Differentiable local field projection

[yaugenst-flex]

No description provided.

[tylerflex]

👀

[tylerflex]

a few comments. I'm mostly a little confused about the base.py stuff?

[tylerflex]

Some comments.. Mostly things I thought could be refactored, renamed, simplified.

Otherwise I think it's consistent / correct. Only thing I'm not 100% sure on is in the DataArray.static property.

vals = self.values if self.values.size == 0 else np.vectorize(getval)(self.values)

will getval work if self.values is a np.ndarray of dtype=object?

otherwise feeling pretty good about it in its current state

[yaugenst-flex]

@tylerflex There are some changes to DataArray properties here. The naming and mechanics of these are probably not ideal, but since it's not user facing let's address them in the DataArray refactor? We'll end up changing most of these things anyways.
Also, #1939 lists this for 2.8rc1, should I rebase on pre/2.8? Although I think it makes sense to include this only with the gradient fixes in develop. So either as part of 2.7.3 or rebase to pre/2.8 only after develop is merged.

[tylerflex]

Also, #1939 lists this for 2.8rc1, should I rebase on pre/2.8? Although I think it makes sense to include this only with the gradient fixes in develop. So either as part of 2.7.3 or rebase to pre/2.8 only after develop is merged.

@momchil-flex what do you think? basically there were some changes in my (recently merged) #1923 that Yannick used in this PR. So ideally we would do another develop -> pre/2.8 merge before Yannick rebases against 2.8?

[momchil-flex]

@yaugenst-flex what do you think will be simplest? I'm already running notebook tests for 2.7.3 and since it's hard to tell if this PR may not have various small effects, I'd rather not include it for now. However we could merge it to develop after 2.7.3 and then eventually into pre/2.8, or we can merge develop into pre/2.8 again and then you rebase the PR. Either way it will likely only come out in 2.8.0rc1 since we may not do any other 2.7. patches, but if we did the first approach would put it in there too.

[yaugenst-flex]

@momchil-flex I think it makes sense either way to merge develop into pre/2.8 after the 2.7.3 release so we keep them somewhat in sync. I'll rebase to pre/2.8 after that, shouldn't be a problem.

[tylerflex]

Looks really good! thanks @yaugenst-flex . I dont know if you want @QimingFlex to look at the field projection bits? I couldn't understand most of the physics of the operations, but did follow through the code and thought it looked good.

[yaugenst-flex]

Hey @QimingFlex, would be great if you could have a quick look at the field projection bits in this PR, I reworked some of it to more easily accomodate autograd. I did try to make sure that all of the field projection values that come out of this are still exactly the same as before, but it wouldn't hurt to have another pair of eyes on it.

[QimingFlex]

Hi @yaugenst-flex ,looks good to me, just a few questions regarding the surface current computation.