In simple exponentiation A^B , the fast calculation consists of writing B in the binary base , B = B0 + 2 B1+ ( 2^2)B2 + …+ (2^d) Bd
So A^B can be written (A^B0) (A^2B1)… (A^(2^d)Bd) , so the number of operation is comparable with d so with Ln(B).
Tetration is written tetA(B) = A^A^A^A^A…. B times.
So the question is there is fast calculation for tetration ?