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Holigors Rant On Yose
   

I looked at the Yose page and found a great advice to learn to calculate the value of the yose moves (slowly, in several years).

It seems to me that I play the game for ages and yet learning the skill of yose calculations is ever postponed. I think that you would agree that yose is usually played by tired players. I, for instance, don't usually have stamina to start making necessary calculations. Moreover, the calculations have to be performed fast. Yet, I know that I did not actually do my homework on yose, I am not prepared and I don't know the values of the basic moves. Moreover, quite often I am not even concentrated enough and let points go because I don't see the moves. It seems that the result of the games fluctuates quite significanlty in the endgame.

And yet, I have an impression that my performance in yose is not that bad and quite often I gain a lot at this stage of the game. Could it be that my opponents are even worse. Of course, some are better than me but most are not good at all.

I don't know the values of the moves but I don't reply automatically at least.

So, I would like to make myself a library of some most common yose moves. I think that if you know what is the value of some moves your task is simpler because you'd be able to miss that part.

I believe also that a library like this will be most useful for the person that compiles it. Actually, the most important task is to learn the way the calculations are done. It seems that once you've made some calculations then have a certain know-how.

[Diagram]
Diag.: Zero position

Black has 6 points, white 3. The score is +3.


[Diagram]
Diag.: The score is not changed

White has a one-point ko-threat at 'a'. Black marked stone is the correct reply to white's marked stone.


[Diagram]
Diag.: White can get one point more on ko.

Thus we have to conclude that the position has a 0.5 value miai counting. One has to be a ko master to get an additional point playing at 'a'. 'b' serves as a one point ko-threat.



BillSpight: A play at 'a' has the same value as playing a ko where the ko stones are the only thing at stake, 1/3 point (miai).

[Diagram]
Diag.: One-third point play.

If White plays first, through B 4 Black has 2/3 point in the corner, 1 point for the captured stone minus 1/3 point for the stone in atari. If Black plays B 1 instead, he gets 1 point at 2. A net difference of 1 play makes a difference of 1/3 point.



[Diagram]
Diag.: The value of 'a' (4.5 points miai counting)

Black 'a' brings it to zero position. Score +3. If white plays 'b' the following produces


[Diagram]
Diag.: White's move

As the result white has 7 points, black 1. The score is -6. The average local score is -1.5 point with the value of a move 4.5 point miai counting.

This is the first large result and I don't have anything to make comparison with, but it can serve as a reference point.


[Diagram]
Diag.: The value of 'a' (3.75 miai counting)

White's 'a' raises the local temperature to 4.5 points. Black's 'a' makes the score equal to +6 with 0.5 point temperature. White 'a' reduces it to -1.5 position with 4.5 temperature.

Now, I don't know how to count here. The value of the move cannot be less than the temperature of the resulting position, right? So it is 4.5 points miai counting. Black 'a' increases the score to 6 points and cools the position down to 0.5 point. White 'a' makes the score equal to -1.5 points while keeping the temperature high (4.5 points). So, average local score is 2.25. A move a 'a' increases it by 3.75 but it is not symmetrical since white's move keeps the temperature high.



BillSpight: On the reasonable assumption that White has territory on the left side (as marked above), after B a, Black will have a 1 point sente to play inside that territory. In that case the play at a is a 4 point sente for White.

[Diagram]
Diag.: 4 pt. sente

The value of a sente is the difference between the position after the sente and reply and the position after the reverse sente. After the reverse sente (marked) B 1 - W 2 is Black's sente. The reverse sente picks up the 3 marked points plus the point at 2.



Can one say that if the temperature is not the same after the move the move is considered sente/gote. Sente is a relative notion after all.


BillSpight: Sente has more than one meaning. In the local sense, W 1 raises the temperature, and Black should respond. However, since it raises the temperature only 1/2 point, it is not hard to construct whole board positions where White should play W 1 but Black should then play somewhere else and let White continue locally. :-)


[Diagram]
Diag.: Black 1 is worse

White can play 2. After 3 and 4 black cannot connect. He will have to play on the marked point and then white can fight a two point ko.



Actually what I am interested in is not a 1-2 point yose. It is not easy to get much on that but a big yose, when the untrained eye does not see the difference between 6 point moves and 8 point moves. Being able to play this correctly would make difference in a game.


BillSpight: In modern (post 1900) pro games you see occasional game-losing yose errors at around 3 points. Errors that lose a point or two but not the game are fairly frequent. You are right that the important yose to get right are the medium and large yose. :-)
This relates to your point earlier about having time to calculate (estimate) the size of yose. High-level go games of 200 - 300 years ago had very few yose errors. The pace was slow and they took the time to work plays out. IMX, the time to figure the (approximate) size of yose is when you tenuki.
After all, the main reason to play somewhere else is that it's a bigger play. (The proverb about urgent moves before big moves is really about seeing how big the urgent moves are. :-)) So when you leave an area you already have some idea of how big it is: not big enough. Take a few seconds and ask, What is my follow-up here? What is my opponent's follow-up? Local sente or gote? Compare the results and estimate the size of the play. You will usually be within a point or two, which is usually good enough to order plays reasonably well. By the time you come back to consider the play, the surrounding conditions may have changed the size of the play substantially, but usually your original estimate is good enough. Don't wait until you are tired to make these calculations.
Of course, novel positions will arise, but you will already have a good idea of the size of many plays. :-) In addition, such calculations will help you assess the state of the game.


[Diagram]
Diag.: Zero position on the side

White has 8 points, black 5, score is -3.


[Diagram]
Diag.: Unfinished position

White 'a': score -3. Temperature 0. Black 'a': score -2. Temperature 1. Value of the move 0.5 point. Local score is -2.5



BillSpight:

[Diagram]
Diag.: Sente follower

W 2 elsewhere.

After B 1, B 3 - W 4 is sente. If White replies at 3, she gets a point at 4, so it is a 1-pt. sente. If White plays at 1, she gets 2 points at 3 and 4. By comparison with a White play at 1, B 1 gains 2 points in gote or 1 point in sente. Both alternatives yield the same miai value: B 1 is ambiguous, with a miai value of 1.



But the question about the temperature remains. The value of the move is bigger than in the case when white had a stone at 'b'.


Bill:

[Diagram]
Diag.: Half point

After B 1 there is only a dame left. If White plays at 1 he makes 1 point. So this is a 1/2 point gote (miai).



The most difficult about this is the inability to reduce it to known positions.



This is a copy of the living page "Holigors Rant On Yose" at Sensei's Library.
(C) the Authors, published under the OpenContent License V1.0.