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Subject: Re: Interesting mate test for hashing

Author: Dave Gomboc

Date: 16:57:09 09/11/99

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On September 11, 1999 at 18:01:30, Alessandro Damiani wrote:

>On September 11, 1999 at 17:58:59, James Robertson wrote:
>
>>On September 11, 1999 at 17:54:55, Alessandro Damiani wrote:
>>
>>>On September 11, 1999 at 15:56:10, Ed Schröder wrote:
>>>
>>>>On September 11, 1999 at 15:42:03, Robert Hyatt wrote:
>>>>
>>>>>On September 11, 1999 at 11:42:29, Ed Schröder wrote:
>>>>>
>>>>>>>Posted by Robert Hyatt on September 11, 1999 at 10:19:19:
>>>>>>>
>>>>>>>In Reply to: Re: Interesting mate test for hashing posted by Ed Schröder on
>>>>>>>September 11, 1999 at 01:43:12:
>>>>>>>
>>>>>>>On September 11, 1999 at 01:43:12, Ed Schröder wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>Do not underestimate the idea that in case there is no bestmove from the
>>>>>>>>hash table you do a full static evaluation of all nodes first and based
>>>>>>>>on that you pick the bestmove as being the first move you are going to
>>>>>>>>search for this (new) depth. The very early Rebel's (1981) worked that
>>>>>>>>way and I remember (although the system is very time consuming) it was
>>>>>>>>superior to all other systems I tried.
>>>>>>>>
>>>>>>>
>>>>>>>I'm not underestimating it.  I was simply saying that this approach can
>>>>>>>be applied when the position is encountered and there is no 'best move'
>>>>>>>in the hash table.  Rather than doing it when the hash entry is stored,
>>>>>>>and we are not even sure that this hash entry will ever be used again or
>>>>>>>that it won't be overwritten before it is needed.
>>>>>>
>>>>>>Right.
>>>>>>
>>>>>>>>I later removed the system because hash tables + bestmove was more powerful
>>>>>>>>at least for Rebel. But I wouldn't exclude the possibility such a system
>>>>>>>>can have a positive effect on the speed of the search.
>>>>>>>>
>>>>>>>>Actually I didn't remove the system but I replaced it with a faster one
>>>>>>>>that is:
>>>>>>>>
>>>>>>>>- generate all legal moves;
>>>>>>>>- for all moves do a (very) quick evaluation;
>>>>>>>>- sort all moves based on the quick evaluation.
>>>>>>>>
>>>>>>>>This (move ordering) system (for Rebel) is still superior.
>>>>>>>>
>>>>>>>>Ed
>>>>>>>
>>>>>>>
>>>>>>>Do you use killers, history, etc?
>>>>>>
>>>>>>Just the normal stuff.
>>>>>>
>>>>>>Order...
>>>>>>
>>>>>>- hash table move
>>>>>>- winning captures (ordered by expected material gain)
>>>>>>- promotion
>>>>>>- equal captures (QxQ etc)
>>>>>>- killers (4 of them)
>>>>>>- remaining moves ordered by the intelligent move generator
>>>>>>
>>>>>>The Killer History from Jonathan Schaefer gave no improvement for me.
>>>>>>
>>>>>>Ed
>>>>>
>>>>>
>>>>>It probably won't help if you keep 4 killers.  I didn't find any improvement
>>>>>in Cray Blitz either... but I did even more with killers.  I tried the current
>>>>>ply killers then the killers from _other_ plies if they were legal... adding
>>>>>history did nothing for me...  I probably ought to re-check Crafty again as it
>>>>>might be extra overhead for nothing now...
>>>>
>>>>I use 2 killers from the current ply (that's the normal way) and the 2 from
>>>>2 plies back. The latter gave me 5%.
>>>>
>>>>Ed
>>>
>>>I am surprised: history doesn't help? I think that the static ordering is good
>>>enough then. Perhaps history is good for those with a bad static ordering, like
>>>me?
>>>
>>>Alessandro
>>
>>History didn't help me at all either. I just ended up with a lot lower NPS....
>>
>>James
>
>Am I the last one with history heuristic here? :-)
>
>Alessandro

I doubt it, but it has to be said that KH (killer heuristic) and HH (history
heuristic) are competing with each other.  Having both may easily be slower than
just one of them.

Dave



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