Genetic algorithm should choose a mutation operator by default

[abeham]

The mutation operator is an OptionalConstrainedValueParameter which by default is set to null, meaning no mutation operator is chosen. We know however that genetic algorithms usually work better with mutation.

Any user that creates a new GA, drops some problem to it and clicks run, essentially runs a bad configuration. I consider it a separate problem to chose the best mutation operator, but any mutation operator may be better than choosing no mutation.

[abeham]

The cleanest solution in my opinion would be to change the parameter type from OptionalConstrainedValueParameter<IManipulator> to ConstrainedValueParameter<IManipulator>. We do have the mutation probability parameter which, if set to 0%, can produce the same configuration compared to selecting no mutation operator. Of course this would break API backwards compatibility. (actually, the parameter was never exposed as an optional constrained value parameter, but as interface type)

Another option would be to check in OnProblemChanged if the user loads a problem for the first time and then select a mutation operator by default. This is a bit more tricky, because the user could deliberately change mutation to "-" in which case we must not overrule with a default choice.

[abeham]

r15006: changed mutator parameter from optional constrained value to constrained value

[abeham]

Shall we adapt the OS variants also? In OS mutation is not as important as it is for the standard GA. Nevertheless, the default configuration would be more consistent if in addition to the default 5% mutation probability, a mutation operator would also be selected.

[abeham]

r15007: adapted wiring code to be the same as with crossover, choosing the default manipulator intead of the first (by name)

[abeham]

r15008: small fix

[mkommend]

Pretty neat feature. Please adapt the OSGA as well!

[mkommend]

r15047: Adapted symbolic data analysis problems to use the MultiSymbolicExpressionTreeManipulator as default.

[abeham]

r15049:

• adapted OSGA, Island-GA, Island-OSGA, and SASEGASA as well
• added default crossover logic to SASEGASA

[abeham]

This should also be changed in ALPS

[mkommend]

Reviewed r15006, r15007, r15008, r15049.

[abeham]

r15070: adapted ALPS and ALPS-OS

Regarding r15047: looks good

[mkommend]

Reviewed r15070: looks fantastic.

[abeham]

r15107: also adapted NSGA-II

[mkommend]

Reviewed and tested r15107.

[mkommend]

r15238: Merged r15006:r15008, r15047, r15049, r15070, r15107 into stable.