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Subject: Re: Search algorithms

Author: Dave Gomboc

Date: 17:45:57 11/06/03

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On November 06, 2003 at 19:50:09, Robert Hyatt wrote:

>On November 06, 2003 at 11:23:36, Dave Gomboc wrote:
>
>>On November 06, 2003 at 09:49:33, Robert Hyatt wrote:
>>
>>>On November 06, 2003 at 09:33:28, Renze Steenhuisen 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.
>>>>
>>>>Done that already, but as Aske stated: they search the same nodes, but in a
>>>>different order.
>>>>
>>>>MTD(f) and the others are still DF algorithms, the second list works differently
>>>>(i.e., the order in which the nodes are expanded is different).
>>>>
>>>>Or am I talking rubish?
>>>>
>>>>Renze
>>>>
>>>>PS:  Am I missing algorithms (either important or not)?
>>>>PS2: Are Scout and NegaScout equal?
>>>
>>>
>>>They are just variations on the same idea.  All fall under the umbrella
>>>of alpha/beta depth-first search...  (this is in response to your question
>>>PS2).
>>>
>>>depth-first and breadth-first (best-first is one example of the latter)
>>>are totally unrelated other than the fact they both search a tree.
>>
>>Well, no.  Read Plaat's thesis.
>>
>>Dave
>
>
>I have read it.  It does _not_ say the two are equivalent in any shape
>or form, except for the actual tree searched in certain circumstances.
>Depth-first and breadth-first are completely different approaches to
>growing a tree, even if on some occasions they grow the _same_ tree.

In this particular case, the algorithms search the same tree.  Therefore, I
think it's reasonable to claim they are they are equivalent in some shape or
form -- not in all shapes and all forms, but at list with respect to the nodes
searched and the order in which they are searched. :-)

Dave



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