Using reference positions

Having studied the appropriate cube action for a variety of position classes (such as holding games or blitz games), we have clear instructions for cube handling in a set of well-defined situations. In this article, we will learn how we can use these positions as reference positions to dramatically expand the domain in which our we apply our newfound cube judgement. Though we’ve discussed this concept briefly in previous articles, it’s worth dwelling on a bit now that we have the appropriate background to appreciate it.

Consider this position below:

This is reminiscent of the double 3 blitz that we discussed in our article on blitz cubes. However, when directly comparing to that position, we notice that our present position has a meaningful improvement: instead of only having the 8 starting checkers in the zone, we now have 10. This contributes enough to our standing that the right cube action blows past the D/T from the previous position into D/P territory.

This “position adjustment” analysis can actually go both ways. The position below also resembles the double 3 blitz, but with a different adjustment:

Here, before we attempted our blitz, Gary was able to snag his 5-pt. He’s still got a checker on the bar with a loose blot in his home board, and we still have a 3-pt board, but despite these threats, his position is meaningfully stronger. This change is sufficient to delay us from offering a double! The current cube action here is ND.

Most positions encountered in a real match will have multiple differences from the references we have learned about. However, we can often still accurately determine the cube action for a variety of positions using a simple tally scheme: we compare all the different features of the position to a known reference, adding 1 to the tally for each improvement to our position, and subtracting 1 for each improvement to Gary’s. The final tally measures roughly how different a position’s strength is when compared to a reference. If the net tally is 0, we have the same cube action as our reference! If the reference is for a D/T position, and our tally number’s large and positive, it’s probably a pass; if it’s large and negative, then it’s not a double.

In the position above, we included both of the adjustments discussed in this article: we have 10 checkers in the zone and have given Gary his 5-pt. Combined, your tally balances out, meaning we have recovered the D/T cube action of the reference position.

Finally, we present an example of the tally system at work in a holding game position:

We know that we should not consider cubing in a holding game until we have 4 or fewer checkers remaining on our midpoint. Having 5 checkers, as we have here, is a weakness to our position. However, Gary hasn’t managed to anchor up his backcheckers yet. He has a weakness as well! The two weaknesses roughly cancel out, therefore matching the reference, resulting in a D/T.

Further reading

• A classic article by Kit Woolsey studying a standard 5-pt holding game and exploring what adjustments to the position make for meaningful changes.

Next lesson: Doubling in… everything else (O’Hagan’s Rule)