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求解一类时间分数阶扩散方程的深度学习方法

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偏微分方程可以用深度学习方法求解,其求解思路是构建损失函数、采集样本点,然后在采集到的时空样本点上利用随机梯度下降法训练神经网络,直接去逼近方程,从而把方程求解问题转化为极小化损失函数的问题。特别地,对时间分数阶扩散方程而言,损失函数刻画了神经网络与方程的分数阶算子、初值条件、边界条件等的逼近程度。常见的损失函数有均方误差损失函数及交叉熵误差函数。理论上,使损失函数减小到零的神经网络就是方程的解。本文证明,用深度学习方法求解时间分数阶扩散方程时均方误差损失函数可以减小到零,且相应的神经网络在解区域上一致收敛到方程的真解,因而此时的神经网络就是方程的解。数值算例验证了理论分析。
A deep learning method for the time-fractional diffusion equations
Under very general assumptions,standard feedforward neural networks can approximate any con-tinuous or discontinuous function as long as the number of hidden elements in the hidden layer is large enough.Particularly,when deep learning methods are used to solve differential equations,the idea is to build a loss function,collect sample points and use the stochastic gradient descent method to train the neural network to approximate the solution of equation directly on the collected sample points,thus transform the problem of solving equation into the optimization problem of minimizing loss function.When the time-fractional diffusion equations are solved by a deep learning method,the loss function measures the approximation degree be-tween the neural network and the fractional differential operator,initial value conditions,boundary condition,etc.Theoretically,the very neural network reducing the loss function to zero is a solution of equation.In this paper,we show that the loss function in the form of mean square error can reduce to zero and the correspond-ing neural network converges uniformly to the exact solution,that is,the neural network is a solution of equa-tion.Numerical examples verify the theoretical analysis.

Neural networkTime-fractional diffusion equationNumerical analysis

于雅新、冯民富

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四川大学数学学院,610064

神经网络 时间分数阶扩散方程 数值分析

国家自然科学基金

11971337

2024

四川大学学报(自然科学版)
四川大学

四川大学学报(自然科学版)

CSTPCD北大核心
影响因子:0.358
ISSN:0490-6756
年,卷(期):2024.61(4)
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