Practical Endgame Test 1 / Solution

Solution for "Practical Endgame Test 1"
See also /Solution 2 and /Solution 3.

is sente against the bottom white group, so White has to answer at . Next Black cuts at and reduces White even more.

Black has sente to play the big point of and White gets W10 next.

Black continues with and White gets the last point with . Then and are necessary defensive moves, once all the dame are filled in.

Count:

White has 4 points at the bottom (3+1 capture) 12 points at the top (11+1 prisoner)

Black has 5 points on the left (4+1 capture) 10 points on the right (9+1 prisoner)

White wins by 1

--ArnoHollosi

DaveSigaty: White has not played as well as she could.

OK, actually, this seems better for White:

White plays here instead of W10 in the previous diagram (at here). So Black plays - I actually thought of this line, but somehow dismissed it, because is bigger than . I didn't take the sente/gote relationship into account. After B10 the sequence continues with a through d. Now White wins by 3 points. --ArnoHollosi

And if instead of above White plays this? connects? -- HolIgor

OK, so then Black here. If White answers at and she wins by 3 points. Hmm, wait - White can play at a now and force Black to answer at b; then she plays c. Black cannot start the ko capturing with c, because Black could not resist White d after White b. So White wins by 4 points. --ArnoHollosi

DaveSigaty: Most of the right ideas are coming out but there are more resources in this position than have shown up yet. Hint: the correct result is White wins by 4 points. But we haven't yet seen the correct order. For example, in the last diagram above Black's play at is not the best and Black lets White get at least one more point than she should (I think!).

By the way, this problem looked fairly uncomplicated when I looked at it except for the tesuji in the lower left corner. However, in checking the solution I found that in the original readers' poll in Kido only 6% of the answers sent in were correct.

Arno: I asked my high dan friend about this problem, and he came up with this new sequence on the right, which gives White sente. However, whichever variation we tried, White only wins by 3 points. I'm at my wits' end. Enlighten me please.

[edit]

Solution

Dave Sigaty: This is the big stuff that Arno got right from the beginning...

The key point is here. Black can't win the ko and would be forced to connect at a (allowing b) if he played away at instead of connecting at . So White gets to come back for and .

Dave: these problems should really have only a single line of correct play if they are good. In other words other choices by either Black or White should lead to worse results for Black or White respectively.

Arno: for alternatives to (in the above diagram) look at /Solution 2. (proving that this may not be a "good" problem)

Dave: for a more in depth analysis of another position that arose see /Solution 3.

Arno: new problem - alternative to (in the last diagram). See /Solution 4

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Practical Endgame Test 1 / Solution last edited by 116.232.160.247 on September 26, 2012 - 17:45

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