BTreeMap instead of HashMap about netcdf

[evomassiny]

Good idea ! I don't think performance matters much in this part of the code, so i don't see why not :)
@mhiley do you agree ?

[mhiley]

I agree @evomassiny. @pick2510 Feel free to submit a PR!

[pick2510]

Thx for the feedback.
Unfortunately I found out that BTreeMap doesn't preserve the order of insertion. Instead the data gets ordered alphabetically by the keys. Even though this is nicer than unordered, it doesn't solve my problem how I thought.
A vector would satisfy the order preserving criteria. But that would involve a lot of changes in your code.
I'm not sure if the advantage is worth it...

[bluss]

You could drop in indexmap or another deterministically ordered hashmap. Indexmap doesn't do full insertion order, but it is a deterministic iteration order. (It swaps items around if you remove them from the map).

[magnusuMET]

8f44ba8 makes iteration over variables, attributes, and dimensions deterministic.