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Subject: Re: Replacement shemes

Author: Vincent Diepeveen

Date: 11:13:21 07/27/03

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On July 27, 2003 at 14:06:33, Amir Ban wrote:

>On July 27, 2003 at 13:51:28, Sune Fischer wrote:
>>I've been trying some different hash schemes, and the one
>>that should be the best completely fails to solve a few positions.
>>Currently I use two tables, one of the criterias is to replace if it is the
>>same key (so I don't get the same key in both tables, same philosophy as with
>>killers moves), but only if the depth is greater or equal.
>>For some reason this fails on fine70 and similar positions.
>>If I do always replace on top of _the same_ key, then it works fine!?
>>I don't see the logic in that, and I'd really prefer to keep the deeper entry,
>>Could this indicate a bug, or can it be explained/fixed?
>>Currently I'm trying replace if LOWER bound (beta cut) or deeper, seems to work
>>well also, I still don't get it though.
>I observed the same.
>The reason seems to be that the deepest result is often useless in producing
>cuttoff/narrowing due to wrong relation/score.

No problems in diep replacing the same position. It happens seldom that i didn't
already get a cutoff from hashtable (either alfa,true or beta bound)
when this depth is smaller than stored depth. I only overwrite when depth >=

Works great with 8 probes and always overwrite strategy which doesn't overwrite
in 1 case and that's when the position is already in hashtables with the same
side to move and with bigger depth stored.

Perhaps you are not having truebounds in hashtable stored in combination with
alfabeta dependant forward pruning that takes care big score swings from <= alfa
to >= beta and vice versa?

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