Abstract
•Granular convexity of interval type-2 fuzzy functions is defined.•Properties of granular convex interval type-2 fuzzy functions are investigated.•Two kinds of granular solutions are presented for interval type-2 fuzzy optimization.•Optimality conditions are established for interval type-2 fuzzy optimization.
Interval type-2 fuzzy optimization models have become increasingly attractive and useful in various practical applications. Nonetheless, there israre discussion on the optimality conditions of granular solutions for the problem of interval type-2 fuzzy optimization. In response to this, we introduce two kinds of granular solutions and endeavor to ascertain the conditions under which a feasible solution becomes granular-efficient in this study. Firstly, we put forth the concept of granular convexity for interval type-2 fuzzy functions, and investigate some fundamental properties. Secondly, we present the concepts of granular-efficient solutions and weakly granular-efficient solutions for optimization problems under an interval type-2 fuzzy setting. Finally,we obtain the optimality conditions for interval type-2 fuzzy optimization. Furthermore, several examples arepresented to demonstrate the proposed concepts and main results.