Cash game, center cube.
Should White double? Should Black take if doubled?
Problem 172 is a position type that we’ve categorized as ‘One Man Back’. White has escaped both his rear checkers, while Black still has one man in White’s home board. Now White is considering a double. What factors go into the evaluation of a double in these positions?
As in most positions, the first item on our list is the race. Here White has a solid 10-pip lead, 122 to 132. When we talked about races, I described the 8-9-12 rule for evaluating pure races without contact: make an initial double with at least an 8% lead, make a redouble with at least a 9% lead, and take the cube if you’re trailing by no more than 12%. This is a simple but effective rule that covers most positions where the leader’s pip count is in the 70-130 range.
If we ignore the contact and apply the 8-9-12 rule to this position, we find that White is just barely in double territory. His pip count is 122, and 8% of 122 is just less than 10. White’s 10-pip lead would be just enough for an initial double in a non-contact race. Black, of course, would then have an easy take.
Here, however, we have contact, and that contact strongly favors White. He has nine rolls that point on Black immediately (42, 43, 32, 44, 33, and 22), and those rolls make White a very big favorite. He also has a couple of pick-and-pass numbers (31 and 21), which turn bad racing numbers into pretty good shots, as well as a switching number (11). With his big numbers being great for the race and his small numbers putting Black on the bar, White’s position is much stronger than a simple race count would indicate: he has a very strong double, and Black should pass.
In general, a single checker back is a weakness rather than a strength. The opponent (White in this case) has the option of sitting on his position and trying to win the race, but he also has the possibility of attacking or priming when his rolls allow it. As a result, Black has to try and convert the game into a pure race as quickly as possible. In general, he can’t passively stay back; he’ll jump into the outfield when he can, but he’ll also move up in White’s board when possible, even at the cost of allowing White a few pointing numbers. Time is not on the defender’s side in a ‘One Man Back’ situation.
How small a racing lead does White need to double? Actually, he doesn’t need a lead at all! His multiple threats allow him to double even when trailing in the race. Let’s take a look at Position 172B, where we’ve moved one Black checker from Black’s midpoint to his 2-point, leaving White trailing in the race by one pip:
Position 172B: White on roll trails by 1 pip, 122 to 121.
In this position White’s immediate threats still leave him with a solid double despite now trailing in the race. Black now has a very easy take, of course.
