[GRASS-user] v.lidar.edgedetection very slow

Hamish hamish_b at yahoo.com
Fri Jun 19 22:54:09 EDT 2009

Michael wrote:
> I actually get the same thing.
> For the first while the process runs in full use
> of one core, but once the process starts writing results to
> the db, the whole process bogs down to a
> grinding halt. CPU usage for v.lidar.edgedetection
> drops down to ~1% (1% of one core) and sqlite usage rises to
> ~16%. Maybe I'm wrong, but my impression was that the
> bottle neck was the modifications to the database.

hmmm. I've seen no problems on Linux64 + DBF backend. 100% core until

Are you running WinXP + SQlite? Can you try with the DBF driver? 
maybe the common problem is in the SQLite driver...  ??

if you build from the latest grass 6.5 or 7 svn you can use the --verbose
flag to follow the action. setting 'g.gisenv set="DEBUG=1" gives you
even more detail (even with existing versions).

John wrote:
> Also, when I have tried to run v.oultier without db/topology
> it says it cannot as there is no database.

you can have a database without topology.

>  I will look at this again later. Maybe I am not selecting 3D when
> I have tried without db etc.

it needs that.

> Note that there is a bug in v.outlier. v.outlier
> creates a temporary table by the name of outfilename_aux (LN
> #137 /lidar/v.outlier/main.c) but elsewhere in the code it
> is hardwired to Auxiliar_outlier_table (LN's # 239
> & 258 /lidar/v.outlier/outlier.c) , so when it
> actually tries to write to the table it complains and fails.
> You can get around it by manually creating this table using;
> db.copy from_table=outfilename_aux
> to_table=Auxiliar_outlier_table
> I'm not sure why, but it looks like the
> system doesn't always need to use the Auxiliar_outlier_table, and
> when it doesn't, it continues on merrily without
> complaint. Unfortunately, when it does require the table, on my system
> the program continues on only to segmentation fault further
> down the line (at least it does on my system). Maybe
> it's because of the changes that I made to the code to
> correct the above error, but I can't see why that would
> be true. I was planning on looking further into it, but
> haven't had the time to start debugging. In the mean
> time I've added the files with my changes to the code
> for the developers. I'm a hack, so the changes are
> probably in poor coding practice. Someone
> more savvy that I will need to clean it
> PS. IF I find what I think are errors or
> possible improvements to the code, what is the most
> appropriate place and method to submit them?

please create your patches with "svn diff > somepatch.diff" and file them
in the trac system. Otherwise they quickly get lost and forgotten.




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