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In mathematics of stochastic systems, the Runge–Kutta method is a technique for the approximate numerical solution of a stochastic differential equation. It is a generalization of the Runge–Kutta method for ordinary differential equations to stochastic differential equations (SDEs). Importantly, the method does not involve knowing derivatives the coefficient functions in the SDEs. ==Most basic scheme== Consider the Itō diffusion satisfying the following Itō stochastic differential equation : with initial condition , where stands for the Wiener process, and suppose that we wish to solve this SDE on some interval of time . Then the basic Runge–Kutta approximation to the true solution is the Markov chain defined as follows:〔P. E. Kloeden and E. Platen. ''Numerical solution of stochastic differential equations'', volume 23 of Applications of Mathematics. Springer--Verlag, 1992.〕 * partition the interval into subintervals of width : : * set ; * recursively compute for by : where and The random variables are independent and identically distributed normal random variables with expected value zero and variance . This scheme has strong order 1, meaning that the approximation error of the actual solution at a fixed time scales with the time step . It has also weak order 1, meaning that the error on the statistics of the solution scales with the time step . See the references for complete and exact statements. The functions and can be time-varying without any complication. The method can be generalized to the case of several coupled equations; the principle is the same but the equations become longer. 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「Runge–Kutta method (SDE)」の詳細全文を読む スポンサード リンク
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