#18843: Differentiable manifolds: vector fields and tensor fields
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Reporter: egourgoulhon | Owner: egourgoulhon
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-7.3
Component: geometry | Resolution:
Keywords: differentiable | Merged in:
manifold, tensor field, vector |
field, differential form |
Authors: Eric Gourgoulhon, | Reviewers: Travis Scrimshaw
Michal Bejger |
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/manifolds/diff_manif_tensor_fields|
3ab0af048e9ba51f09752a02f0d6544a53ffe15e
Dependencies: #15916, #18783, | Stopgaps:
#20770 |
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Comment (by egourgoulhon):
Replying to [comment:35 tscrim]:
> Okay, here's the first round.
Thank you very much for reviewing this!
> Overall, the code looks okay, but I haven't check things in detail yet.
I've made my way through most of the doc; there are likely some other doc
fixes that I will need to do, but I've done a fair bit of clean-up.
However, there are some issues:
>
> - To run the tests on `tensorfield.py` takes ~172 seconds (that is after
marking a bunch of them as `# long time`). This is too long IMO, and we
need to either find a way to speed things up or simplify the tests somehow
(smaller manifolds perhaps?) so they don't take so long. One or two non-
trivial top-level examples are good. For the doctests, it just needs to be
small examples showing the functionality. For any more complicated
examples needed to do a more complete test should either be relatively
small (in terms of number of lines) and be marked as `# long time` or you
need to have a separate file with the complete examples where most (all?)
tests are marked as `# long time`.
OK I will try to shorten significantly the doctests.
>
> - I'm not sure about importing `xder` into the global namespace.
`exterior_derivative` I am okay with since it is explicit, but `xder` is
not a descriptive name IMO. If you want it, then you can import it in your
`init.sage` file (in the `~/.sage` folder).
I agree `xder` is not as descriptive as `exterior_derivative`. Certainly
the latter should be the primary function name. However for the end user
manipulating a lot of differential forms, it is certainly desirable to
have a short name (in addition to TAB completion), as `diff` is a short
name for `derivative`. We may even think of a shorter name, like `xd`, as
a reminder of the standard mathematical notation '''d'''.
>
> - I added some long versions of each of the names. It is good to at
least have the long name. I actually changed `exterior_der` to
`exterior_derivative`. I am not opposed to having an alias to `xder`
though.
>
> - While in general, it is good to adhere to 80 character lines,
sometimes it just makes it harder read (which is why it is a guideline). I
exercised some judgment and made some lines go over this because IMO they
become easier to read.
OK.
>
> - We will probably want to use the coercion framework, so `__mul__`
which handles the scalar action should become `acted_upon` or `_rmul_`
(and `_lmul_`).
Yes, this seems desirable. I'll try it.
>
> I believe this is the biggest of the remaining !SageManifolds tickets,
Yes, certainly.
> so we just need to power through this and the rest should be easy...
--
Ticket URL: <https://trac.sagemath.org/ticket/18843#comment:36>
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