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Endgame Test One - Solution
  Difficulty: Dan level   Keywords: EndGame, Problem

Solution for "The Practical Endgame Test One"
See also Endgame Test One Solution 2 and Endgame Test One Solution 3.


[Diagram]
White wins by 1 point

Black 1 is sente against the bottom white group, so White has to answer at 2. Next Black cuts at 3 and reduces White even more.

Black has sente to play the big point of 9 and White gets 10 next.


[Diagram]
White wins by 1 point (continued)

Black continues with 1 and White gets the last point with 6. Then 8 and 9 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:

[Diagram]
White wins by 3 points

White plays 1 here instead of 10 in the previous diagram (at 2 here). So Black plays 2 - I actually thought of this line, but somehow dismissed it, because 2 is bigger than 1. I didn't take the sente/gote relationship into account. After Black 10 the sequence continues with a through d. Now White wins by 3 points. --ArnoHollosi


[Diagram]
White wins by a large margin

And if instead of 3 above White plays this? 6 connects? -- HolIgor


[Diagram]
White wins by 4 points

OK, so then Black 2 here. If White answers at 3 and 5 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 6 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.


[Diagram]
Another try: White wins by 3 points

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.



Solution

[Diagram]
The Answer Part 1

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


[Diagram]
Part 2 - W+4

The key point is White 2 here. Black can't win the ko and would be forced to connect at a (allowing b) if he played away at 6 instead of connecting at 3. So White gets to come back for 4 and 6.



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 Black 3 (in the above diagram) look at EndGameTestOneSolution2. (proving that this may not be a "good" problem)

Dave: for a more in depth analysis of another position that arose see EndGameTestOneSolution3.

Arno: new problem - alternative to Black 1 (in the last diagram). See EndGameTestOneSolution4



This is a copy of the living page "Endgame Test One - Solution" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.