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Subject: Re: Search algorithms

Author: Robert Hyatt

Date: 19:33:04 11/06/03

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On November 06, 2003 at 20:45:57, Dave Gomboc wrote:

>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


I don't believe that last is correct. IE with respect to order.  Particularly
comparing members of the breadth-first family to the depth-first family and
not just picking one specific algorithm from each.




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