I'm curious to hear some explanations on this one. White is leading the 5-point match 1-0, pip count tied at 126. Does white double? Should black take?

White has an very large and obvious positional edge here and should double.

Even though Black is down in the match, he should be conservative at the score. This 4-away score for White is worth noting. A gammon puts him exactly at what he needs to win the match, so White's many gammons are especially valuable. And by passing Black saddles White with an awkward 3-away score.

So even if this is a take for money (unclear, yes?), he should pass at the score.

I remember something Kit Woolsey wrote about years ago regarding 4-away scores. A one point difference in a match matters more when the match is short. You'd rather be ahead 2-away 3-away than 11-away 12-away.

And when the modern bots came out with their match equity tables determined by rollouts, this heuristic held of course. Except in one case it's flipped. You'd rather be ahead 4-away 5-away than 3-away 4-away!

4-away is particularly nice. Obviously if it's a choice between being 3-away and 4-away, you'd always choose 3-away, but the gain from getting to 4-away is bigger than you'd think and the gain from going from 4-away to 3-away is smaller than you'd think.

Edit: ooh found the article -- http://www.bkgm.com/articles/GOL/Jan01/sneq.htm

Interesting; appreciate the explanation. It seems my biggest cube blunders lately are due to not understanding match equity. In this case, the 25% gammons (that I didn't see) I'm assuming is reason enough to drop, notwithstanding the positional advantage white enjoys. Thanks for the link to the Woolsey article - exactly the kind of stuff I need to study.

A great article also from Woolsey on match equity:

http://www.bkgm.com/articles/GOL/Aug99/fivept.htm

Here's another position where this 4-away concept is relevant. Pretty solid money pass, but leading 2-0 in a match to 5, Black should take so he doesn't let White get to 4-away.

Even in cash games, when your opponent has a high gammon equity you have to take that into account. In a cash game, the take point is usually around 21.5% due to cube vig.

To figure out your equity with a high gammon vig that your opponent has, you have to multiply the net gammon % by 50% and add that your your equity required for a take.

Here he has 18% gammon vig, (his gammon % - your gammon %) so you have to add 9% (18% * 50%) to your take point. So in a cash game, you have to win a little over 30% of the time to have a take. So even in a cash game this is a pass.

To find your take point in a match use the match equity tables. Kit Woolsey's is not the most accurate. The Rockwell/Kazaross MET are the tables that most of the pros use currently.

Your take point at this score is 24%. But now his gammon vig is even higher than a cash game, because by activating the cube, his gammons win the match and he gets full value for his gammons. So without doing the math, I know you need more than an additional 9% here and maybe as much as 12% additional games won to make up for his gammon equity. So you probably need somehwere around 36% wins before this is a take ATS.

Here are the Rockwell/Kazaross tables:

http://www.bkgm.com/articles/Kazaros...MET/index.html

And a good shortcut to use to estimate your equity over the table:

http://www.bkgm.com/rgb/rgb.cgi?view+171