P systems withd-division are a particular class of distributed and parallel computing models investigated in membrane computing, which are inspired from the budding behavior of Baker’s yeast (a cell can generate several cells in one reproducing cycle). In previous works, such systems can theoretically generate exponential working space in linear time and thus provide a way to solve computational hard problems in polynomial time by a space-time tradeoff, where the precise execution time of each evolution rule, one time unit, plays a crucial role. However, the restriction that each rule has a precise same execution time does not coincide with the biological fact, since the execution time of biochemical reactions can vary because of external uncontrollable conditions. In this work, we consider timed P systems withd-division by adding a time mapping to the rules to specify the execution time for each rule, as well as the efficiency of the systems. As a result, a time-free solution to Hamiltonian path problem (HPP) is obtained by a family of such systems (constructed in a uniform way), that is, the execution time of the rules (specified by different time mappings) has no influence on the correctness of the solution.

Abstract:Tissue P systems are a class of distributed and parallel computing models investigated in membrane computing, which are inspired from the structure and functioning of communication cells in tissues. Such systems with cell division (corresponding to the mitosis behavior of living cells) can theoretically generate exponential working space in linear time, therefore providing a possible way to solve computational hard problems in feasible time by a space-time trade-off. In this work, we construct a family of tissue P systems with cell division to solve the vertex cover problems, and achieve a linear time solution (with respect to the size of the problems). Furthermore, we prove that the systems are constructed in a uniform manner and work in a confluent way.

Abstract:The dominating set problem is a well known NP hard problem. It means that as the instance size grows, they quickly become impossible to solve on traditional digital computers. Tile assembly model has been demonstrated as a highly distributed parallel model of computation. Algorithmic tile assembly has been proved to be Turing-universal. This paper proposes a tile assembly system for the dominating set problem. It only needs Θ (mn) tile types to solve such a complex problem in the time Θ (m + n) where n and m are the number of vertices and edges of the given graph, respectively.