In several papers I have read that Bit-parallel pattern matching is an NFA-simulation.
My questions are:
1- Is it true in general? Or, is there any restrictions?
2- As any regular expression can be converted to NFA, how Bit-parallelism is able to handle some regex like: a?5
Update: Bit-parallel pattern matching is a family of well-known pattern matching algorithms in the literature of hardware-based pattern matching. It was introduced by Baeza-Yates and Gonnet (A New Approach to Text Searching, Communications of the ACM, 35(10):74–82, 1992; PDF) and has gained more attention recently, for example in Faro and Lecroq, Twenty Years of Bit-Parallelism in String Matching (Festschrift for Bořivoj Melichar, pp. 72–101; PDF).
In these papers there are several statements like: "Bit-parallelism is indeed particularly suitable for the eefficient simulation of non-deterministic automata.", second reference, page 2.