Automatic Regularization Selection

[shanemcq18]

Automatic regularization selection:

• New methods fit_regselect_continuous() and fit_regselect_discrete() in the ROM and ParametricROM classes.
• utils.gridsearch() implements grid search followed up by derivative-free log-scale optimization.
• Class method TikhonovSolver.get_operator_regularizer() to construct diagonal Tikhonov regularizers where each operator is regularized by a different scalar.

New transformers for custom shifting / scaling:

• pre.ShiftTransformer
• pre.ScaleTransformer
• pre.NullTransformer
• pre.TransformerPipeline

Small improvements:

• Executing individual test files now runs the tests contained within.
• utils.TimedBlock has a rebuffer attribute that, when set to True, prevents printing until the end of the block.
• Improved test coverage, fixed some documentation typos, etc.

Regularization selection is not demonstrated yet in tutorials.