[GRASS-dev] v.build: why is attaching islands taking so long?

[Hamish]

Maciej Sieczka wrote:
> Can anybody possibly explain why does the "Attaching islands..." in
> v.build take so very long compared to other operations? 
> For example: I have a big vector map consisted only of lines, more than
> 180 000 of them. v.build on this dataset takes about 20 seconds. After
> converting lines into boundaries (v.type), v.build on that new vector
> map made of boundaries only takes half a day, with 99% of processing
> time dedicated to "Attaching islands...". Is that normal? Any
> improvements possible?

the not-thinking-about-it-much guess is to blame the "florida coastline"
problem. to test is that is the problem, try running 'v.split vert=1000'
before v.type and see if it still takes a long time.

you might try running a subset through a profiling tool if you like:
  http://grass.osgeo.org/wiki/GRASS_Debugging#Using_a_profiling_tool


does the boundary data contain many small slivers?


Hamish