Author: Uri Blass
Date: 22:30:00 04/17/02
Go up one level in this thread
On April 17, 2002 at 20:20:04, Dann Corbit wrote:
>On April 17, 2002 at 20:05:52, Ricardo Gibert wrote:
>
>>The title of the thread is Null move *generaliztion*. Are there positions that
>>Null move *cannot* solve? Yes. Now the question is, "Under what conditions?"
>>There is no question that a null moving program with modification can
>>theoretically still solve any position. That's not the issue.
>
>I still don't understand how null move (properly implemented) can *ever* cause a
>search to simply fail. After all, the *only* side effect is that it reduces
>search depth by some number of plies (as defined by R).
>
>If we are searching illegal moves, or if we recursively apply null move without
>limit {and surely this is a very bad bug} then all sorts of strange things can
>happen.
>
>But if:
>1. We only search legal moves
>2. We do not reduce depth infinitely but only finitely
>Then my question is:
>"How can the search fail forever?"
Null move can fail forever.
It is a known problem.
some programs can never solve mate in 2 when a zunzwang is involved and the side
to move has another option to draw.
The reason is simple:
1)They find a drawing move.
2)They search the right move and see that it threats nothing that is more than a
draw so they prune it.
The example that was posted may not a good example and it is better to post a
mate in 2 that programs fail to solve.
Uri
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