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While the take-point for a money game is 25% (unless gammon risks are too high), it varies according to the match score.
Red has doubled to 2, White's take/pass decision Pip counts; White 105, Red 95 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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For money, this is a border line double for Red and a trivial take for White. On the race alone, Kleinman's pip count formula shows that White wins 24% cubeless (1% fewer than his take-point for money), but White's small hitting chances plus Red's potentially vacant or thin 5-point (when it turns to a simple race) gives White 27.5%~ cubeless winning chances. This can be another story at a particular match score. Let's see White's take-point at a somewhat tricky score of 9-away (White) vs. 4-away (Red). We will see what happens from White's point of view (based on W/H Met). White passes: 9-away, 3-away, 16% equity. White takes and loses: 9-away, 2-away: 9% equity. White takes and wins: 7-away, 4-away: 30% equity. White risks 7% in order to gain 14%, so his take-point is 33.3% cubeless. It is obvious that White cannot win 33.3% cubeless from this position, so is it a pass for White? No, way. We should take White's recube chances into account. If White hits Red or White rolls sets of doubles and becomes a favorite in the race, White will recube to a 4. Also, if Red takes that recube, he will be sitting on a dead cube. Now, let's see Red's take-point on a 4-cube from Red's point of view. Red passes: 4-away, 7-away: 70% equity. Red takes and loses: 4-away, 5-away: 58% equity. Red takes and wins: wins match: 100% equity. Red risks 12% in order to gain 30%, so his take-point is 28.6% cubeless. White's recube efficiency is probably a bit higher than 70% since this is a medium race basically, but to make it simpler let's assume White's recube efficiency as 70%. This makes White's take-point 26.7%. The formula to calculate this is as follows: While this is a borderline money double for Red (probably not good enough), Red can use 2 or 4 points quite efficiently at this match score (4-away, 9-away), which makes his double a bit more justified. (Note that GNU often overvalues holding games in its evaluations, while SW4 evaluates this sort of position relatively correct.) Meanwhile, this is an easy money take for White, but at this match score White needs higher (+1.7% with 70% recube efficiency) cubeless winning chances in order to take. While it might be helpful to memorize take-point for all scores up to 15, I memorized only 1/3 of them with no gammon chances. I memorized trailer's take-point at this match score, but OTB, I would also make a quick judgment that White has a trivial take in this position as follows: 1) Does White win 30% cubeless from here? -- Doubtful, because White trails by over 10% of Red's pip-count. 2) Does White win less than 25%? -- Clearly not, because the contact favors White slightly and in some variations Red will waste pips for the safe bearin and also have difficulty filling in his 5-point when the game turns to a simple race. 3) So White wins between 25% and 30% cubeless: (25+30)/2 - 0.5 (race deficit: 10 - 9.5) = 27% 4) White wins roughly 27% cubeless from this position, and White has substantial recube vigorish though it can be counterbalanced by the fact that Red can use 2 or 4 points very efficiently, so the match score slightly favors White. 5) 3) + 4) gives White a clear take. [Jul. 04 / Hisako] |
