BQM 348

    Keywords: EndGame, Question

golearner -- Here's the end of a close game. Playing as White, I lost by 1.5 points! (In other words, at the final count, Black won this game by 1.5 points.) I wonder if I made the right plays, in the right order, or if I need to look earlier... (Actually, I suspect I do - I would have lost by a couple more points if Black hadn't filled in some territory unnecessarily.) Captures prior to this point: Black = 4, White = 12. Based on comments so far, I've tried to evaluate the starting position - that's at the end of this page. (I'm sure I've made some mistakes in values though...)

Moves 231 to 240  

Harleqin: I think that B5 loses a point, because now the point above W8 is sente for White.

Moves 241 to 250  

LukeNine45: I think W8 should be at B9 if you're taking gote in the corner there anyway.

golearner: Yeah, I'm not sure there was any value to playing there - I thought that during the game right after doing it...

Harleqin: B3 is unnecessary, losing a point in gote. Black should first play sente at 257, then 2 points gote at 256. W8 is minus half a point in gote. Note that Black could only play B9 here anyway, but now he gets it in sente. Instead, White should play 2 points gote at the left side (where move 253 went).

unkx80: Locally, W8 should be played at White a, Black b, White at B9. I don't think Black dares to play at c because White d will turn it into a ko. Because after my sequence, Black must connect at d anyway, I will assess the loss of the actual W8 to be 2 points.

Moves 251 to 260  

Harleqin: B3 loses a point, should first exchange B7 for W8, then hane and connect. The rest are neutral points.

Moves 261 to 270 (6: pass) (7: pass) (9: pass)  

Harleqin: B3 and B5 are unnecessary, losing a point each. If you were playing by area scoring, then each pass loses a point for black, too.

Moves 271 to 280 (1: pass) (7: pass) (9: pass) (10: pass)  

Moves 231 to 240  

Dave: I think the first question is whether B1 is sente. If White plays away (e.g. W4), what happens after B5 - B7?


golearner I've calculated the following - let me know how far off I am!

Black:               White:
AREA 1 (top line) - double gote
A, B, C              C, V, W, X, A
B+3                   W+1
Area worth 4/2 = 2
AREA 2 (left side) -double gote
D, E, F               F, Y, D
B+1                   W+1
Area worth 2/2 = 1
AREA 3 (bottom left) - two parts, first sente, second gote
Part 1 - sente:
G,H                       H,G
Area worth 0 points.
Z                           Z,b,a,d,c
0                           W+1
Area worth 1/2.
AREA 4 (line F) - sente/gote
I,J                         I
0                           W+1
Area worth 1/2?  How do you calculate the value when it's sente/gote?
AREA 5 (line L) - Same situation as AREA 4.
AREA 6 (line 6) - sente/gote
M,N                          N
Value = 0
AREA 7 (right edge) - gote/sente
O, P, Q, R, S             Q, e, O, S
B+1                           0
Value = 1/2?

Harleqin: As far as I can see, Area 1 is double sente (see Dave's contribution above). Also, after white C, black V, Black has W as sente, while it is gote for White, so you can assume W is Black's privilege. In your terms:

Black:               White:
AREA 1 (top line) - double sente
A, B, C, protect     C, V, later Black has W, A
B+2                   W+2
Area worth 4.

golearner: Okay, I think I see that. (I hadn't realized the trouble Dave's idea causes White in the corner.) It looks like area 1 is the hottest area.

Dieter: there is also another point in area 2, so 3 pts double gote, and one more point in 3

golearner: I'm not sure how you're getting the extra points there, unless it's area vs. territory scoring.

Harleqin: Nothing like that. It is just that, if White gets this endgame, Black has to protect again when the outside liberties are filled.


Bill: a is technically White's sente, since it threatens Black's huge group. I think it is worth 9 7/9 points, but I'm not exactly sure. The main thing, as Dave and Harleqin show, is that at this point it is double sente.

b is a gote that gains 1 1/2 points. If White plays there Black will have to fill at z later, as Dieter points out.

Everything else is worth 1 point. c, d, and e are Black sente; f is ambiguous, sort of like White sente; g is a gote that gains 1 point (As unkx80 points out, if Wg Black must later protect around y.).

Suggested play  

Bill: First, Black takes the double sente, and then takes his sente.

Dave: Bill, is B7 sente in this situation? Is it possible for White to pick up a point by playing at a? White is 3 points better for having played a, but B8 and d in sente give Black 2 points back. I am thinking of b and c as miai, but I am not sure whether I am correct overall.

Bill: White only gains 1 1/2 points by a gote at a, but gains 2 points by a reverse sente at W8. However, because of tedomari, I don't think it affects the result. See the alternate play diagrams below.

Suggested play (continued)  

Bill: Next, Black gains 1 1/2 points with B1 - B3. W4 threatens B5, a 2 point sente. Black does not respond to W6, but plays B7 to get the last play with B9. I think that puts Black 10 points ahead on the board.

Alternate play  

Bill: White may ignore B1 to take the largest gote with W2 - W4. Then Black takes his sente.

Alternate play (continued)  

Bill: Although technically the gote, W2 in the previous diagram, which gains only 1 1/2 points, is smaller than the reverse sente at B5, which would have gained 2 points, White gets the 1/2 point back because Black gains only 1 point with B3 in this diagram. The end result is the same as the suggested play. By comparison White gains 3 points on the left side but loses 2 points in the center and 1 point on the right side. (The swing points are marked.)

Bill: Your last mistake was 248, which loses 1 point in gote. W246 should have been at 253, but that is unlikely to win. As it was, you gained 8 points against par in this endgame! Thank your lucky stars for that.

Saving the corner  

W4 elsewhere

Bill: Earlier I said that White's atari at B3 was sente. That means that B1 - B3 is gote. Here is a little about responding to B5.

(At this point in the game W4 should be at B5, OC.) But in this situation I think that W6 is the right response to B5, to avoid worse. (See Dave's diagram.) Earlier in the game the next diagram is normally correct, I think.

Orthodox play  

W8 elsewhere.

Bill: This is the sequence I used to calculate the size of the play. It ends in gote with B7. (Later B9 - W10 is sente.)

BQM 348 last edited by PJTraill on February 10, 2019 - 17:47
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