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
(I believe I set that because of that same chunking issue which we
discussed here before)
-jeff
--
Jeff McKenna
MapServer Consulting and Training Services
https://gatewaygeomatics.com/
_______________________________________________
gdal-dev mailing list
gdal-dev@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/gdal-dev
