#1886 added fix within processed variable

[Scottmar93]

Description

During the solver setup, the list of inputs/sensitivities is sorted by string and then used to assign elements of the y-array to each sensitivity. This applies the same sorting of the list before extracting the sensitivities during the process variables stage.

I haven't added a test because I couldn't think of a good way without having a full integration test (passing a full model through the pipeline and then checking that the sensitivities are independent of the order of the inputs dictionary). However, I can add it if you think this is worth it for this.

Fixes #1886

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ flake8
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

Merging #1894 (2396ed3) into develop (751c18d) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #1894   +/-   ##
========================================
  Coverage    99.28%   99.28%           
========================================
  Files          345      345           
  Lines        19116    19119    +3     
========================================
+ Hits         18980    18983    +3     
  Misses         136      136           

Impacted Files	Coverage Δ
pybamm/solvers/base_solver.py	99.35% <100.00%> (+<0.01%)	⬆️
pybamm/solvers/processed_variable.py	99.68% <100.00%> (ø)

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[valentinsulzer]

Thanks @Scottmar93 . I checked changing the order in this test and indeed it fails, so it only used to work because p,q,r,s is already sorted. Could you change the order of the sensitivities in the test to make sure it still works with your fix?

[Scottmar93]

@tinosulzer ah nice!! Yeah will do!

[Scottmar93]

Okay, the original fix passed for some variables but not all so I have just changed it so that the inputs dictionary is sorted straight away upon being passed to the solver. This now passes the test with the dictionary keys in a different order.

[martinjrobins]

thanks @Scottmar93 , this looks good, getting some strange errors in python 3.8 and 3.9 on ubuntu. I was unable to replicate this on my machine (ubuntu, python 3.8).

[valentinsulzer]

I think the test error is unrelated, so happy to merge this

[Scottmar93]

I've tried merging from develop so hopefully that solves the testing issue. It looked like something that was failing on other branches as well though.