Results of MultiEncodingOperators are not stable / reproducable

[HeuristicLab-Trac-Bot]

Issue migrated from trac ticket # 3144

milestone: HeuristicLab 3.3.17 | component: Optimization | priority: high

2021-12-17 13:45:01: @mkommend created the issue

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If an algorithm uses a MultiEncoding for representing individuals and hence the respective MultiEncodingOperators, the results could vary although the random seed is fixed and a SequentialEngine for the algorithm execution is used.

[HeuristicLab-Trac-Bot]

2021-12-17 13:45:15: @mkommend changed status from new to accepted

[HeuristicLab-Trac-Bot]

2021-12-17 13:45:15: @mkommend edited the issue description

[HeuristicLab-Trac-Bot]

2021-12-17 14:12:36: @mkommend commented

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After bug hunting for several hours, we discovered that MultiEncodingOperators have dedicated operators saved in a separate parameter for each individual part of the MultiEncoding. This parameters are iterated and a new operation is spawned for parameter / operator that is executed on the part of the encoding.

The issue now is that parameters are internally saved within a dictionary. Iteration over an dictionary does not guarantee the same order, hence the execution order of the spawned operations differs and in turn the algorithm produces different results.

[HeuristicLab-Trac-Bot]

2021-12-17 15:08:30: @mkommend changed status from accepted to reviewing

[HeuristicLab-Trac-Bot]

2021-12-17 15:08:30: @mkommend changed owner from @mkommend to @abeham

[HeuristicLab-Trac-Bot]

2021-12-17 15:08:30: @mkommend commented

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r18153: Ordered discovered parameters of MultiEncodingOperator before operation creation.