On vendredi 3 janvier 2020 14:02:18 CET Jeff McKenna wrote: > Hi Joaquim, > > I have tested your file on Windows 10 here, with the command: > > gdalinfo grav_29_img.nc -mm > > which takes about 5 seconds to execute fully. I am using MS4W 4.0.2 > (GDAL 2.4.3 , NetCDF 4.7.3 )
Jeff, Do you build netCDF with a custom value of the CHUNK_CACHE_SIZE / chunk-cache- size setting ? With the default (4 MB), runtime on my machine is about 7 minutes. But if I use --with-chunk-cache-size=67108864 as in https://trac.osgeo.org/gdal/ticket/5291#comment:26 , then it goes down to 9 sec. So this is a quite old known issue with the netCDF driver with HDF5 chunking & compression. Due to the netCDF driver exposing rasters with a north origin, and netCDF Y origin being at south, there's a mismatch between GDAL blocks and netCDF chunks. So for the sake of simplicity, the netCDF driver exposes one single line as the GDAL block size. It could/should be improved to make a better use of netCDF chunks, so as not being too much dependent of the quite pessimistic default of the netCDF chunk_cache_size. Even -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
