Friday, December 7, 2012

Asymptotic Notation

We sometime become concern about the asymptotic nature of a function specially when we are considering Limit or nature of a function or composite function at Neighbourhood(Nbd) of a point.

We use following definitions :-
Typically we use these notation for x → ∞.
(i) Big -O :-  f = O(g)  ∃ (xϵ) ∈ R2 s.t. ∀x ≥ x0  |f(x)| ≤ |ϵg(x)| 
This g actually represent a asymptotic upper bound of
For more stronger bound we have small-o which is described as :-
f(x) = o(g(x))   ϵ ∈ R   x∈ R s.t.  ∀x ≥ x0  |f(x)|  ≤ |ϵg(x)| . 

(ii) Big - Ω :-  f = O(g) ↔ g =  Ω(f). Similarly defined ω.
(iii) Big - Θ :-  f = Θ(g) ↔ g =  Θ(f) ↔ g =  O(f) . Similarly defined θ.

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