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Subject: Re: Tree Searching help

Author: Robert Hyatt

Date: 13:52:03 02/21/00

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On February 21, 2000 at 13:33:58, Christophe Theron wrote:

>On February 21, 2000 at 12:16:49, Tom Kerrigan wrote:
>
>>On February 21, 2000 at 11:37:52, Mark Taylor wrote:
>>
>>>An idea I had was to have a small incrmental value subtracted from the eval,
>>>this small increment getting larger the deeper into the tree search the eval was
>>>returned from. I had already done this for the values WON & LOST, but I
>>
>>This is a good idea. However, most chess programs have transposition tables. The
>>ideas are not compatible, because ttables assume that a position's score is
>>constant. You will probably want to have ttables instead of your penalty,
>>because once in a while there are huge benefits to having a ttable.
>>
>>>What I did in the end I made the first search iteration look at positional eval
>>>& material eval, then subsequent iterations looked at material eval only - but
>>>this was really a cop out.
>>
>>Yeah, I think this just confuses things. A long time ago I think there was a
>>program that ran on two CPUs. One CPU ran the regular evaluation function and
>>one was material-only. They checked each other. But programs these days get
>>along fine without material-only eval.
>>
>>-Tom
>
>
>The very old program Tech (I think the author was Gillogly, correct my spelling
>please, it was back in 1960) did this, but on only one processor I think.
>
>It played rather well, but was seriously handicaped by lack of deep positional
>understanding.
>
>
>    Christophe


No.  Tech was a 1970+ program.  The program that did two searches was called
"Phoenix" by Jonathan Schaeffer. He ran a normal search with several
workstations in parallel, and a "minix" search using several more workstations
in parallel.  Minix searched deeper looking only for tactical refutations of
the moves being considered by the normal search.

Tech was a very fast, very "dumb" type technology approach, which is where
its name came from (tech).  Jim occasionally posts on r.g.c.c and can be
reached there.



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