[GRASS-dev] problem with GridModule

[Anna Petrášová]

On Mon, Nov 16, 2015 at 8:28 AM, Markus Neteler <neteler at osgeo.org> wrote:

> On Tue, Nov 10, 2015 at 7:58 PM, Anna Petrášová <kratochanna at gmail.com>
> wrote:
> > Hi,
> >
> > I am running viewsheds using the GridModule on 4 tiles. It runs, but the
> > result has some artificial gaps, see the attached picture (black is the
> > correct viewshed as vector and red and blue are wrong results). The
> problem
> > must be in the patching of the 4 tiles, because the tiles alone are
> fine. I
> > tried to run the same viewshed couple of times and it seems to behave
> > randomly, sometimes I get correct result, sometimes I get a gap. Any idea
> > what could be wrong?
>
> Can you adjust the number of cores being used? To see if it influences it?
>

I can't test right now, maybe later.

>
> > Maybe some bug in the pygrass raster library?
>
> Looks like a race condition?
>

I don't understand why would that happen, the patching done with pygrass
raster library is not running in parallel.

A workaround I currently use is to patch the rasters using r.patch, which
is in the case of viewsheds OK (the overlaps are the same), however in
other cases such as interpolation, the overlaps are different and r.patch
won't patch the rasters as desired, that's why the GridModule is using
pygrass raster library I assume.

Anna


> Markus
>
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