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Subject: Question: WAC.001 and null move

Author: Artem Pyatakov

Date: 23:37:55 08/19/01


I have a (somewhat) strange question about null move and WAC.001.

Here is what happens when I run my program:
Depth=4 (Correct PV here) +MATE2
Depth=5 Fail Low !!! (Aspiration window +MATE2-50 +MATE2+50)
Depth=5 +MATE2

I investigated and discovered why this strange fail low happens: it happens
because when I start search search on depth 5, I search the move in the PV from
depth 4 (the correct mating move) first. After making the move, I do a null move
search (R=2) - and this is where it returns beta.

So, I have two questions:
1) Is this behavior inherent to null-move or is there a way around it?
2) How would I avoid this kind of fail-low behavior?  (Perhaps, I should write
different code for null move when a search returns -MATE/+MATE?)

Thank you

Artem



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