The standard procedure to transform a regular expression of size n
to an ϵ-free nondeterministic finite automaton yields automata
with O(n) states and O(n2) transitions. For a long time this
was supposed to be also the lower bound, but a result by
Hromkovic et al. showed how to build an ϵ-free NFA with
only O(n log2(n)) transitions. The current lower bound on the
number of transitions is Ω(n log(n)). A rough running time estimation for the common
follow sets (CFS) construction proposed by Hromkovič
et al. yields a cubic algorithm. In this paper we present a
sequential algorithm for the CFS construction which works in time
O(n log(n) + size of the output). On a CREW PRAM the CFS
construction can be performed in time O(log(n)) using O(n + (size of the output)/log(n)) processors. We also present a
simpler proof of the lower bound on the number of transitions.