Sparse partials for ExecComps

[kanekosh]

Purpose

I added has_diag_partials=True for the ExecComps with vector inputs and outputs. This tells OpenMDAO that those components have sparse diagonal partials. This should (slightly) reduce the runtime by eliminating the OM's automatic Jacobian coloring computations.

Type of change

• Refactoring (no functional changes, no API changes)

Testing

Checklist

Put an x in the boxes that apply.

• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6fc0a1c) 79.95% compared to head (d4e2a58) 79.95%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #63   +/-   ##
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  Coverage   79.95%   79.95%           
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  Files          85       85           
  Lines        9300     9300           
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  Hits         7436     7436           
  Misses       1864     1864           

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[eytanadler]

When has_diag_partials is set to True, does OpenMDAO perturb all elements in a given vectorized input simultaneously when computing the complex step derivatives? Many of these components can be replaced with OpenConcept's ElementMultiplyDivideComp, which might be even better. You have a better sense than I do of the times for coloring vs. actually computing derivatives.

[kanekosh]

When has_diag_partials is set to True, does OpenMDAO perturb all elements in a given vectorized input simultaneously when computing the complex step derivatives?

Yes, that's what OM does (reference). ElementMultiplyDivideComp would be slightly better but I guess the speedup is minimal because that's just one additional compute evaluation with complex numbers in ExecComp.

[eytanadler]

Gotcha, this looks good then. The Python 3.8 flake8 test is no longer run because of mdolab/.github#64, which was merged yesterday. I've updated the required tests in the OpenConcept repo to reflect this. I'll try rerunning the tests and see if they update, but if not I guess I can just override the tests and merge it.