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Notchers
BeginnerExercise3...
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One-Space Notchers
    Keywords: Life & Death

One-space notchers are groups that consist of a chain on the second line, interrupted by a notch of one empty space on the second line and one stone on the third. The term was invented by James Davies. See also Notchers, Two-Space Notchers and Three-Space Notchers.

The rule for one space notchers is: "Four die, Seven live". You may also remember this as: "Five and Six are unsettled".

[Diagram]
Four die

Here's the proof that "Four die". Even if Black plays first, White always has an answer to keep his group dead. Black 1 is answered by White 2 and vice versa.


[Diagram]
Seven live

Here's proof that "Seven live". Even if White plays first, Black always has an answer to keep his group alive. The diagram shows one white attack that fails. You can verify for yourself that it doesn't matter where the notch is located. You can also verify that five- and six-space notchers are unsettled, i.e. that the black group is alive if Black plays first and dead if White plays first. If you don't know how to verify unsettled cases, look in the discussion of two space notchers.


Classification

[Diagram]
One-space notchers

Marked points: possible weaknesses
Marked stones: legs



Classification

See notchers for the coding.

  • All of 111xx, 112xx are dead and not worth discussing
  • All of 1xxWW are dead until 133WW. 133WW can make a ko. From 134WW onward it can live by connecting the stone in atari:

[Diagram]
134WW

Black lives with 1



122

[Diagram]
122WN

dead


[Diagram]
122WS

can live with 1


[Diagram]
122NN

can live with 1


[Diagram]
122NS

can live with 1


[Diagram]
122SS

can live with 1



All 122 can live, except 122WW and 122WN which are dead


123

[Diagram]
123WN

Black can make a ko



[Diagram]
123NW

Black can make a ko


[Diagram]
123WS

Black can live


[Diagram]
123NN

Black can live



(...)

[Diagram]
123SS

Black can live. White can kill at 1.



All 123 can live, except for 123WW, dead, and, 123WN and 123NW, where Black can make a ko.


133

[Diagram]
133WN

Black can live at 1 or A.


[Diagram]
133WS

Black lives. White 1 is the strongest move. Any other move is answered by Black 1.


[Diagram]
133NN

Black lives. White 1 is the strongest move. Any other move is answered by Black 1.



(...)

133WW makes ko. 133WN can make life. All other 133xx live


Table

See notchers for the coding.

 111WW D - 112WW D - 113WW D -- 114WW D -- 115WW D -- 116WW LD
111WN D - 112WN D - 113WN D -- 114WN D -- 115WN LD - 116WD LK
111WS D - 112WS D - 113WS LD - 114WS LD - 115WS LK - 116WS LK
111NN D - 112NW D - 113NW D -- 114NW D -- 115NW LD - 116NW LD
111NS D - 112NN D - 113NN LD - 114NN LD - 115NN L -- 116NN L
111SS D - 112NS D - 113NS LD - 114NS LD - 115NS L -- 116NS L
xxxxx --- 112SW D - 113SW LD - 114SW LD - 115SW LD - 116SW LD
xxxxx --- 112SN D - 113SN LD - 114SN LD - 115SN L -- 116SN L
xxxxx --- 112SS D - 113SS LD - 114SS LD - 115SS L -- 116SS L
 122WW D -- 123WW D -- 124WW D -- 125WW LD   
122WN D -- 123WN KD - 124WN LD - 125WN ?
122WS LD - 123WS LD - 124WS L -- 125WS ?
122NN LD - 123NW KD - 124NW LD - 125NW ?
122NS LD - 123NN LD - 124NN L -- 125NN ?
122SS LD - 123NS LD - 124NS L -- 125NS ?
xxxxxx --- 123SW LD - 124SW L -- 125SW ?
xxxxxx --- 123SN LD - 124SN L -- 125SN ?
xxxxxx --- 123SS LD - 124SS L -- 125SS ?
 133WW KD - 134WW LD
133WN LD - 134WN ?
133WS L -- 134WS ?
133NN L -- 134NW ?
133NS L -- 134NN ?
133SS L -- 134NS ?
xxxxxx --- 134SW ?
xxxxxx --- 134SN ?
xxxxxx --- 134SS ?

(Work in progress)

Authors: BillSpight, DieterVerhofstadt



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