have to come to grips with when dealing with this topic, one is the fear of leaving a blot or blots and the other is knowing when to make an exception to the general rule and place a checker on the one or two point.

Pip counts: Blue 157, Red 167
Position ID: 4HPhQSDgc/ABMA Match ID: cAkVAAAAAAAA

Hits in the home board are sometimes an exception to the premature burial rule. In the above position I would be inclined to play 13/8 24/22 or 13/8 13/11 to avoid burying a checker on the ace point. However a rollout (648 games, expert) gives the best play as 5/1* 24/22 followed by 5/1* 13/11.

Game Plan

 

This is another of those areas where the real trick for me at least is learning to think in terms of a game plan as the game progresses. I often find myself making a move that seems right only to realize that I have created some long term issues for myself. I think this is often due to failing to make the play with a view to an overall game plan. For example in position 2-1 I might well have continued to try a priming approach without really thinking about the long term problems with that play.  Hopefully I will begin to think in terms of a game plan when playing in the future.

For further study on game plans Gammon Life has a series of articles by Mary Hickey devoted to the topic of game plans. You can find them at http://www.gammonlife.com/writers/maryhickey.htm. 

There are also several articles by Walter Trice that deal with game plan issues on the same site http://www.gammonlife.com/writers/waltertrice.htm.

To Hit or Not to Hit (Part 3)

Positions 1-30 through 1-33 illustrate the 6 criteria Trice discusses for deciding between safe and bold plays. I find that remembering “boards, backs, blots, anchors” is a good way to keep in mind what needs to be considered in these situations. The real trick is remember to apply this criteria in the course of play. One of the the things I am struggling with right now is making sure I am thinking about all of this in the course of a match.  Position 1-30 is really close, so playing the hit while not the best move is not a devastating error.

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#		Ply	Move	Equity
•	1	R	15/13 6/5	-0.314
			0.416 0.086 0.004 – 0.584 0.144 0.004 -0.227 -0.314 0.002 0.002 0.001 – 0.002 0.002 0.000 0.006 0.017
	2	R	8/7*/5	-0.342 ( -0.028)
			0.415 0.130 0.008 – 0.585 0.211 0.012 -0.256 -0.342 0.003 0.002 0.001 – 0.003 0.003 0.001 0.007 0.021

Before I leave the subject of To Hit or Not to Hit I would like to show a position I encountered playing GNUBG the other day. I was surprised at the best play in this position, and I am still not sure I can articulate why this is best. But here is the position:

 

Pip counts: Blue 71, Red 82
Position ID: t+0GABBz20ZAAA Match ID: QokIAAAAAAAA

My play was 10/7.  If red gets hit at this point it is pretty much game over, so my thought was that I had to play it safe. Even though I am behind in the race blue still has to roll a 6 to get their back checker moving, and even then with the exception of 66 I am still likely to get a shot and maybe a direct shot at it. 10/7 gives me a chance to make the 2 point on the next roll (although a slim one).  After 10/7 the next roll seemed pretty safe, although their are rolls that would leave an indirect shot for blue or force red to break a point in their home board.

The surprising (at least to me answer) is:

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#		Ply	Move	Equity
	1	R	17/15 3/2*	+0.313
			0.705 0.021 0.000 – 0.295 0.081 0.001 +0.350 +0.313 0.001 0.001 0.000 – 0.001 0.001 0.000 0.003 0.005
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 868089133 and quasi-random dice
			Play: 0-ply cubeful [expert]
			Cube: 0-ply cubeful [expert]
	2	R	10/8 3/2*	+0.296 ( -0.017)
			0.739 0.022 0.000 – 0.261 0.124 0.003 +0.373 +0.296 0.001 0.001 0.000 – 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 868089133 and quasi-random dice
			Play: 0-ply cubeful [expert]
			Cube: 0-ply cubeful [expert]
•	3	R	10/7	+0.152 ( -0.162)
			0.628 0.015 0.000 – 0.372 0.013 0.000 +0.258 +0.152 0.001 0.001 0.000 – 0.001 0.001 0.000 0.002 0.004
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 868089133 and quasi-random dice
			Play: 0-ply cubeful [expert]
			Cube: 0-ply cubeful [expert]

After 3/2* red as just over a 30% chance of getting hit. Virtually all of these will be wins for blue (given the winning percentages from the roll out red will run a few games even after being hit).

So what is wrong with the “safe” 10/7. After playing out the position a few times the problem for red is that if blue rolls a 6 fairly quick there are a lot rolls where blue gets a shot at the red checker as it comes around from the 17 point.  Blue may get a few chances at the red checker, so the hit comes out to be the best play.