[GRASS-dev] [bug #4827] (grass) Building topology for vector is incredibly slow

this bug's URL: http://intevation.de/rt/webrt?serial_num=4827
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Subject: Building topology for vector is incredibly slow

Platform: Mac OSX
grass binary for platform: Downloaded precompiled Binaries
GRASS Version: 6.1.cvs_060624

Raffaele Morelli
I am working with several vector files from Italy I have imported from shape files with v.in.ogr.
Those data comes with ISTAT census, so they are organized in several small polygons for each town (called "sezioni").
I wanted to produce a global national vector with polygons representing towns instead small areas inside towns, so I started running a shell script with all the "v.extract -d .. .... " to dissolve boundaries from the same town. Finally I came into a national vector map after patching the regional maps previously obtained gatering towns from the same region.

After this I launched a v.clean to remove duplicates,small angles and break poligons. The process runs normally but when it's time to build topology at the end of v.clean the process is incredibly slow.
After 50 minutes is still running and the building areas progress is at 33%!!!

is this 'normal'?

I hope I exposed clearly enough to help you.
Thanx anyway

-------------------------------------------- Managed by Request Tracker

this bug's URL: http://intevation.de/rt/webrt?serial_num=4827
---------------------------------------------------------------------

Subject: Building topology for vector is incredibly slow

Platform: Mac OSX
grass binary for platform: Downloaded precompiled Binaries
GRASS Version: 6.1.cvs_060624

Raffaele Morelli
I am working with several vector files from Italy I have imported from
shape files with v.in.ogr. Those data comes with ISTAT census, so they
are organized in several small polygons for each town (called
"sezioni"). I wanted to produce a global national vector with polygons
representing towns instead small areas inside towns, so I started
running a shell script with all the "v.extract -d .. .... " to
dissolve boundaries from the same town. Finally I came into a national
vector map after patching the regional maps previously obtained
gatering towns from the same region.

After this I launched a v.clean to remove duplicates,small angles and
break poligons. The process runs normally but when it's time to build
topology at the end of v.clean the process is incredibly slow. After
50 minutes is still running and the building areas progress is at
33%!!!

is this 'normal'?

run v.split before v.clean.

grass6/doc/vector/TODO says:

v.in.ogr
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It would be useful to split long boundaries to smaller
pieces. Otherwise cleaning process can become very slow because
bounding box of long boundaries can overlap large part of the map (for
example outline around all areas) and cleaning process is checking
intersection with all boundaries falling in the bounding box.

Hamish