When counting area (chinese style), AGA rules Komi for N stones handicap games is always N - 0.5. Thus:

Even game : 7.5 komi

“One stone” game: 0.5 komi

Two stone game: 1.5 komi

Three stone game: 2.5 komi

Four stone game: 3.5 komi

…

These values are chosen precisely because they keep the mathematical theorem that counting area or counting territory (with passing stones) will lead to identical result (komi is always 0.5 for handicap games under AGA rules IF you are going to count territory).

Now, what are the values for CHINESE rules komi, for the case of ONE STONE games? I am not able to find a reliable source by googling and I am not sure whether they are 1.5 or 0.5. For 2 or more handicap, it is clear that Chinese komi for handicap games is N + 0.5 (simply "add one extra point per handicap stone).

So it is:

Even game : 7.5 komi

"One stone" game: Either 0.5 komi or 1.5 komi - which one is it? That is my question

I don’t know what the official Chinese rules say, or what the common practice is outside of OGS, but I believe OGS uses 1.5 komi for “one stone” games.

The discrepancy between AGA and Chinese rules is minor. However, New Zealand rules (as implemented on this server) are quite different in not increasing komi at all for handicap stones (although there is a display bug that seems to imply that it does).

In the most strict Chinese rule, the counting isn’t done with comparing the area difference “between” two sides, but compare one side with half of the total intersections (a base number in 19x19 it is 180.5, 9x9 it’s 40.5, etc.), and the result is reported as how many “zi” (子) winning compared to the half base number.

So in a no komi (讓先) game, if one side gets 181 and the other side 180 area, it would be just one side wins by 0.5 zi. And in the case of seki (with odd number of shared liberties), it can be a draw. The same goes for handicap games, the side getting handicaps has to return half the amount of handicap zi (stones), so 2 handicaps 1 zi, 3 handicaps 1.5 zi, 4 handicaps 2 zi, etc.

What you asked about the difference between return 1/4 zi (0.5) and 3/4 zi(1.5), in a “no komi” game isn’t a proper question at all, since it would be technically a game with “komi”.

In actual tournament in order to make draw not possible, there is usually an additional rule added like “和棋白勝” (when a game is draw, white wins).

I understand the Chinese traditional counting method (“half counting”) and reporting the result traditionally as the number of controlled intersections difference to “half the total score”, I just expressed everything in terms of “points” when directly counting area (controlled intersections) as I think most people in the west are familiar with that idea.

Yes, exactly, this is the part I know. Adding 1 zi to white score and subtracting 1 zi to black score to allow half counting has the same effect as counting “the direct way” and giving white two extra points, which I included into komi for simplicity. I understand now that you are emphasizing that this compensation should be considered completely unrelated to komi, in order not to mix them up. Which makes sense because you say there there can be draws, so basically these are “no komi” games?

Oh I think that I understand. You mean that a handicap game is basically a “no komi” game. So actual komi would basically be “0”. But surely there is the standard “tie breaker” that white wins ties? So the effective, “western style” table would actually be:

Even game : 7.5 komi

“One stone” game: 0.5 komi (this komi is just the tie breaker)

Two stone game: 2.5 komi (the 0.5 is just the tie breaker)

Three stone game: 3.5 komi (the 0.5 is just the tie breaker)

Four stone game: 4.5 komi (the 0.5 is just the tie breaker)

Which in mathematically equivalent (always has the same result), but proper Chinese “traditional half counting” terms, would be:

Even game : komi is 3,75 zi (add to white, subtract to black. Already includes tie breaker)

“One stone” game: no komi

Two stone game: 1 zi “compensation points” (not actually komi, but same effect for calculation)

Three stone game: 1.5 zi “compensation points”

Four stone game: 2 zi “compensation points”

…

And, in all cases, white wins ties would be the standard tie breaker (I think so at least…). Did I get it right?

I just want to add that if we go back hundreds of years when group tax was still in used, the return of half of the handicaps also didn’t exist. Back then, in handicap games, white needs to be even more aggressive in cutting smaller groups of black (well, technically to the one play first, since during one time period, white played first)

I think it’s one of the reason why some ancient Chinese game records don’t make much sense to us using modern rules, and why ancient players were so aggressive and seemed to “overplay” in our point of view.

An additional note. The exact time when the rule emerged for returning a certain amount of stones in handicap games is not clear (at least I am not. If someone has access to more ancient handicap games with scoring results, please share them with us, I only saw a few of them have complete handicap games like 寄青霞館弈選, 海昌貳妙集, etc. Books like 三子譜 四子譜 usually don’t have scoring results).

I know books supposedly composed games in the 18th or early 19th century (but they were usually collected and published in late 19th or early 20th century), they would give the exact same amount of stones in handicap games (2 zi for 2 handicaps, 3 zi 3 handicaps, etc.). But for collections that include games earlier than 18th century (like a game from Legend of Blood and Tears with Huang Longshi), it will be literally impossible for those games to have any return stones for handicaps (half or otherwise).

It does make some sense for handicap games to return the same amount of stones if the core concept was not area scoring, but stone scoring mixed with every group has to have two eye space (group tax). It would not be one side has more areas, but how many stones each side can survive on the board to the very end (filling all but 2 eyes), since if one side plays several stones first as handicaps, the other side would be given the same amount back to have equal amount of stones/hands for a “draw”. And it probably would be easier to “count” manually without any fractions involved.

My best guess is that prior to the 17th century, the rules were probably quite flexible and most likely have regional differences (counting the road with group tax, similar to territory scoring might still exist). But during the 18th century, when several very strong players emerged, they started to focus more toward the core concept of counting the stones to make game rules more logical and consistence, and the top players had the new consensus in returning stones for handicaps (with cheaper and more advanced printing technologies their influences also spread wider). Only when much later in early 20th century, the modern concept of area scoring started to take shape due to interaction with Japanese players (the rules of returning half handicaps along with removing the group tax were settled even further down the line in mid-to-late 20th century)