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Subject: Re: hash entry replacement schemes (more)

Author: Dave Gomboc

Date: 04:44:18 09/15/02

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On September 15, 2002 at 04:27:44, martin fierz wrote:

>i wish i knew :-)
>i've forgotten what exactly i did in my 2-table code. i think i kept my
>"important table" relatively empty, and probed "forever" until i found a place
>to store the entry. "forever" was usually once, but on occasion more.
>i never quite figured out why this turned out to be less efficient than a single
>table. it's well possible that my implementation was bad... the other thing i
>thought about was that in checkers, you often have a situation where you can
>reach the same position with variable depth - happens in any endgame with kings.
>now, i was relying on the depth from root to select the table i was probing in.
>if a position stored in the "important" table turned up deeper in the search, it
>might not have been found because it was looked up in the wrong table. the whole
>thing with two tables seemed more complicated than with one, so i threw it out -
>besides, the difference is probably really small, even with a better
>implementation.
>
>aloha
>  martin

It seems to me that other things being equal (e.g. you use them in the same
way), one table with two slots is going to be slightly more efficient -- or at
least certainly not less efficient -- than two tables with one slot, due to
better prefetching and caching behaviour.

Dave



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