On vendredi 3 janvier 2020 16:03:47 CET Jeff McKenna wrote: > On 2020-01-03 3:52 PM, Even Rouault wrote: > > 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. > > Hi Even, > > No I don't set CHUNK_CACHE_SIZE during compile at all. I do however set > USE_HDF5=OFF
Ah, that explains it all then. The file is thus opened by the HDF5 driver, not the netCDF one. And I also do get the 5 sec when forcing the HDF5 driver. But you loose the whole netCDF specific logic, and in particular georeferencing. Even -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
