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Subject: Re: hash collisions

Author: Sune Fischer

Date: 08:04:34 07/10/02

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On July 10, 2002 at 09:30:30, Ricardo Gibert wrote:

>On July 10, 2002 at 04:30:28, Sune Fischer wrote:
>
>>On July 10, 2002 at 01:02:38, Ricardo Gibert wrote:
>>
>>>I find it fascinating that so many very experienced computer chess programmers
>>>do not understand some rather fundamental properties of alpha-beta search.
>>>
>>>What RH ran into was actually quite predictable. As MF put it, "I'm surprised
>>>that you're surprised."
>>
>>In a PV search some of the nodes are searched twice, so if you get something
>>outside the zero window because of a collision, it slows you down as you have to
>>research, but it doesn't hurt you unless you get another collision while
>>researching.
>>
>>-S.
>
>This is not a property of using PVS. A normal alpha-beta search plus hash table
>does this too.

How so?
I would say it does the opposite, since its about refuting moves.

But thinking further about it, the collision could also return a false score
outside alpha-beta, so the move is refuted when it should not be. I don't know
which is worse, but at least landing _inside_ is harmless as we just research,
which was my point.

-S.



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