[GRASS-dev] r.sim.water buffer overflow

[Hanlie Pretorius]

2010/8/18, Markus Neteler <neteler at osgeo.org>:
> On Wed, Aug 18, 2010 at 8:31 AM, Hanlie Pretorius
> <hanlie.pretorius at gmail.com> wrote:
>> Hi,
>>
>> I'm posting here because I had no reaction on the users email list.
>
>
> (Hint: if you post an example for a sampe data set like Spearfish or
> North Carolina, then it is way easier to reproduce for us...)
>
>> I'm using GRASS64 RC6 on Linux 10.04 (64-bit) and I'm trying to run
>> r.sim.water on a catchment about 5000 km2 in size.
>>
>> I started with a very fine resolution in my region (00:00:00.18) and
>> got the following:
>> -----
>> GRASS 6.4.0RC6 (world_wgs84):~ > r.sim.water
>> elevin=lieb_dem_25m_clipped dxin=lieb_dem_25m_clipped_dx
>> dyin=lieb_dem_25m_clipped_dy  rain_val=2.0 manin_val=0.1
>> infil_val=13.0 depth=rsimwater.depth.18s disch=rsimwater.disch.18s
>> default nwalk=600505650, rwalk=600505650.000000
>> Killed
>
> Here for NC:
>
> g.region -d res=1000 -p
> r.slope.aspect elevation=elevation dx=elevation_dx dy=elevation_dy
> r.sim.water elevin=elevation dxin=elevation_dx dyin=elevation_dy  \
>         rain_val=2.0 manin_val=0.1 infil_val=13.0 \
>         depth=rsimwater.depth.18s disch=rsimwater.disch.18s
> ...
> WARNING: Infiltration exceeds the rainfall rate everywhere! No overland
>          flow.
> ...
> Number of iterations = 0 cells
> Time step = 129663.85 s
> GRASS 6.4.0svn (nc_spm_08):~ >
>
> So no crash. But my region had way less pixels.
>
>> ----
>>
>> Since this resolution gives about 300 million cells in the region, I
>> progressively coarsened the resolution, but I get buffer overflows
>> even with just 2736 cells in the region (resolution = 00:01:00)
>
> The question is; how big are the internal tmp files?
> Did you compile GRASS with large file support (--enable-largefile)?
>

I did not compile GRASS myself - have not tried that before - so I
just used the version as the Ubuntu package manager installed it.

I will try to find out how to compile GRASS and then use to options to
enable large file support and the debugging symbols.


>> Below is an example of the error I got at a resolution of 1 minute.
>> The output at all resolutions (except 00:00:00.18) is similar:
>
> Second possibility is a bug when having LatLong coordinates. I
> used a metric system.
>
> ...
>> Time step = 0.00 s
>> *** buffer overflow detected ***: r.sim.water terminated
>> ======= Backtrace: =========
>
> We would need a full backtrace (maybe not posted to the list)
> which requires GRASS compiled with debugging symbols.
>
>> I can run the Spearfish example as shown in the r.sim.water manual
>> page and that region contains 2654802 cells.
>
> Could you prepare a LatLong example with public data?

I will get the Spearfish dataset into a LatLong location and see what
happens when I run r.sim.water on that. I could place the Spearfish
latlong location on a temporary web site if needed.

>
>> My DEM is not rectangular and I'm setting the region to a vector file
>> that is an irregular boundary. So, the DEM has NULL values outside the
>> vector boundary but inside the region. Could this be a problem?
>
> I don't think so.
>
> Markus
>

Thanks for the help.