Expression Evaluation By Cell-like Model

Membrane computing,inspired from the architecture and the functioning of biological cells, is a branch of biology computing. Membrane computing, also called P system was proposed by Romanian scientist Gheorghe Paun in 1998. Membrane computing not only brings new ideas and models for computer science, but also introduces a new modeling tool for natural systems. Arithmetic operation and expression evaluation are basic operations of a computing model, but researches on arithmetic operation and expression evaluation in membrane system are relatively weak.Based on cell-like model, this thesis primarily focuses on issues about arithmetic operations and the arithmetic of constructing expression's membrane. The thesis's major work is listed as follow:1) According to the basic principles and characteristics of membrane computing, this thesis designed P systems of arithmetic operation without priority, which well reflected the parallelism feature of membrane computing.2) The P systems of arithmetic operation without priority have many rules, and are difficult to understand. So this thesis gave another suit of the arithmetic operation P systems with priority and simpler rules, easier to understand, and have higher parallelism.3) Proposed an expression's membrane structure constructing algorithm based on the arithmetic operation P systems.4) Proposed an optimized expression's membrane structure constructing algorithm to improve the membrane structure's parallelism by changing the expression's computing method. The arithmetic expressions could be divided into a set of additions, subtractions, multiplications and divisions. These operations can be concurrently executed at a certain degree. Expression evaluation proposed in this thesis utilized this parallelism to improve efficiency and meanwhile made full use of membrane computing's feature of maximal parallelism.5) In the P systems of arithmetic operation, this thesis imported synchronization and mutex to ensure the correctness and parallelism of the computation.6) Simulated expression evaluation of membrane computing by computer, which verify the correctness and feasibility of the algorithm.Since been proposed by Gheorghe Paun, membrane computing rapidly becomes a hot research area. However, currency computer's implementation still has to rely on the implementation of the basic arithmetic operations and expression evaluation. This thesis's research is of important academic and practical significance to the realization of universal biological computer.