Le mercredi 04 juillet 2012 19:27:40, Jukka Rahkonen a écrit : > Hi, > > I feel that gdaladdo is not working optimally with any bigger rasterlite > tables. For example for my 153600x249600 pixel sized test image the > initial write into rasterlite took 3 hours and 10 minutes while adding > overviews with gdaladdo took 10 hours.
I tried a bit the gdal_translate part, but didn't have the patience to wait for it to complete (~ 1 hour on my PC). A sysprof profile shows that most of the CPU time ( ~ 75% ) is spent in zlib and libpng, which isn't surprising. I've tried to use tiles in geotiff with deflate compression, and it seems around twice faster, so png has a non neglectable overhead over plain zlib compression. But png seems to be smaller too. > Gdaladdo seems to use remarkable > much time every time it has finished with creating one overview layer. Yes, this is expected. Each overview layer is wrapped into a BEGIN / COMMIT transaction, so the commit at the end will take some time. Without that, I think things would be globally slower. > In > addition, the creation of the last overview layers does not feel as much > faster than I would have guessed keeping in mind that the number of tiles > to write goes 3/4 down at each step. As far as the perceived slowness on the last overview layer, reviewing the code, I don't see any obvious hint that would explain that. I tried on a much smaller dataset, and I could see that building overview level (n+1) uses as expected results from level n. So there's something more subtle. Once the overviews are built, is the reading performance of the overviews OK ? I'm wondering if there are not some indexes that should be added on the metadata table, perhaps on pixel_x_size and pixel_y_size, to speed-up tile retrieval. More generally, the rasterlite overview building does not use the generic overview code, but uses RasterIO() decimation. Not sure if this affects notably performance. > > I put my test image available for testing > http://latuviitta.org/documents/t80.tif (550 MB, deflate compressed tiff) > I will keep it on a server for a week or so. > > Commands I used were: > gdal_translate -of rasterlite -co driver=png t80.tif t80.sqlite > gdaladdo rasterlite:t80.sqlite,table=t80 > 2 4 8 16 32 64 128 256 512 1024 > > I tried to compare times with Rasterlite utilites rasterlite_load and > raster_pyramid but they both failed totally with my test image. > > -Jukka Rahkonen- > > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
