[GRASSLIST:1720] Re: GRASS 5.7: Vector networking tutorial

Radim Blazek blazek at itc.it
Mon Nov 10 08:23:25 EST 2003

On Sunday 09 November 2003 23:16, Greg Sepesi wrote:
> Here are the results of running dgtable (i.e., Directed Graph
> implemented with lookup tables) ShortestPath variants on the FRIDA
> data.  The screen dumps come from a Windows application in which I'm
> using dgtable to conflate vector maps.  I'm also using dgtable in the
> creation of vector maps for handhelds running Palm OS.  I believe the
> last Shortest Path variant (i.e., points to graph) is equivalent to the
> reportedly slow v.net.iso function.


> shortest path variant: points to graph
> dgtable function:      FindShortestPathMultipleStartingPoints (with
> destination argument = 0)
> example application:   planning location of distribution warehouses
> screen dump:           http://www.eduneer.com/dgtable/sp11.png
> execution time:        0.44 seconds
> comments:              green circle represents starting point
>                        green lines are middle third of cost range
>                        yellow lines are final third of cost range
>                        red lines are not reachable (as defined by the


On 1.5GHz processor v.net.iso takes 
9m 39.372s for current cvs version and 
    1.867s if cache is enabled
In this case (this data) the result is the same, but there is a bug in cache,
which may cause bad results in certain cases.
The time includes writing vector and building topology, v.build on the result
takes 0.988s. 
I think that 1.867s is not bad, the problem is the bug in cache.


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