Re: computer-go: Go4++: Passing in tsume searches.

[Thomas Wolf <twolf@xxxxxxxxxxxxxxxxxxx>]

>Are there any tsume problems where the defender *must* pass *more than 
>once* (not necessarily consecutively) in order to prove it's alive or 
>seki?
>
>Are there any tsume problems where the defender *must* pass but the pass 
>move is not the defenders last move before the search terminates?

Look at the following problem:

 6 * * * . . . . .
 5 o o * * * . . .
 4 . o o o * * . .
 3 o * o o * * . .
 2 * * . o * * . .
 1 . o o o * * . .
   A B C D E F G H

Assume o has just captured * on A4 and * is to move next.
The optimal play has lots of passes:

* passes,    o passes,
* A4,        o passes, 
* C2,        o A3, 
* ko-threat, o ko-answer, 
* A4,        o passes, 
* A1

By adding outside liberties for o one can increase the number of
passes of o arbitrarily (and by that increase the number of necessary
ko-threats if more than 3 outside liberties for o are added).

Thomas