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Subject: Re: Search algorithms

Author: Dave Gomboc

Date: 11:14:08 11/07/03

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On November 06, 2003 at 22:31:49, Robert Hyatt wrote:

>On November 06, 2003 at 20:43:58, Dave Gomboc wrote:
>
>>On November 06, 2003 at 19:46:29, Robert Hyatt wrote:
>>
>>>On November 06, 2003 at 11:22:54, Dave Gomboc wrote:
>>>
>>>>On November 06, 2003 at 09:47:32, Robert Hyatt wrote:
>>>>
>>>>>On November 06, 2003 at 08:33:49, Gian-Carlo Pascutto wrote:
>>>>>
>>>>>>On November 06, 2003 at 05:45:53, Renze Steenhuisen wrote:
>>>>>>
>>>>>>>Depth-First Algorithms:
>>>>>>>  AlphaBeta (Fail-hard, Fail-Soft)
>>>>>>>  MTD(f)
>>>>>>>
>>>>>>>Best-First Algorithms:
>>>>>>>  SSS*
>>>>>>
>>>>>>The distinction between the three (and best-first and depth-first)
>>>>>>is very hazy, read "Research re: search and research" by Aske Plaat.
>>>>>>
>>>>>>--
>>>>>>GCP
>>>>>
>>>>>
>>>>>Eh?  The distinction is _huge_.
>>>>>
>>>>>One searches the tree in one direction and requires very little memory.  The
>>>>>other searches the tree in another direction and requires huge memory.
>>>>>
>>>>>I'm not sure how you could say that the distinction is very hazy.  They
>>>>>are as different as night and day...
>>>>
>>>>However, MTD(infinity) is equivalent to (searches exactly the same tree as) SSS.
>>>
>>>
>>>That's fine.  A best-first (breadth-first) search can search _exactly_
>>>the same tree as a minimax (depth-first) search also.  Doesn't mean a
>>>thing about how similar the two approaches are, however...
>>>
>>>However, the trees are grown differently.    I don't think any book I
>>>know of uses the actual search space as a way to define a search
>>>strategy...
>>>
>>>
>>>>
>>>>http://www.cs.ualberta.ca/~jonathan/Grad/plaat.phd.ps
>>>>
>>>>Dave
>>
>>Fine, but the point is that in this particular case, they are not as different
>>as night and day. :-)
>>
>>Dave
>
>They are different in the base algorithm.  They are different in their
>memory requirements.  They are different in the order in which they search
>the tree.  They are different in how hashing may (or may not) work.

They are *NOT* different in the order in which they search the tree.  The
traversal order is identical.

Dave



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