Author: Odd Gunnar Malin
Date: 14:12:12 04/25/02
Go up one level in this thread
On April 25, 2002 at 15:27:26, Robert Hyatt wrote:
>On April 25, 2002 at 13:49:42, Dann Corbit wrote:
>
>>On April 25, 2002 at 13:26:43, Robert Hyatt wrote:
>>
>>>On April 25, 2002 at 12:39:36, J. Wesley Cleveland wrote:
>>>
>>>>On April 25, 2002 at 02:54:03, Andreas Herrmann wrote:
>>>>
>>>>>Hi,
>>>>>
>>>>>I want to implement double nullmove in my chess engine again. Now i'm searching
>>>>>for Zugzwang postions, which should be solved by double nullmove instead of
>>>>>normal nullmove.
>>>>>Another question: How much time costs the double null move in the average.
>>>>>I have tested it in some positions, and my engine needs about 30 to 40 percent
>>>>>more time for the same search depth. Is that normal or is that to much.
>>>>
>>>>That seems like far too much. Are you reducing the search depth again for the
>>>>second nullmove and only doing it when the first nullmove causes a cutoff? You
>>>>might also not want to do it too near the leafs, i.e. if the first nullmove goes
>>>>directly into your quiescence search.
>>>
>>>
>>>One simple test... determine how often, in normal positions, the _second_ null-
>>>move search fails high. Whenever it does, the the first null-move search fails
>>>low and is useless. that is probably where the cost is being exposed...
>>>
>>>In zug positions, the second fail high will cause the first to fail low, which
>>>prevents zug problems. But if it also causes a large number of normal positions
>>>to fail this test as well, then it is losing part of the advantage of null-move
>>>in general...
>>
>>I had a notion about double null move --
>>
>>Implement double null move in the place where normally you will just turn null
>>move off [except for check]. Use your regular null move algorithm as always,
>>but when conditions indicate null move is not a good idea, switch to double null
>>move.
>
>
>If it was easy to identify positions where a null-move might cause problems,
>the problem would already be solved.
>
>:)
I think he thinking about:
if (!incheck && !whatever)
{
if (material > allow_nullmove)
{
ordinary nullmove
}else
{
double nullmove
}
}
I don't know if the better engines do it like, but I think many engines have a
test on material.
This was my first thought too when I saw the arguments.
Odd Gunnar
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