Taiwan rules

The "Taiwan rule", is a--now seemingly uncommon--practice of removing the last played stone if it was played by black. (Applicable to area scoring rules prior to scoring a completed game.) This preserves an equal number of moves between players, having an intuitive, if modest mitigating effect of the advantage of black playing first (pre komi). This rule is not a feature of ING rules that are today associated with Taiwan (see discussion below).

Historical Precedent: Chen Zuyuan, in his article The History of Go Rules (2011) makes the argument that an equal number of moves by black and white was an original prerequisite of play that has almost entirely been discarded over time. He uses his interpretation of ancient go texts and early preserved game records to support this claim.

Modern Manifestations in rule sets:

• Ikeda Area Rules III, Inspired by the "Taiwan Rule"
• World Mind Sports Rules
• Button go

A non-example--or rather a reverse example--is the AGA rule requiring an even number of moves/passes, with a cost of one prisoner per pass. Ironically, the purpose of this rule is to reconcile territory counting mechanics with area scoring that doesn't mandate equal number of moves, penalizing white in territory for passing first, to arrive at an identical score.

Discussion [Charles Matthew s]: I presume that reference to Taiwan rules can be taken to be the SST (Ing) rules. But since this area is a minefield ... perhaps someone can explain why I'm wrong.

Bill: No, that reference is to the Taiwan rules as they existed before they adopted Ing rules. Ikeda refers to them in On the Rules of Go, Section 3.6.

Ikeda writes:

Instead of talking about filling the last neutral point, we can say with slightly greater generality that half a point is deducted from Black's score and added to White's score whenever Black makes the last competitive move. This rule, known as the Taiwan rule, is an extremely interesting modification of area rules. In formulating this rule, the key problem is how to define the last competitive move. A concise but complete definition would be highly significant; it would put the finishing touch on area rules.