Online Premeans and Their Computation Complexity
AbstractWe extend some approach to the family of symmetric means (i.e. symmetric functions $$\mathscr {M} :\bigcup _{n=1}^\infty I^n \rightarrow I$$ M : ⋃ n = 1 ∞ I n → I with $$\min \le \mathscr {M}\le \max $$ min ≤ M ≤ max ; I is an interval). Namely, it is known that every symmetric mean can be written in a form $$\mathscr {M}(v_1,\dots ,v_n):=F(f(v_1)+\cdots +f(v_n))$$ M ( v 1 , ⋯ , v n ) : = F ( f ( v 1 ) + ⋯ + f ( v n ) ) , where $$f :I \rightarrow G$$ f : I → G and $$F :G \rightarrow I$$ F : G → I (G is a commutative semigroup). For $$G=\mathbb {R}^k$$ G = R k or $$G=\mathbb {R}^k \times \mathbb {Z}$$ G = R k × Z ($$k \in \mathbb {N}$$ k ∈ N ) and continuous functions f and F we obtain two series of families (depending on k). It can be treated as a measure of complexity in a family of means (this idea is inspired by theory of regular languages and algorithmics). As a result we characterize the celebrated families of quasi-arithmetic means ($$G=\mathbb {R}\times \mathbb {Z}$$ G = R × Z ) and Bajraktarević means ($$G=\mathbb {R}^2$$ G = R 2 under some additional assumptions). Moreover, we establish certain estimations of complexity for several other classical families.
