Hybrid electromagnetism-like mechanism and migration strategy (EM-MS) algorithm is a recently developed optimization method which tries to benefit from both electromagnetism-like mechanism (EM) algorithm and migration strategy (MS).
IntroductionAttaining optimum designs for structures has been in the focus of wide attention over past years and has established its position as one of the main optimization problems in structural engineering domain. However it is very widely believed that, for many structures with the large number of elements, searching optimum designs is very extreme hardness and sometimes completely time consuming procedure. Hence, extensive studies have been carried out to develop different optimization methods, ranging from gradient-based search techniques to derivative-free global optimization algorithms. As an alternative to the classical optimization approaches, meta-heuristic optimization techniques such as harmony search (HS) [7] have been widely utilized and improved to solve structural optimization problems characterized by non-convex, dis-continuous, and non-differentiable [8][9][10][11][12][13][14][15][16].The meta-heuristic algorithms have some advantages such as a simple framework and ease of implementation. Therefore, these algorithms have been adopted by researchers so far and are well suited to solve various structural optimum design problems including the sizing, layout, and topology optimization problems [17][18][19][20][21]. Due to probabilistic nature of the meta-heuristics, they do not guarantee finding global optimum solutions for any kind of the problems. However, if they properly implemented, meta-heuristics can provide near-optimal or optimal solutions with higher qualities. In designing efficient meta-heuristic algorithms, the exploration and exploitation are extremely important mechanisms. The exploration mechanism is related to the ability of exploring many and different regions of the search space, while the exploitation mechanism is related to the reduction of the diversity by focusing on the individuals with higher fitness to obtain high quality solutions. Therefore, the adequate balance between the exploration and exploitation mechanisms is a vital issue for these algorithms to be effectively executed. To this end, numerous standard and hybrid meta-heuristic algorithms have been applied and developed to optimum design of structures. Some of them will be mentioned below.