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Subject: Re: Rehashing

Author: Don Dailey

Date: 11:37:34 01/19/98

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Stuart,

I have had no success with rehashing.  I save and store positions
well into the quies search unlike most of the program here though
so it might change things.  Once your table fills up you will have
to overwrite something and will be doing some work to find the
best candidate.   From my discussions with others, most do not
rehash either.  I would still give it a try though.  One idea
is set associativity.  I'm pretty sure Cray Blitz used this but
not positive.  Bob should have some good ideas for you.

One idea I want to research is the concept of "key positions."
Certain hash entries may be overwhelmingly important compared
to others and perhaps should NEVER be overwritten.  Like key
positions in the Ruben Fine 70 ending.   I don't know if it's
possible to identify these but it could be a minor breakthrough
if we could.  Nahhh...

- Don



On January 19, 1998 at 14:01:30, Stuart Cracraft wrote:

>I plan to implement simple linear rehashing.
>
>Right now, my hash table is not very good and doesn't give
>good numbers. I'd like to fix that first but haven't found
>the fix. My numbers are typically under 10% (e.g. total
>probes successful / total probes tried) for the regular
>transposition table (pawn hash table is always very high and
>seems okay.)
>
>Anyway, I'm hoping that this <=10% number for the main transposition
>table will take a jump up after rehashing.
>
>If anyone has implemented rehashing and tested after implementing
>it, I'd be interested to know what you saw. And I'll report back too.
>
>--Stuart



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