Reviewing a 1971 Otake game with Kata

xela · **#41**

Thanks, I really enjoyed going through this game! I too struggled to understand the status of the white groups on the right at various times. And :w98:

was a neat tesuji. But for me the most surprising move of the game was :w72:

.

Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . O . . . . . . . . . . . | $$ | . . . O . O . . . . . . . . . . O . . | $$ | . . O . . O X . X . . . . X . X X . . | $$ | . . O X . . X . . . . X . . . . X . . | $$ | . . X . . . . . . . . b . . . O O O . | $$ | . . . X . . . . . . . . X . X . . . . | $$ | . . . . . . . . W W W W X . . . O . . | $$ | . . . . . . . . W X X X O O O O . X . | $$ | . . . . . . . . . . . . X . X . . O . | $$ | . . X . . . . . W . X . X . . . . O . | $$ | . . . . . . . . . . . . . . X X X X . | $$ | . . O . X . . . . . . . O O . O . . . | $$ | . . . a . . . . . . . . X O . . . O . | $$ | . . . . . . . . . . . X . X . O . . . | $$ | . . . O . . . . . X . . X . . O . O . | $$ | . . . . . . . . . . . . X . X X O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ +---------------------------------------+[/go]

I thought a move to strengthen the centre group was pretty much essential at this point. But no, Otake fearlessly played a! KataGo does indeed prefer a move in the centre (and has several suggestions, not a single clear favourite), but thinks that the game move is still playable (white's lead drops to 2 points). In many variations, white has b as a saving move.

That :w98:

is a "+11% move" for my KataGo 1.3 setup. That is, KataGo doesn't find the move, but when I put it on the board, the winrate is 11% above KataGo's first choice. Also, :b89:

is +8% (KataGo just looks at the clamp instead), and :w90:

is +4%. With these apparent blind spots, I agree that we can't trust KataGo's evaluations of other moves round about this part of the game. In particular, I don't think we can conclude that :w94:

is actually a blunder.

In hindsight, after seeing :w98:

I wondered if :b85:

was a mistake. But any alternatives appear to be even worse.

Earlier, I'm pleased to find that I seem to have learned something from Genjo-Chitoku: I was able to recognise :b17:

as creating momentum for :b21:

(although KataGo isn't overly impressed by :b17:

and prefers a pincer for once).

xela · **#42**

Bill Spight wrote:

There is a remarkable discrepancy between the winrate estimates of KataGo and the Elf commentary. As we know, Elf tends to favor Black by comparison with other bots, at least at first, and its evaluations tend to be more extreme than other bots'. However, at move 181, where a ko fight breaks out, KataGo gives Black a 61% winrate estimate, at that same point, Elf gives Black only a 24½% winrate estimate (with 47.5k rollouts), a discrepancy of 36½%, not counting the original difference at move 1. :o

Not at all remarkable. Remember that KataGo can work with the correct komi in these old games, but ELF can't. On 10k playouts, I'm seeing Black at +61% or +0.8 points in KataGo with komi=5, or +47%, +0.3 points if I edit the SGF file to the correct komi of 5.5. With the position so finely balanced (and late enough in the game that score estimation should be pretty accurate), it's no surprise that an extra two points of komi will change the winrate a lot.

Bill Spight · **#43**

xela wrote:

Bill Spight wrote:

There is a remarkable discrepancy between the winrate estimates of KataGo and the Elf commentary. As we know, Elf tends to favor Black by comparison with other bots, at least at first, and its evaluations tend to be more extreme than other bots'. However, at move 181, where a ko fight breaks out, KataGo gives Black a 61% winrate estimate, at that same point, Elf gives Black only a 24½% winrate estimate (with 47.5k rollouts), a discrepancy of 36½%, not counting the original difference at move 1.

Not at all remarkable. Remember that KataGo can work with the correct komi in these old games, but ELF can't. On 10k playouts, I'm seeing Black at +61% or +0.8 points in KataGo with komi=5, or +47%, +0.3 points if I edit the SGF file to the correct komi of 5.5. With the position so finely balanced (and late enough in the game that score estimation should be pretty accurate), it's no surprise that an extra two points of komi will change the winrate a lot.

Oh, right.

I was not figuring in the different komi settings.

Viva KataGo!

Bill Spight · **#44**

xela wrote:

Earlier, I'm pleased to find that I seem to have learned something from Genjo-Chitoku: I was able to recognise :b17:

as creating momentum for :b21:

(although KataGo isn't overly impressed by :b17:

and prefers a pincer for once).

Remember that the value of pushing or jumping through an opening is as a rule better the smaller the opening is. Jumping through a 5 space opening is not a big deal. In fact, for :b21:

Elf prefers the jaw jab at R-10 by 3½% to the jump. Curiously, Elf prefers the jump for :b17:

, but only by 1% over the kick.

xela wrote:

But for me the most surprising move of the game was :w72:

.

Click Here To Show Diagram Code: [go]$$Wc $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . O . . . . . . . . . . . | $$ | . . . O . O . . . . . . . . . . O . . | $$ | . . O . . O X . X . . . . X . X X . . | $$ | . . O X . . X . . . . X . . . . X . . | $$ | . . X . . . . . . . . b . . . O O O . | $$ | . . . X . . . . . . . . X . X . . . . | $$ | . . . . . . . . W W W W X . . . O . . | $$ | . . . . . . . . W X X X O O O O . X . | $$ | . . . . . . . . . . . . X . X . . O . | $$ | . . X . . . . . W . X . X . . . . O . | $$ | . . . . . . . . . . . . . . X X X X . | $$ | . . O . X . . . . . . . O O . O . . . | $$ | . . . a . . . . . . . . X O . . . O . | $$ | . . . . . . . . . . . X . X . O . . . | $$ | . . . O . . . . . X . . X . . O . O . | $$ | . . . . . . . . . . . . X . X X O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ +---------------------------------------+[/go]

I thought a move to strengthen the centre group was pretty much essential at this point. But no, Otake fearlessly played a! KataGo does indeed prefer a move in the centre (and has several suggestions, not a single clear favourite), but thinks that the game move is still playable (white's lead drops to 2 points). In many variations, white has b as a saving move.

Elf also prefers to play in the center rather than at a. In fact, it prefers b over a by 15½%.

xela wrote:

That

is a "+11% move" for my KataGo 1.3 setup. That is, KataGo doesn't find the move, but when I put it on the board, the winrate is 11% above KataGo's first choice. Also, :b89:

is +8% (KataGo just looks at the clamp instead), and :w90:

is +4%.

FWIW,

is Elf's top choice, with 31.6k rollouts, and for :w90:

it prefers the push through at D-11 with 61.5k rollouts, but only by 0.1%, i.e, not really at all. Since :w90:

gets only 3 rollouts, it inherits its winrate estimate from :b91:

, which is also Elf's top choice, with 21.7k rollouts. As mentioned before, :w98:

was not Elf's top choice, but it gets a winrate estimate 13½% better for White than the top choice. OC, with only 1 rollout, it inherits its winrate estimate from :b99:

, also Elf's top choice with 14.2k rollouts.

xela wrote:

With these apparent blind spots, I agree that we can't trust KataGo's evaluations of other moves round about this part of the game. In particular, I don't think we can conclude that :w94:

is actually a blunder.

Well, Elf thinks that :w94:

loses 36% to par. Even if we think that its evaluations hereabouts are off by 13% in favor of Black, and if we assume that all the winrate difference between :w94:

and its top choice is explained by that amount and so subtract 13% from 36%, we still get a loss of 23%, which is still a blunder in my book. (We cannot conclude that :b89:

and

and their evaluations are blindspots for Elf, given its number of rollouts.)

xela wrote:

In hindsight, after seeing :w98:

I wondered if :b85:

was a mistake. But any alternatives appear to be even worse.

Is there a way to promote :w98:

in Elf's searches?

xela · **#45**

I noticed that BQM265 is from an Otake game of the same period.

The book Relentless talks about some positions being "wide", in the sense of having lots of options. The BQM 265 position is very wide in this sense. In many variations, KataGo explores a lot of moves and is slow to settle on a clear-cut best play.

Click Here To Show Diagram Code: [go]$$Bc Suiuchi-Otake 1974-05-01, black to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O . . . | $$ | . X X X . X . . . . O . . O . . X . . | $$ | . X O O O . . . . , . . . . . X . . . | $$ | . O O . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . d . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . a , . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . . . b . . . c . . | $$ | . . . . O . . . . O . X . X . . . . . | $$ | . X X . . . . . . . . . . . . X . . . | $$ | . . . O . . . . . . . . . O . . . . . | $$ | . . X O . . . . . O . . . . . X X . . | $$ | . . X O . . . . . . . . . O . X O X . | $$ | . . . . . . . . . . . . . . . O O O . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

There are four "hot" areas of the board. On the left, can black invade at a, or can white get sente to defend there first? On the right, b, c, d and a few other places could be promising invasion points. At the top, normal play would look like this:

Click Here To Show Diagram Code: [go]$$Bc $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . b O . . . | $$ | . X X X . X . . . . O 2 6 O a . X . . | $$ | . X O O O . . . . , . 1 4 3 . X . . . | $$ | . O O . . . . . . . . . 5 . . . . . . | $$ | . . X . . . . . . . . . . . . X . . . |[/go]

But with the rest of the board looking so interesting, both players are keen to get sente, so white might tenuki after :b3:

, or even after :b1:

, and decide that allowing black a followed by b is a fair trade for something on the left or right side.

At the bottom, a hane by either player is big but gote. How does this compare with the rest of the board?

Click Here To Show Diagram Code: [go]$$Bc Black has first move at the bottom $$ | . . . . O . . . . O . X . X . . . . . | $$ | . X X . . . . . . . . . . . . X . . . | $$ | . . . O . . . . . . . . . O . . . . . | $$ | . . X O . . . . . O . . . . . X X . . | $$ | . . X O . . . . . . . . . O . X O X . | $$ | . . 3 1 2 a . . . . . . . . . O O O . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

If black gets there first, there is some aji at a

Click Here To Show Diagram Code: [go]$$Wc White plays first at the bottom $$ | . . 4 , . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 5 O . . . . . . . . . b . . c . . . | $$ | . . . . O . . . . O . X . X . . . . . | $$ | . X X . . . . . . . . . . . . X . . . | $$ | . . . O . . . . . . . . . O . . . . . | $$ | . . X O . . . . . O . . . . . X X . . | $$ | . . X O . . . . . . . . . O . X O X . | $$ | . 2 1 3 . . . . . . . . . . . O O O . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

After

, it's harder for black to invade at :b4:

because

threatens to kill the corner. But KataGo says that black shouldn't be afraid, and shows sequences where black leaves a bunch of dead stones behind (either in the corner or at :b4:

) and still manages to achieve whole-board balance.

Some variations for your entertainment:

And here's the full game, showing how people used to play sanrensei before the AI revolution!

xela · **#46**

By the way, an article in Go World 52 sheds some light on the difference between "5 points komi but White wins jigo" and 5.5 points komi. On page 47, Sakata relates how Fujisawa Shuko won the first (modern era) Meijin title in 1961. In the last round, Sakata played black against Go Seigen and finished 5 points ahead on the board, meaning that the position was jigo, a win for Go Seigen. So at the end of the round robin, both Go Seigen and Fujisawa had 9 wins and 3 losses. Without jigo, this would have resulted in a playoff. But Go Seigen's "jigo-win" didn't count as much as a "real" win, so the title was awarded to Fujisawa without a playoff.

lightvector · **#47**

I don't know how well it actually works in reality, but in theory you can make KataGo treat a draw as favorable but as only a fraction of a win. You have to actually pick a numeric value though. So for example drawEquivalentWinsForWhite = 0.75 instead of the default drawEquivalentWinsForWhite = 0.5 would make it consider a draw to be like 3/4 of a win and 1/4 of a loss for white.

Reviewing a 1971 Otake game with Kata

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