For those of us uninformed, what’s the difference between O and o?
In fact, he refers to Landau for the definition of little-o.
f(n) = o(g(n)) means as n increases, f(n)/g(n) must shrink
s/must shrink/must eventually shrink, after finitely many n/
Equivalently, must go to zero in the limit.
But you're not right in that the upper bound of that expression eventually stops decreasing, in fact for simple f and g as long as f is positive and eventually bounded by g the expression will decrease infinitely often if my intuition is correct
The big O notation is very often used to denote exact complexity of an algorithm even if the notation is technically an upper bound.
The little o notation is usually used to denote a small asymptotic improvement over some known complexity.
For example if some sublinear algorithm would have n^(7/8) complexity - would be probably advertised as big O of that. But n^(1-eps) is shared as o(n) with exact constant provided as a detail.
https://stackoverflow.com/questions/1364444/difference-betwe...
Lim f/g -> C a constant
Lim f/h -> 0This isn't quite correct. O(g) doesn't require the limit to exist.
If you were joking then maybe you got me
O(2n+1) = O(2n) = O(n)
o(2n+1) > o(2n) > o(n)
Both define upper boundary, but big O can read like "the function is generally proportional to ___" and little o can read like "the function is never more than _____"
Big O is sort of like <=. little o is sort of like <.
O(n) is: "there exists a K such that, for sufficiently large n, K*n is always larger".
o(n) is: "for every K, for sufficiently large n, K*n is always larger". (So o(2n+1) and o(2n) and o(n) are the same thing.)
For what it's worth you can leave out the 'sufficiently large n' part, assuming we're talking about positive integers (or continuous functions on the nonnegative reals). I like to leave it in though because it makes the jump to defining both o, O and Theta in terms of lim sup f/g a little easier.
I don't think any of those are right. The latter two are trivially equivalent, the former also is since it differs by a factor of at most 3 for all n >= 1.
I still think the simplest definition for o(f) is 'g in o(g) iff O(g) is a proper subset of O(f)'. Or you can just say g is dominated by f in the sense that lim sup g/f = 0.
I'm fairly sure those two are equivalent, but it's a good little exercise.