InvincibleTheGamesOfShusaku/Game 25 analyzed with KataGo

This was the first castle game review with KataGo. Later I repeated the exercise and it grew into a series -- Dieter

Out of curiosity I took a random game from Invincible and analyzed it using KataGo. I did expect KataGo to give nuances to the professional commentary used in the book, but I didn't expect the result. Basically, the claims made in the book do not correlate at all with the AI analysis. What the commentary calles "losing moves" by Shusaku's opponent Sakaguchi Sentoku are blue moves or losing a fraction of a point, while some of Shusaku's moves that are being glanced over are losing 3 points. By move 80 the game is hopeless for White, according to the commentary, while KataGo assesses the position as White losing by 5 points, which is an improvement to the start of the no komi game, which KataGo assesses as a 7 point disadvantage.

The book commentary is by Sanno Hirotaka.

Moves 1 to 10  

The game starts off with a taisha joseki in the lower left.

Moves 11 to 20  

B19 here requires a favorable ladder for Black. I'm leaving out the diagram given in the book to prove this. KataGo thinks this is a 3 point mistake and should have been at A. Prior to that, W18 was a 2 point mistake and should have been at A as well. The book doesn't mention A as a vital point for both.

The book does label W20 as a non-joseki move which costs White. KataGo disagrees and finds only a fractional loss, compared to the book's suggested joseki move B.

Moves 21 to 30  

KataGo thinks W2 is a small mistake (1 point) and should be a hanging connection instead. The hane at the head of two with B23 is too good.

The book then explains why W26 is better than the usual hane:

Diagram 3 in the book  

The book states: "This would be the usual way to make shape but that would give Black an ideal peep at A". KataGo is not considering A and when I played it out, it assesses the peep as a 2 point loss for Black. My interpretation is that Black's peep doesn't really gain anything, since White confirms the eye and the combination of Black's keimas is thin.

Moves 21 to 30  

Back to the game, where White's subsequent move at W28 which "invites a forceful attack by Black. It's an over-extension which becomes the losing move", says the book and it proceeds with an eulogy on Shusaku's ability to punish opponent overplays.

KataGo thinks W28 is the best possible move. The difference with the book's suggestion for White to refrain with a simple one space jump at B29, is small but nonetheless positive, even after many playouts. Yes, Black can counterattack but KataGo doesn't consider that to be a big problem. On the contrary, it prefers B39 to take it easy with B, after forcing with A. This time A is a good forcing move:

Forcing - 1  

If White answers at W2 here, Black can later grab two stones with A.

Forcing - 2  

If W2 here, White has bad aji around A.

Moves 31 to 40  

The cross cut and its subsequent moves W32-W36 are all normal according to KataGo. The book doesn't explain why B37 holds back to a solid extension but KataGo thinks this is a rather big mistake. A one space jump towards A would keep the advantage around 4 points, while now White can move faster, towards B, and the difference shrinks to 2 points.

KataGo also doesn't like B35 all that much, my interpretation being that it strenghtens White unnecessarily and destroying the shape is not that valuable.

The book calls W38 unnecessary and KataGo thinks it's a 2 point mistake, my interpretation being that it reduces a liberty.

Moves 41 to 50  

After W40 in the previous figure, B41 probably shows why B37 was so bad, as it loses tempo.

The book says "B35 is the kind of shape professionals dream about. It leads out Black's sole weak group while amply maintaining the pressure on White's two weak groups. Black seems to be heading for a comfortable win" and puts the blame again on White's losing move at W28. KataGo sticks with an evaluation of B+3 which is not to blame on W28 (a blue move) but on Black's first move advantage which he has already half squandered.

On W48 the book says: "... is the instinctive fighting move but here it is welcomed by the opponent". KataGo seems to agree on the following diagram being better:

Diagram 9 in the book  

In fact this would reduce the gap to below 2 points, far from the comfortable lead the commentary suggests.

Moves 51 to 60  

While the book glances over it, KataGo finds W52 at fault and suggests cutting on the other side. This is interesting:

Sacrifice - 1  

Sacrificing two stones like this, sets up a squeeze. After W11 at A, White can capture the original cutting stones or extend at the side. The interesting question is: what if Black avoids the squeeze?

Sacrifice - 2  

KataGo evaluates this as a profitable swap for White. I can't read the pro commentary's mind but I assume it would evaluate the loss of the center stones as unbearable for White.

Moves 51 to 60  

Back to the game: the book calls W56 "the losing move if that wasn't already claimed before". KataGo doesn't think about W56 but, when played, doesn't consider it that bad. Next the book criticizes W60 as it seems to attack Black's shape but does so in vain. KataGo doesn't think it's worse than the book's suggestion to defend the top at A instead.

Moves 61 to 70  

The book calls W64 logical but hails Shusaku's flexibility to drop the pivotal stones and make good shape at B65. "The game is over".

KataGo seems to agree B65 maintains the lead in a simple way but not distinctively better than connecting at A, Black's lead being 4,5 points in both cases. Such a lead in the late middle game is game over indeed at the pro level but it's still a reduction from the initial advantage.

The book calls B67 a declaration of victory: Shusaku is allegedly so far ahead that he can afford soft moves like this one. KataGo agrees it is soft and a White cut & connect at A would reduce Black's lead to 2,5 points.

As for W70, this is a "dubious move" in the book. KataGo thinks it's the best move after cutting and connecting in the center again.

Moves 71 to 80  

So, when Black connects at B71, the game - in my opinion - is simplified. By W80 the game is still a 5-pointer for Black and we're approaching the end game.

In conclusion, the commentary in the book, as said, hardly correlates with KataGo's analysis. While such analysis requires much more time and playouts, force feeding the game moves and the variations, the times when I did so did not reveal a sudden shift in KataGo's evaluation towards the commentary's. Vice versa we can't retrospectively find out what the commentator(s) would say to KataGo's main issues with the game.

With this comparison, I don't want to devaluate the commentary, let alone the great book, but rather point out that commentaries like these might reflect biases with the commentator at the time and must be taken with the necessary caution - just like KataGo's evaluations.

InvincibleTheGamesOfShusaku/Game 25 analyzed with KataGo last edited by Dieter on December 4, 2023 - 17:47
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