[Qgis-user] slow start up

Craig Leat craig.leat at gmail.com
Mon Jan 18 07:09:46 EST 2010


Greg Coats wrote:
> Using Qgis version 1.4.0 built against code revision 12644:12645M
> from http://www.kyngchaos.com under Mac OS X 10.6.2, I find that
> starting up from the .qgs project file takes 4 minutes, and during this
> time Activity Monitor reports that Qgis is consuming 99% of the CPU.
> The largest file in the project is only 37 MB. The computer has a 2.33
> GHz Intel Core 2 Duo processor, with 3 GB RAM. AFTER start up, Qgis
> quickly pans and zooms in and out through the imagery. Only ONE
> raster image is drawn at any particular scale. What is Qgis doing at
> start up that requires it to use 99% of the CPU for 4 consecutive
> minutes? What can be done to reduce the start up time? I am
> interested in hearing from others how long Qgis takes to start up.

Four minutes to startup! Not bad, considering I have project files
taking ~25 minutes to load. I haven't read the code :-) but my
impression is that QGIS scans every raster file when the project is
opened to collect essential information it needs to interact with the
files. It's not only file size that's important, but also the number
of files. There was a suggestion on this list or the developer list
(can't remember) some time ago (September 2009?) that pointed to
combining several rasters into a virtual catalogue (gdal vrt) to
improve performance. In my tests performance actually dropped by a
factor of three, but your mileage may vary. I suggest you experiment a
bit.

A question to any devs following this. Is it practical to write the
information QGIS collects at startup into the project file or another
file to have it readily available the next time the project is loaded?

Regards,

Craig.


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