[geos-devel] GEOS robustness question

Kevin Wiebe Kevin.Wiebe at safe.com
Tue Jun 24 15:45:56 EDT 2003

> Kevin,  I'm afraid I don't have the time right now to provide a
> detailed explanation.  If you start browsing the relate classes
> you'll find the code you're looking for.  Best to look at JTS,
> I think - the algorithms are the same and the syntax is clearer.
> Get an IDE which helps you drill down through the code.
> Martin Davis, Senior Technical Architect
> Vivid Solutions Inc.
> Suite #1A-2328 Government Street   Victoria, B.C.   V8T 5G5
> Phone: (250) 385 6040    Fax: (250) 385 6046
> EMail: mbdavis at vividsolutions.com  Web: www.vividsolutions.com

Thanks, Martin.

I've drilled around for a while already and I guess I was just trying to get some confirmation on what I've seen.  It looks to me like fairly complex intersection/topology/graph structures are created and the entire matrix is correctly populated for every predicate call.  That is, it seems all of the squares in the matrix are determined even though the specific predicate called really doesn't care about some of the entries.  It also appears that intersection points are generated when one wants to know if two shapes cross or intersect.  It also appears that if I want to call a predicate on A&B, followed by one on A&C, it is not possible to cache any intermediate processing on A between calls, like the monotone chains, spatial indexes, and the like.

Don't take this to be criticism as much as the recognition that solutions to difficult operations such as these don't come with simple algorithms.

I'll keep digging, but feel free to correct me if my view so far is off.


 Kevin Wiebe     Safe Software Inc.       email:kevinAtsafe.com
      Senior     Surrey, BC, CANADA       phone: (604) 501-9985
   Developer     http://www.safe.com        fax: (604) 501-9965

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