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Subject: Re: Dr Hyatt : hash collisions and short keys

Author: Robert Hyatt

Date: 21:18:40 08/20/02

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On August 20, 2002 at 22:44:28, Russell Reagan wrote:

>On August 20, 2002 at 21:52:05, Robert Hyatt wrote:
>
>>That's backward.  A hash hit near the root saves a _huge_ amount of work.
>>Just think how big the sub-tree is one ply away from the root, compared to
>>the sub-tree one ply away from a tip position...
>
>His concern was that a false hash hit near the root would cause a blunder. If
>you didn't probe for the first (say) 2 plies, you'd still get that same result
>from the hash hit you got at ply 3, right? Maybe I'm not thinking about it
>correctly, but as far as I can tell, the only *extra* work you're doing here is
>a 2 ply search, which is nothing. Unless I'm missing something (which wouldn't
>be the first time...)
>
>Russell


You are doing a (say) 12 ply search.  If you probe at ply=2 you might get a
false hit, or not.  But if you get a hit of any kind, you stop that branch at
ply=2 and avoid a 11 ply search.

That is a _lot_ of work to avoid...




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