Real Half Point Ko
As a rule, there will be no smaller plays between this ko and dame, so that the only question is who wins the ko, and it will behave as though it were a half point ko.
Black wins the ko with , unless that is ko-banned in which case Black wins the ko with . Either play is sente and White responds at .
In the end White will net only 2 points of territory locally.
A net difference of two plays in the ko makes a net difference of one point. Each play has a miai value of 1/2.
This ko also has a miai value of 1/2, unless Black is komaster.
A difference of two moves makes a difference of one point, so the miai value of the ko is 1/2.
elsewhere. - = ko threat and reply. takes ko back. elsewhere. at .
Again, a difference of two plays makes a difference of one point. Miai value of ko = 1/2.
When Black is komaster the ko has a miai value of 7/12.
elsewhere. takes ko. - = ko threat and reply. takes ko.
Result: +2/3. (Black has taken one stone for one point, minus 1/3 point for the black stone in ko.)
After the local temperature drops to 1/3. Black has a sente sequence with - .
Two plays make a difference of 1/2 + 2/3 = 7/6 points. The miai value of the ko is 7/12.
-- Bill Spight