Progressively Interactive Evolutionary Multi-Objective Optimization ...

problems. The study discusses some of the intricate issues involved in
handling bilevel multi-objective optimization problems. A number of test
problems are also developed and a hybrid evolutionary-cum-local-search
technique is proposed to handle the problems. The proposed solution
methodology is made self adaptive such that the parameters of the algorithm
need not be supplied by the user. All the test problems are two
objective problems at both levels and the algorithm aims the entire front
which leads to high number of function evaluations. The approach is once
again a posteriori where decision making is performed after finding the
entire front. Once a generic algorithm for handling bilevel multi-objective
problem is available, in the next paper, it is augmented to interact with
a decision maker and seek for the most preferred solution instead of the
entire front.
1.7.5 Bilevel Multi-Objective Optimization Problem Solving Using
Progressively Interactive EMO
In the fifth paper [27] the hybrid bilevel evolutionary multi-objective optimization
algorithm has been extended to a progressively interactive algorithm
such that the decision maker is able to interact during the search
process and the most preferred solution could be obtained quickly and
with much higher accuracy. The progressively interactive approach using
the value function described in the first two papers is used in this algorithm
at the upper level which allows decision maker preferences to be
incorporated. Incorporating decision making at the upper level leads to
six to ten times savings in function evaluations for all the considered test
problems and is able to produce a solution much closer to the true solution.
The algorithm, however, accepts decision maker preferences only at
the upper level during the search process. Decision making at both levels
during the search process opens an interesting area for researchers to
pursue. Accepting preference information at both levels becomes a sophisticated
problem, as it could lead to a conflict; decision maker at one of the
levels should be given priority, or a mutually agreeable solution should be
searched. This scenario has not been studied and does not fall in the realm
of this dissertation.
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