Port SymbolicExpressionTree manipulation operators from 3.2 to 3.3

[gkronber]

r4189:

• Implemented manipulation operator for symbolic expression tree encoding that replaces one randomly chosen branch with a new randomly initialized branch.

[mkommend]

r8333: Added RemoveBranchManipulation to HL.Encodings.SymbolicExpressionTree.

[mkommend]

r8335: Adapted unit test to take new GP manipulator into account.

[mkommend]

r8342: Updated GP samples to contain the new manipulator.

[gkronber]

Interestingly the symbolic regression sample unit test became slower because of the new operator (from 1m43s to 2m11s)

[mkommend]

differences between GP samples with or without remove branch mutation

[mkommend]

Replying to gkronber:

Interestingly the symbolic regression sample unit test became slower because of the new operator (from 1m43s to 2m11s)

I have attached a file containing two runs of the GP sample; one time with the remove branch mutation and one time without and exactly the same seed as the unit test uses. Both result in the same quality values as the unit test does /did. When looking at the results it becomes obvious why the unit test became slower, because more nodes were evaluated. The sum of the average tree size per generation over all generations increases from 2655.662 to 3521.365.

[gkronber]

This is a reasonable explanation for the performance deterioration.

Reviewed the operator added with r8333 (especially like the recursive application to generate a minimal tree). Changesets r8335 and r8342 should be correct as well.