API: move 'interp' out of spaces

[kohr-h]

In the hope of getting it merged faster, I created this PR that takes the minimal action to remove 'interp' from the spaces (where I no longer think it makes sense) to corresponding operators.

Tests will follow.

Please review this version.

[pep8speaks]

Checking updated PR...

No PEP8 issues.

Comment last updated at 2020-01-21 22:12:09 UTC

[kohr-h]

Some additional context: Apparently the PR #1459 is too big to review, so I'm trying to break it down into smaller ones. This one is only concerned with moving the interp property from spaces to operators and functions that make use of it (really only a few).
This implies that all calls to <space or element>.sampling(...) and <space or element>.interpolation(...) have to be replaced by according function calls. These functions are pulled out of the FunctionSpaceMapping type operators, which were removed.

I haven't adapted the tests yet since that would mean moving a bunch of code around, blowing up the size of the changes substantially. That'll come as a second step.

[aringh]

Review of the first 7 files, out of 11. So far I think it looks ok, but I don't think I have not understood all details. Detailed comments below.

I will try to review the rest shortly.

[aringh]

I have no strong opinion on whether interpolation should be an operator or not. This looks overall fine to me.

Ps. The remaining part was shorter than I though. So I reviewed it right away 😄 Ds.

[kohr-h]

Thanks for the partial review, @aringh. I'll try to get the changes done asap.

[kohr-h]

Doctests now work again and make more sense, sorry for the noise. I'll do the unit tests next.

[kohr-h]

It's been a while. Tests are fixed now, with only minor adaptions. Ready for final review.

Changes since last review:

• Nearest neighbor variants removed. Never used, and resulted in flaky tests.
• Fix added for a PyTest issue when one of the parameters is a NumPy array. PyTest caches test parameters and uses == to check if it has seen a value already. That doesn't work for arrays.
  Caching is only used for scope='module' or higher, so the default scope still works.

[aringh]

Partial review. Review of:

• examples/deform/linearized_fixed_template.py
• odl/contrib/datasets/ct/mayo.py
• odl/deform/linearized.py
• odl/discr/init.py
• odl/discr/discr_ops.py
• odl/discr/discr_utils.py

Will try to continue with the rest later this week.

[aringh]

Over all looks good to me!

[kohr-h]

Thanks for the review, @aringh! Remaining stuff is fixed, will merge after CI.