Hello, I found a workaround to my problem : the computation I am performing is done on a layer open from a network file. So I copied the files on my local computer disk and the computation time became normal, with a normal CPU usage.
In order to understand the problem, I had a look to questions on slow network access trouble with QGIS. I think my problem is related to that one : http://hub.qgis.org/issues/6448 In fact if I try to perform a simple "spatial query" with Qgis onto a layer opened for a network file, the computation is very slow and does not use more than few percents of CPU. The same query done on a layer opened from a local disk file is normaly performed. I hope this could help anyone facing this performance problem. Thank you for your attention Alain Gauthier _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
