Before the players end the alternation by passing, usually they fill enough dame to motivate the opponent to fill teire so that the opponent does not have territory on teire intersections because of surrounding them with his independently alive strings. (This presumes that, if necessary, the analysis would be performed competently. The rules permit incompetent performance. There is also the possibility of value-symmetries where unfilled teire would "accidentally" create the same score.)Pio2001 wrote:If I understand them properly, there is no point in filling the teire if the players passed their turn, the empty intersection in the last ko, if not connected, is worth one point of territory, and if a four bent remains together with a small seki, the four bent, being proven dead, is removed while the seki remains on the goban ?RobertJasiek wrote:http://home.snafu.de/jasiek/sj.html
If there is exactly one unfilled basic endgame ko at the end of the alternation, it depends on how the players perform the analysis. Competent play in the analysis without ko fight means that the ko is either filled by the defender moving first in the analysis or captured-then-filled by the attacker moving first in the analysis. The defender's ko stone would thus be proven as independently alive while the attacker can establish his two-eye-formation but thereby not prove any ko stone of his as independently alive in the position at the end of alternationn because the attacker does not have any such string in the ko in that position. Incompetent play can lead to a different assessment of the defender's ko stone. Since there is such variety of considerations involved including a ko fight during the analysis, one or both players can be expected to prefer avoiding this by winning and filling the ko already during the alternation. Positional superko means that rare positions can occur in which not filling the last basic endgame ko is correct strategy because the opponent does not have any legal play; then the defender can postpone filling the ko until the analysis to prove the ko stone's independent life and the empty ko intersection's territory in the position at the end of the alternation in only these rare cases; such a game has been reported once for 9x9 (and might occur there at times) but is inconceivable for 19x19. EDIT: There is also the possibility of winning the ko fight during the alternation, the opponent passing because of having no dame and not wishing to fill territory (losing 1 point by doing so), during the analysis the opponent may still not recapture due to positional superko, the player creates independent life and so proves one extra territory intersection in the ko. This case occurs in ca. every 20th game and means that the rules are not for traditionalists; they might prefer to avoid superko (for various other reasons, too).
Bent-4 and seki can lead to different results depending on the exact shape and the global ko threat situation. I am too tired to work out now whether some such shapes should not be dissolved during the alternation.
EDITED.
