Author: Daniel Shawul
Date: 01:12:31 04/21/04
Go up one level in this thread
On April 21, 2004 at 03:57:50, Daniel Shawul wrote:
>On April 21, 2004 at 03:32:14, José Carlos wrote:
>
>>On April 21, 2004 at 02:52:12, Daniel Shawul wrote:
>>
>>>On April 19, 2004 at 20:38:47, Mike Siler wrote:
>>>
>>>>My program tries a null move search if
>>>>
>>>>1. it's not the endgame
>>>>2. it's not a PV node
>>>>3. it didn't just make a null move
>>>>4. it's not in check and wasn't in check on the previous ply
>>>>5. the remaining depth isn't so small that the reduced depth would take it into
>>>>the qsearch
>>>>
>>>>In general, only around 65% of the null move searches my program performs result
>>>>in a cut-off. Is this normal or do other programs tend to do better (and how)?
>>>>According to Ed Schröder's page, Rebel gets around 93-95%. I've tried the
>>>
>>>I am sure it does get that %. I just did a similar implementation like rebel's
>>> evaluate internal nodes
>>> if(score - our maximum hanging piece > beta)
>>> don't do null move
>>> This gives me usually >93% effectiveness! Thanks Ed.
>>
>> I don't know if Ed does only that, but in my experience it doesn't work. You
>>must also take into account your own threats or you'll do unnecesary full
>>searches. For example, eval is 0 and you have a hanging pawn, while beta is also
>>0. The opponent has its queen and rook attaked by your pieces. A null move will
>>save a lot of nodes there. The raise in % effectiveness is not enough to
>>compensate for that, in my experience.
>>
>> José C.
>
> sorry i made a typing error above
> if(score - our maximum hanging < beta)
> don't do null move
> Or
>
> if(score - our maximum hanging + opponent's maximum hanging < beta)
> don't do null move
I just tried this and it drops the effectiveness from 94 to 83%!
And then i checked the nodes searched to search a fixed depth of 9
[hashtable turned off] at the starting position.
nodes searched with the first one 1869125
nodes searched with the second one 1777845
that is roughly a 5% reduction.
I think you are right. I should use the second one
thanks
daniel
> The second one may solve the problem you mentioned.
>>
>>
>>>>recommendations listed there but they didn't help much.
>>>>
>>>>Michael
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