Dear Alasdair,
thank you for your details on Depthmap algorithms and the hint with the
b*tree.
So far we have our VGA routine running with an expanding ring (only upwards
so as not to check individual connections twice) as well, but
intervisibilities and depth steps stored in system-size matrices for each
grid point, with just basic iteration so as not to have to search a list. It
works ok but we use it to evaluate fitness in a GA (roll eyes) which of
course multiplies any delays, so it might be worth restructuring. I just
found it hard to predict whether establishing a more complicated data
structure in the first place would save us any time - probably depends on
the small-world qualities of the individual graph.
Joerg
--
Joerg Kraemer, Jan-Oliver Kunze
Diplomanden FG Finn Geipel, Technische Universitaet Berlin
Ackerstrasse 71-76, Raum 438, 13355 Berlin, Germany +49 30 31472748
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> -----Original Message-----
> From: [log in to unmask] [mailto:[log in to unmask]] On
> Behalf Of Alasdair Turner
> Sent: Friday, April 15, 2005 10:06 PM
> To: [log in to unmask]
> Subject: Re: Seeking a list of space syntax algorithms
>
> Dear Jorg,
>
> In order to make graph connections, Depthmap simply uses an expanding
> ring around the current grid point -- I believe it's a fairly standard
> technique, although probably not the fastest -- if I were doing it again
> I would use a B*-tree (do a Google search to find online algorithms). I
> believe Yiorgos Chrysanthou (Google once more) coded the version used in
> Sanjay Rana's Isovist Analyst extension.
>
> As for integration the analysis, Depthmap just uses a straight forward
> breadth first search -- any algorithm book should be able to give you as
> good a algorithm as used in Depthmap -- there are no hidden
> optimisations, although I would say that it is very well written! :-)
>
> Alasdair
>
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