factorial is a function that grows faster than any exponential but slower than n^n. we explore other functions in this category.
side note: if you have a bound "a" on the base, (a+delta)^n grows faster than a^n. the functions below are intended for dominating an exponential with unbounded but constant base.
a^n = exp(n * log a). n^n = exp(n * log n). we therefore explore exp(n * f(n)) where f(n) grows faster than a constant but slower than log n.
in decreasing rate of growth:
exp(n*(log(n) - a)) where a>0. this is similar to factorial by Stirling approximation. in Stirling, a=1 , and there is also a factor of sqrt(2pi*n).
exp(n*log(n)*a) where a<1
exp(n*(log(n))^a) where a<1
exp(n*(log(log(n))^a)) where a>1
exp(n*(log(log(n))*a)) where a>1
exp(n*(log(log(n))+a)) where a>0
exp(n*(log(log(n)+a))) where a is unrestricted
exp(n*(log(log(n))+a)) where a<0
exp(n*(log(log(n))*a)) where a<1
exp(n*(log(log(n))^a)) where a<1
although these functions grow faster than any exponential, they may overtake extremely slowly. for example, exp(n*(log(log(n))^0.5)) exceeds 10^n around n = exp(201) = 10^87 .
simplified version, seeking functions that grow faster than a constant but slower than g(x)=x .
x - a where a>0
x*a where a<1
x^a where a<1
log(x)^a where a>1
log(x)*a where a>1
log(x)+a where a>0
log(x+a) where a is unrestricted
log(x)+a where a<0
log(x)*a where a<1
log(x)^a where a<1
No comments :
Post a Comment