Jeff Whitaker

The release notes for libnetcdf 4.7.4 are [here](https://www.unidata.ucar.edu/software/netcdf/docs/RELEASE_NOTES.html). I don't see anything in there that would obviously effect the read speed for slices. I have confirmed that it is very...

strides are all 1 here (nc_get_vara is used)

I suspect it has something to do with the chunksizes and/or the zlib compression. If I rewrite the file in netCDF classic 64-bit format (`nccopy -6`) the test script runs...

Is it possible for you to avoid the loop? If I use ```python q=nf['s_an'][0,:,0:100,0:100] ``` the test runs in less than 0.1 seconds.

It's a performance regression in the C library. I've posted a C version of your test program to demonstrate this at Unidata/netcdf-c#1757.

I have tried using the `Variable.set_var_chunk_cache` method to reset the chunk size for the variable before slicing it, but this has no effect. Unfortunately, there currently is no hook for...

netcdftime is being split out into a separate package. I created a copy of this issue at https://github.com/Unidata/netcdftime/issues/11.

You definitely shouldn't get a crash. Does this simple example work for you? ``` from netCDF4 import Dataset import numpy as np nc = Dataset('test.nc','w') vlen_type = nc.createVLType(np.float,'vltest') nc.createDimension('x',None) v...

Confirmed. Seems like a C library issue though. If you comment out the print statements in your example, it does not crash. However, running `ncdump` on the resulting file does...

Perhaps it would be sufficient to attach the netcdf file generated by the example code above to a netcdf-c issue.