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Rule 184 is a one-dimensional binary cellular automaton rule, notable for solving the majority problem as well as for its ability to simultaneously describe several, seemingly quite different, particle systems: * Rule 184 can be used as a simple model for traffic flow in a single lane of a highway, and forms the basis for many cellular automaton models of traffic flow with greater sophistication. In this model, particles (representing vehicles) move in a single direction, stopping and starting depending on the cars in front of them. The number of particles remains unchanged throughout the simulation. Because of this application, Rule 184 is sometimes called the "traffic rule".〔E.g. see Fukś (1997).〕 * Rule 184 also models a form of deposition of particles onto an irregular surface, in which each local minimum of the surface is filled with a particle in each step. At each step of the simulation, the number of particles increases. Once placed, a particle never moves. * Rule 184 can be understood in terms of ballistic annihilation, a system of particles moving both leftwards and rightwards through a one-dimensional medium. When two such particles collide, they annihilate each other, so that at each step the number of particles remains unchanged or decreases. The apparent contradiction between these descriptions is resolved by different ways of associating features of the automaton's state with particles. The name of the rule is a Wolfram code that defines the evolution of its states. The earliest research on Rule 184 seems to be the papers by Li (1987) and Krug and Spohn (1988). In particular, Krug and Spohn already describe all three types of particle system modeled by Rule 184.〔One can find many later papers that, when mentioning Rule 184, cite the early papers of Stephen Wolfram. However, Wolfram's papers consider only automata that are symmetric under left-right reversal, and therefore do not describe Rule 184.〕 ==Definition== A state of the Rule 184 automaton consists of a one-dimensional array of cells, each containing a binary value (0 or 1). In each step of its evolution, the Rule 184 automaton applies the following rule to each of the cells in the array, simultaneously for all cells, to determine the new state of the cell: An entry in this table defines the new state of each cell as a function of the previous state and the previous values of the neighboring cells on either side. The name for this rule, Rule 184, is the Wolfram code describing the state table above: the bottom row of the table, 10111000, when viewed as a binary number, is equal to the decimal number 184. The rule set for Rule 184 may also be described intuitively, in several different ways: *At each step, whenever there exists in the current state a 1 immediately followed by a 0, these two symbols swap places. Based on this description, Krug and Spohn (1984) call Rule 184 a deterministic version of a "kinetic Ising model with asymmetric spin-exchange dynamics". *At each step, if a cell with value 1 has a cell with value 0 immediately to its right, the 1 moves rightwards leaving a 0 behind. A 1 with another 1 to its right remains in place, while a 0 that does not have a 1 to its left stays a 0. This description is most apt for the application to traffic flow modeling. *If a cell has state 0, its new state is taken from the cell to its left. Otherwise, its new state is taken from the cell to its right. That is, each cell can be implemented by a multiplexer, and is closely related in its operation to a Fredkin gate.〔Li (1992). Li used this interpretation as part of a generalization of Rule 184 to nonlocal neighborhood structures.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「rule 184」の詳細全文を読む スポンサード リンク
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