[Qgis-user] slow start up

[William Kyngesburye]

On Jan 18, 2010, at 6:09 AM, Craig Leat wrote:

> 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?
> 
I was able to shave off a minute or so by making sure all the vrt rasters had custom min/max set in the rendering propoerties.

I alos noticed that it takes a while to turn off and on the vrt rasters, and open their properties windows.

-----
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
http://www.kyngchaos.com/

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