Argument 'count' in NetCDF is not exactly the same as the 'count' in
H5Sselect_hyperslabs(space_id, op, start, stride, count, block).
When the argument 'stride' is NULL, NetCDF's 'count' should be used in
argument 'block', for example,
H5Sselect_hyperslabs(space_id, op, start, NULL, ones, count);
where 'one' is an array of all 1s. Although using NULL 'block' below
H5Sselect_hyperslabs(space_id, op, start, NULL, count, NULL);
has the same effect, HDF5 internally stores the space of a subarray as a
list of single elements, instead of a "block", which can affect the
performance.