# Computer Chess Club Archives

## Messages

### Subject: Re: Null-Move: Difference between R = 2 and R = 3 in action

Author: Omid David

Date: 18:31:14 07/13/02

Go up one level in this thread

```On July 13, 2002 at 11:57:00, Vincent Diepeveen wrote:

>On July 13, 2002 at 11:17:12, Omid David wrote:
>
>For diep the adaptive nullmove, which i btw used in diep
>around 1995-1998 already, it was pretty interesting thought
>back then, but in the end R=3 always worked better.

Although Heinz was the first to publish adaptive null-move pruning formally,
many people used it even before that. Donninger told me that in 1993 he used the
very same idea in NIMZO. In his article Heinz points out that Donninger hinted
at using R=2 in upper parts of the tree and R=3 in lower parts; but in fact
Heinz misunderstood Donninger's 1993 article since Donninger suggested exactly
what Heinz did.

>
>I have just to get a good compare run at Jan Louwman's auto232
>players with diep with 2 versions, the only difference being
>R=3 versus adaptive nullmove (last 4 plies R=2), and that
>DIEP then nearly gets a ply less deeply, it definitely was
>reflected in score. A big problem is to get above that
>10 simply for DIEP.
>
>>On July 13, 2002 at 10:50:52, Robert Hyatt wrote:
>>
>>>On July 13, 2002 at 02:07:17, Vincent Diepeveen wrote:
>>>
>>>>I still do not understand which positions you talk about which R=2
>>>>is finding and R=3 isn't.
>>>
>>>Note that he used fixed-depth.   This is therefore not surprising since
>>>some lines will be searched one ply shallower..
>>
>>
>>Of course. I merely did something like Heinz in "adaptive null-move pruning" (he
>>searched to fixed depths of 8, 10 and 12). But to get a clearer distinction, I
>>turned off checks in qsearch (that means in practice R=3 would perform better
>>than it did in those tests)

```