[thredds] HDF5 reading strategy in Thredds WMS

• To: <thredds@xxxxxxxxxxxxxxxx>
• Subject: [thredds] HDF5 reading strategy in Thredds WMS
• From: <Xiangtan.Lin@xxxxxxxx>
• Date: Mon, 23 May 2011 15:42:40 +1000

Hi all,

The BOUNDING_BOX reading strategy is used for file formats other than netCDF 
and HDF4 in Thredds WMS.

uk.ac.rdg.resc.ncwms.cdm.CdmUtils
public static DataReadingStrategy getOptimumDataReadingStrategy(NetcdfDataset 
nc)
{
String fileType = nc.getFileTypeId();
return "netCDF".equals(fileType) || "HDF4".equals(fileType)
? DataReadingStrategy.SCANLINE
: DataReadingStrategy.BOUNDING_BOX;
}

I'm working with a 8GB netCDF4/HDF5 file which has a 50000 * 50000 grid. With 
the BOUNDING_BOX reading strategy, it theoretically requires 9.3GB memory (for 
creating a float array of 50000 * 50000 entries), which leads to outOfMemory 
exception on my test machine.

I've tried to use the SCANLINE reading strategy by adding another OR condition 
(|| "HDF5".equals(fileType) to the above code, and it appears the outOfMemory 
issue is gone.

According to the documentation, the SCANLINE strategy is recommended for local 
uncompressed files, while the BOUNDING_BOX is recommended for remote and 
compressed files.

Can someone please advise whether it is OK to use SCANLINE strategy for my 
local uncompressed HDF5 files by modifying the above code?
Is there anything else I should be aware of?

Regards and thanks,
Lin