Systolic trellis automata: Stability, decidability and complexity

Systolic trellis automata are models of hexagonally connected and triangularly shaped systolic arrays. This paper studies the problems of stability, decidability, and complexity for them. The original definition of systolic trellis automata requires that an input string is fed to a specific row of processors. Here it is shown that given a homogeneous trellis automaton we can construct an equivalent one (stable or superstable) which allows to feed the input string to any sufficiently long row of processors. Moreover, some closure and decidability results for trellis automata are established and the computational complexity of languages accepted by trellis automata is investigated.