“…A considerable amount of research has gone into devising improved algorithms for checking the satisfiability of various circuit models up to depth o(log n/ log log n) (see, for example, [26,35,30,29,36,5,21,27,18,40,19,6,20,9,25]), although the question of improved algorithms for checking the satisfiability of linear size bounded depth threshold circuits is still unresolved. The improvements range from superpolynomial factors to exponential factors depending on the circuit model, size and depth.…”