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Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 9:08 am
by topazg
Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 9:24 am
by Bill Spight
Bill Spight wrote:Here is what I get for the interesting position in emeraldemon's game:
$$Wc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X . |
$$ | . . . , . . O X . , . . . . . X X O . |
$$ | . . . O . O X . . X . . X X X O O O . |
$$ | . . . . O . X . . . 2 X O O O . . . . |
$$ | . . . . . . . . . . . 1 . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X . |
$$ | . . . , . . O X . , . . . . . X X O . |
$$ | . . . O . O X . . X . . X X X O O O . |
$$ | . . . . O . X . . . 2 X O O O . . . . |
$$ | . . . . . . . . . . . 1 . . . . . . . |
$$ ---------------------------------------[/go]
is a 4 1/6 point sente.
Oops! I goofed.
$$Wc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X . |
$$ | . . . , . . O X . , . . . . . X X O . |
$$ | . . . O . O X . . X . . X X X O O O . |
$$ | . . . . O . X . . 8 4 X O O O . . . . |
$$ | . . . . . . . . 6 5 3 1 2 7 . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X . |
$$ | . . . , . . O X . , . . . . . X X O . |
$$ | . . . O . O X . . X . . X X X O O O . |
$$ | . . . . O . X . . 8 4 X O O O . . . . |
$$ | . . . . . . . . 6 5 3 1 2 7 . . . . . |
$$ ---------------------------------------[/go]
Black should throw in at
. After
the next play gains 1/3 (Black will capture the three White stones in the process).
So the sente is worth only 3 2/3 points.
Edit: I see that there are additional complications, but I have to run now.
OK, I'm back.
Well, I goofed all right, but not in the way that I thought.
$$Wc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X . |
$$ | . . . , . . O X . , . . . . . X X O . |
$$ | . . . O . O X . . X . 5 X X X O O O . |
$$ | . . . . O . X . . . 3 X O O O . . . . |
$$ | . . . . . . . . . . 4 1 2 . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X . |
$$ | . . . , . . O X . , . . . . . X X O . |
$$ | . . . O . O X . . X . 5 X X X O O O . |
$$ | . . . . O . X . . . 3 X O O O . . . . |
$$ | . . . . . . . . . . 4 1 2 . . . . . . |
$$ ---------------------------------------[/go]
On the assumption that I originally made, Black cannot stand this ko (which also arises if Black plays
at
). So I got the right answer the first time.
Let this be a lesson to me.
Just because you get the right answer doesn't mean you're right. Be thorough.
Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 5:28 pm
by ndkrempel
You didn't show the variations when black plays first and white tenukis. Can't black go on to capture 3 stones in gote by exploiting the life&death issue of the corner? Doesn't that make it more than 4 1/6 points sente?
Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 5:32 pm
by ndkrempel
Ok, on reflection I don't think black can capture any stones, but seems like black can gain a couple of extra points beyond the obvious ones, so still worth looking into the variations when black plays first and white tenukis.
Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 5:42 pm
by ndkrempel
Ok, apologies for the multiple posts, but thought I should put some substance to my comments. Here is the best I can see for black playing first:
$$Bc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X 9 |
$$ | . . . , . . O X . , . . . . . X X O 7 |
$$ | . . . O . O X . . X . . X X X O O O 8 |
$$ | . . . . O . X . . . . X O O O . 6 . . |
$$ | . . . . . . . . . . . 5 1 3 4 . . 0 . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X 9 |
$$ | . . . , . . O X . , . . . . . X X O 7 |
$$ | . . . O . O X . . X . . X X X O O O 8 |
$$ | . . . . O . X . . . . X O O O . 6 . . |
$$ | . . . . . . . . . . . 5 1 3 4 . . 0 . |
$$ ---------------------------------------[/go]
(The final move is to avoid a seki.)
Note that black got the 7 move in sente here, which he doesn't get in most variations where white has played 5 first.
Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 7:36 pm
by Dusk Eagle
Impressive analysis Bill
. One question:
$$W
$$ --------------------
$$ . . . X 1 X X O . .
$$ . . X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O
- Click Here To Show Diagram Code
[go]$$W
$$ --------------------
$$ . . . X 1 X X O . .
$$ . . X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O[/go]
Black doesn't actually have to respond to this move, as white is not actually threatening to capture the four black stones. However, white can then fill in in sente:
$$W
$$ --------------------
$$ . . . X O 3 . O . .
$$ . 4 X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O
- Click Here To Show Diagram Code
[go]$$W
$$ --------------------
$$ . . . X O 3 . O . .
$$ . 4 X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O[/go]
This result is -3. So, if black were to play like this, white would have gained -3/2 points with each move. Since this is worse than the result you showed for black, black should have captured
rather than let white protect it in sente. Is my analysis correct?
Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 11:02 pm
by Bill Spight
Dusk Eagle wrote:Impressive analysis Bill
. One question:
$$W
$$ --------------------
$$ . . . X 1 X X O . .
$$ . . X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O
- Click Here To Show Diagram Code
[go]$$W
$$ --------------------
$$ . . . X 1 X X O . .
$$ . . X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O[/go]
Black doesn't actually have to respond to this move, as white is not actually threatening to capture the four black stones. However, white can then fill in in sente:
$$W
$$ --------------------
$$ . . . X O 3 . O . .
$$ . 4 X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O
- Click Here To Show Diagram Code
[go]$$W
$$ --------------------
$$ . . . X O 3 . O . .
$$ . 4 X X X O O O . .
$$ X X O O O O . . . .
$$ . . . . . , O O O O[/go]
This result is -3. So, if black were to play like this, white would have gained -3/2 points with each move. Since this is worse than the result you showed for black, black should have captured
rather than let white protect it in sente. Is my analysis correct?
The sequence -- White takes two stones, Black takes back, White plays atari, Black connects on the second line, White takes ko --, should be considered as a unit (except for ko threats). This happens frequently, the hane-connect is a common example. I do not know of a go term for this, but the CGT term is reversal. Yes, considered as individual plays the capture and recapture each gain 1 2/3 points, but that just takes us back to where we began, in terms of points.
So you are right, Black should take back.
Re: Frequent Yose Position - Which is the Better Move?
Posted: Thu Nov 04, 2010 11:20 pm
by Bill Spight
ndkrempel wrote:Ok, on reflection I don't think black can capture any stones, but seems like black can gain a couple of extra points beyond the obvious ones, so still worth looking into the variations when black plays first and white tenukis.
Yes, I think you are right, I wasn't very thorough. {sigh}
Re: Frequent Yose Position - Which is the Better Move?
Posted: Sun Nov 07, 2010 11:43 am
by Bill Spight
ndkrempel wrote:Ok, apologies for the multiple posts, but thought I should put some substance to my comments. Here is the best I can see for black playing first:
$$Bc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X 9 |
$$ | . . . , . . O X . , . . . . . X X O 7 |
$$ | . . . O . O X . . X . . X X X O O O 8 |
$$ | . . . . O . X . . . . X O O O . 6 . . |
$$ | . . . . . . . . . . . 5 1 3 4 . . 0 . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bc
$$ | . . . . . . . O X . . . . . . . . . . |
$$ | . . . . . . O X . . . . . . . . X . . |
$$ | . . O . . . O X . . . . . . . . . X 9 |
$$ | . . . , . . O X . , . . . . . X X O 7 |
$$ | . . . O . O X . . X . . X X X O O O 8 |
$$ | . . . . O . X . . . . X O O O . 6 . . |
$$ | . . . . . . . . . . . 5 1 3 4 . . 0 . |
$$ ---------------------------------------[/go]
(The final move is to avoid a seki.)
Note that black got the 7 move in sente here, which he doesn't get in most variations where white has played 5 first.
Many thanks.
OK, let's try again. Here I assume AGA territory scoring, which is equivalent to Chinese scoring. (I also include notes on Japanese scoring.) The difference lies in the value of the seki. By AGA scoring White gets two points in the seki and Black gets one point. By Japanese scoring seki is worth 0.
(;ST[2]AP[GOWrite:2.2.21]CA[ISO8859-1]FF[4]GM[1]SZ[19]AB[lr][im][ro][hp][qn][pp][qp][hn][jq][nq][mq][oq][gr][ho][gq]PB[ ]PC[http\://lifein19x19.com/]PL[B]PW[ ]PM[0]GN[ ]AW[mr][or][nr][gp][hm][rp][qq][rq][pq][dq][co][fq][gn][go][er]DT[2010-11-06]C[
]FG[259:]
(
;B[ms]C[This reverse sente gains 5.75 points. {6 by Japanese rules.}]
(
;W[ns]
;B[ls]
;W[ps]C[This sequence gains 2.75 points. {3 points by japanese rules. The sequence is ambiguous between sente and gote.}]
(
;B[sp]
;W[sq]
;B[so]C[This sequence gains 1 point.]
)
(
;W[so]
;B[sn]
;W[sp]C[This sequence gains 1 point.]
)
)
(
;B[ns]
;W[os]
;B[ls]
;W[qr]
;B[sp]C[This sequence gains 2.75 points. {By Japanese rules protecting the corner gains 3 pointns, so White keeps playing.}]
(
;W[sq]
;B[so]
;W[rs]C[This sequence gains 2.5 points. {By Japanese rules the long sequence is like a Black sente -- it is ambiguous between sente and gote -- and the local count remains thesame.}]
)
(
;B[rs]
;W[qs]
;B[sr]
;W[sq]
;B[so]C[This sequence gains 2.5 points. {3 points by Japanese scoring.}]
)
)
)
(
;W[ls]C[White sente.]
;B[kr]
(
;W[ms]C[This gote gains 2 points.]
(
;B[sp]
;W[sq]
;B[so]
;W[ks]
;B[js]C[This sequence gains 1 point.]
)
(
;W[ks]
;B[js]
;W[so]
;B[sn]
;W[sp]C[This sequence gains 1 point.]
)
)
(
;B[ms]C[This gote gains 2 points.
Black has sente.]
(
;W[ns]C[The reverse sente gains 1 2/3 points.]
(
;B[sp]
;W[sq]
;B[so]C[This seouence gains 1 point.]
(
;W[ps]
;B[ks]
;W[ms]C[This sequence gains 1/3 point.]
)
(
;B[ps]
;W[qr]
;B[ks]
;W[qs]
;B[ms]C[This sequence, of course, gains 1/3 point.]
;W[tt]
;B[ls]
)
)
(
;W[so]
;B[sn]
;W[sp]C[This sequence gains 1 point.]
(
;B[ps]
;W[qr]
;B[ks]
;W[qs]
;B[ms]C[This sequence gains 1/3 point.]
;W[tt]
;B[ls]
)
(
;W[ps]
;B[ks]
;W[ms]C[This sequence gains 1/3 point.]
)
)
)
(
;B[ks]
;W[sp]C[Surprise!
White has sente.
]
(
;B[so]C[The reverse sente gains 1 point.
Now the remaining play in the corner can wait until the end of play, or until the next ko fight.]
(
;W[qr]
;B[ns]
;W[os]
;B[ls]
)
(
;B[ns]
;W[os]
;B[ls]
;W[qr]
)
)
(
;W[so]
;B[sn]C[The remaining corner play can wait until the end of play, or until the next ko fight.]
(
;W[qr]
;B[ns]
;W[os]
;B[ls]
)
(
;B[ns]
;W[os]
;B[ls]
;W[qr]
)
)
)
)
)
)
There are some cute plays in there, I think.
Edit:
Hmmm. Where does that "Black to play" come from?
(or a White play at 1) gains 1 5/6 points.
