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From: AST@postman.hsn.no (Alf Steinbach)
Subject: Re my response to: Help (A* as applied to shortest path problem)
Sender: news@news.uit.no (News admin.)
Message-ID: <AST.166.784322885@postman.hsn.no>
Date: Tue, 8 Nov 1994 19:28:05 GMT
Lines: 26
References: <39o8bl$lfe@utdallas.edu>
Organization: Nordland College

In article <39o8bl$lfe@utdallas.edu> shnayd@utdallas.edu writes:
>From: shnayd@utdallas.edu
>Subject: Help (A* as applied to shortest path problem)
>Date: 8 Nov 1994 10:17:57 -0600

Whoops!  I can see why you didn't really understand it.  A few seconds
after hitting the return key ("Ok to send?"  -  yes, yes, yes...) it hit
me:  you shouldn't overestimate,


   you should UNDERESTIMATE.


Always.  That way, you're guaranteed to expand all nodes which *can* have
a shorter path to the goal than the one currently being considered shortest.
If you overestimate (say, an estimate of very very large dist), then you can'
t be sure to expand all possible best paths, because one which is shorter may
*appear* to be longer, based on the large estimate, and wouldn't expand.

Hope this helps.  Sorry about the first response...  But I generally just
type whatever runs into my head, and check it afterwards.  Works well using a
wordprocessor, but (as I now see) not on the net!

Complete fool, etc.,

- Alf
