[Qgis-user] Qgis low CPU and Memory load

[Wolfgang Meinolf]

Thanks for the excellent feedback and hints. First of all, my QGIS qork is mainly with vector layers. Therefore unfortunately the OpenCL capabilities don’t help. To my understanding this is mainly for accelerating heavy raster calculations. Secondly and as already mentioned, my most urgent need is to accelerate the execution of GRASS v.net.steiner and v.clean as part of my toolbox processing scripts for a number of given route networks in separate areas.

However, on you feedback I searched a bit and found, that obviously  since QGIS3 some parallelization seems to be supported. In the developers coockbook here: https://docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/tasks.html#task-from-a-processing-algorithm  I found some promising info including the link to here: https://www.opengis.ch/2018/06/22/threads-in-pyqgis3/. I will spend some time to modify my loop through my separate network areas to try, to start python jobs from inside the loop, which are then collected at the end.

Thanks again for your good ideas and have a good weekend
Br
Wolfgang
-------------

Hi,

You can also activate the OpenCL option.  Some algorithms have been optimized (I believe it’s still experimental).  If you have a compatible  OpenCL video card, it will run these on the card.  If not, it can probably run on compatible CPUs.

https://www.itopen.it/opencl-acceleration-now-available-in-qgis/

I find it’s worth testing equivalent algorithms from different sources in the Processing plugin is worth the trouble.  Some Saga algorithm are faster.  Merging vector lines, for example, could take a long time using the QGIS algorithm (talking hours) and was much faster (a few minutes) using the Saga version of the tool.  I also found that some algorithms are much faster to handle when the files are not open beforehand in the layer manager.  For example, the Processing plugin can sometimes grab the needed files directly on the hard drive rather than picking one that is already open in the layer manager. Looking at the processor, memory and disk usage can also help identify bottle necks in the hardware.
Nicolas Cadieux
https://gitlab.com/njacadieux


Le 16 avr. 2021 à 03:34, Francesco Pelullo <f.pelullo at gmail.com<mailto:f.pelullo at gmail.com>> a écrit :


Il ven 16 apr 2021, 02:56 Stewart Holt <stewartbholt at gmail.com<mailto:stewartbholt at gmail.com>> ha scritto:
 Parallelizing script execution is complex and I doubt that it is currently done in QGIS.

That's true.

In Settings / Options / Rendering / there's a checkbox for render layers in parallel using as many CPU cores you want, but It Is enabled by default so I suppose that there are no others settings that could make QGIS more aggressive in CPU usage.

Regards



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