Le lundi 15 juin 2015 21:00:15, Nicolas Cadieux a écrit : > Thanks Even, > One last question about the buffer. Is 2GB is the max buffer size for > gdal_grid? If I select that, am I likely to run into problem with some > values?
The variable is a uint32 so you could probably go up to 4 GB. > Apart from trial and error, is there a balance that should be > stuck between available computer memory (currently at 64GB), input file > size and the buffer or can I simply select a 2GB buffer? As you're exploring new territories, I'd expect you to report how this works ;-) > > Merci beaucoup pour votre aide. > > Nicolas Cadieux M.Sc. > Les Entreprises Archéotec inc. > 8548, rue Saint-Denis Montréal H2P 2H2 > Téléphone: 514.381.5112 Fax: 514.381.4995 > www.archeotec.ca > > On Jun 12, 2015 17:29, Even Rouault <even.roua...@spatialys.com> wrote: > > Le vendredi 12 juin 2015 23:18:26, Nicolas Cadieux a écrit : > > > Hi Even, > > > Thank you very much. I increased the buffer to 1.5 GB > > > (512+512+514)*1024*1024 and I can now work much much faster with > > > gdal_grid. > > > > > > Does gdal_fillnodata have the same type of variable that could speed > > > things up? It is also slow and does not seem speeded up by the > > > "All_CPUS". > > > > No, no tunable for fillnodata, and it doesn't support multi-threaded > > parallelization. > > > > > I will use warp and the raster calculator in the future so you have > > > more magic up your sleeve, I would appreciate it. > > > > > > Cheers and thanks again. > > > > > > Nicolas Cadieux M.Sc. > > > Les Entreprises Archéotec inc. > > > 8548, rue Saint-Denis Montréal H2P 2H2 > > > Téléphone: 514.381.5112 Fax: 514.381.4995 > > > www.archeotec.ca > > > > > > On Jun 5, 2015 19:13, Even Rouault <even.roua...@spatialys.com> wrote: > > > > Le samedi 06 juin 2015 00:18:45, Nicolas Cadieux a écrit : > > > > > Hi, > > > > > I have been using gdal_grid to interpolate LiDAR data for some time > > > > > now. This would be a typical command: > > > > > > > > > > gdal_grid -l P0344_sol2004_XYZI_MTM8_CGVD28_150529 -txe 348733.0 > > > > > 401135.0 -tye 5568587.0 5773796.0 -a > > > > > nearest:radius1=3.0:radius2=3.0:angle=0.0:nodata=0.0 -outsize > > > > > 52402.0 205209.0 -of GTiff > > > > > H:/Nicolas/pytemp/OutPut\P0344_sol2004_XYZI_MTM8_CGVD28_150529.vrt > > > > > H:/Nicolas/pytemp/OutPut\P0344_sol2004_XYZI_MTM8_CGVD28_150529.tif > > > > > --confi g GDAL_NUM_THREADS ALL_CPUS > > > > > > > > > > As you can see, this is a huge raster and the csv. file (Pointed > > > > > with a .vrt) contains over a billion points. I am trying to do > > > > > this in one shot to avoid boundary effects. (I know I can split > > > > > this .csv file into smaller bits and make this more efficient). > > > > > The computer I am using has 12 cores, 64BG of memory (smaller than > > > > > the csv file) and a 1TB pcie solid state drive. It should manage > > > > > the task but it has been running for 5 days with less than 10% > > > > > done). I have access to a super computer with gdal if all else > > > > > fails. > > > > > > > > > > This is my question. The "--config GDAL_NUM_THREADS ALL_CPUS" or > > > > > "--config GDAL_NUM_THREADS 12" does not seem to work with the > > > > > nearest neighbor algorithm. (It seem to work with the -a count > > > > > command) If I use this on a smaller data set, I see no difference > > > > > in speed or cpu usage between using the "ALL_CPUS" or not using > > > > > this switch. Is this a bug or simply a limitation of the nearest > > > > > neighbor algorithm? > > > > > > > > Nicolas, > > > > > > > > The threading mechanism is generic for all algorithms . Add "--debug > > > > on" and you should see traces like "GDAL_GRID: Using 12 threads". > > > > Now, a reason for it not being efficient is that the work buffer > > > > used by gdalgrid (16 MB) is too small w.r.t to nearest speed. Hum, > > > > actually looking more closely at the code, I see that the quad tree > > > > to index the points will be rebuilt for each work buffer. This is > > > > likely the main cause of the inefficiency and why you don't see > > > > measurable differences between non threaded or threaded computations > > > > (since the building of the quadtree is not multithreaded). If you > > > > compiled from source, you could try changing the "const GUInt32 > > > > nDesiredBufferSize = 16*1024*1024;" line in apps/gdal_grid.cpp to a > > > > much higher value. A more proper solution would be to avoid > > > > rebuilding the quad tree for each work buffer. This is mainly code > > > > restructuring. > > > > > > > > An alternative to gdal_grid would be to use gdal_rasterize + > > > > gdal_fillnodata. This is usually much much faster, so you could try > > > > to check if it gives the results you expect. > > > > > > > > You could also try scipy : > > > > http://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.inte > > > > rpol ate.griddata.html#scipy.interpolate.griddata Not sure how it > > > > behaves with that number of points. > > > > > > > > Even > > > > > > > > > I don't want to move this > > > > > to a super computer if it will not multi-thread properly. > > > > > > > > > > Thanks, > > > > > Nicolas Cadieux > > > > > > > > > > (Gdal1.11.2 downloaded with OSGEO4W 64bit install with QGIS 2.8 on > > > > > windows 7_64) I use GDAL from the command line not from QGIS. > > > > > > > > > > > > > > > Nicolas Cadieux M.Sc. > > > > > Les Entreprises Archéotec inc. > > > > > 8548, rue Saint-Denis Montréal H2P 2H2 > > > > > Téléphone: 514.381.5112 Fax: 514.381.4995 > > > > > www.archeotec.ca > > > > > _______________________________________________ > > > > > gdal-dev mailing list > > > > > gdal-dev@lists.osgeo.org > > > > > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
