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Subject: Re: Search algorithms

Author: Robert Hyatt

Date: 09:43:29 11/08/03

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On November 07, 2003 at 14:16:16, Dave Gomboc wrote:

>On November 06, 2003 at 22:42:14, Robert Hyatt wrote:
>
>>On November 06, 2003 at 22:33:04, Robert Hyatt wrote:
>>
>>>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.
>>
>>
>>BTW,  I hope you don't try to convince me all sort algorithms are
>>equivalent, just because they take the same list and produce the
>>same final result.  :)
>
>Well, what is correct is that the node expansions are done in the same order.
>
>Dave


Again, what two algorithms specifically are you comparing?  Best first
and depth-first _never_ expand the nodes in the same order, except for
trees where each side has only one legal move at every position...




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