I'm trying to do some clip process with a quile large layers but the process is too slow. When I see the task administrator, just around 28% of the CPU is being used. I've tried with 32-bit and 64-bit versions of QGIS 2.8 and 2.12. Same results: A clip of this layer takes hours, while ArcGIS 10.2 just needed 2 minutes. Does someone know what could be happening ??

  • 3
    So big difference must have a reason and using raw power is not the right solution. Would you be happy with 100% cpu usage and process still running for an hour or two? My bet is that QGIS does not utilize spatial index for selecting the candidate features for clipping. Describe your case in QGIS mailing list and perhaps developers will make a real fix in the future.
    – user30184
    Commented Feb 9, 2016 at 14:09
  • I know that you can enable multiple-core processing for visualization and rendering by assisting the rendering settings in QGIS. You can also enable 64 bit GRASS algorithms through the toolbox manager. Is it possible that the algorithms that QGIS relies upon for what you're doing are primarily built for 32 bit processing? Commented Feb 9, 2016 at 16:04
  • 1
    That's odd, especially considering reports such as donmeltz.com/arcgisqgis-faceoff. Which data sources are you using? Can you share test data?
    – underdark
    Commented Feb 9, 2016 at 17:46
  • 1
    I've got the same problem using disolve, it takes too long. As you can see in the image, CPU is at 28%, disc usage (SSD) at 0??? dropbox.com/s/wtftidndes5qv1a/2016-02-10%20%281%29.png?dl=0 Commented Feb 10, 2016 at 12:17
  • 2
    Same problem here using the Clip tool on a OSM-Road Shapefile (downloaded from Geofabrik). New Core i7 Machine (4Ghz) and 16GB DDR4 RAM plus m.2 SSD so it can't be hardware. When I try to clip the road shapefile with the border shapefile of the federal state (Saxony) it takes ages for the processing to run. 10 Minutes for 6% or so and CPU usage only shows around 20 to 30%. Where is the problem? QGIS 2.14.1
    – Phil
    Commented Mar 14, 2016 at 17:54


Browse other questions tagged or ask your own question.