Can this code be rearranged to run successfully

Question

MINATI PATRA 2024-2-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2087338-can-this-code-be-rearranged-to-run-successfully

回答： Jaimin 2024-8-9，11:03

% I got the following code from: https://in.mathworks.com/help/deeplearning/ug/solve-partial-differential-equations-using-deep-learning.html
% want to rearrange and run
numBoundaryConditionPoints = [25 25];
x0BC1 = -1*ones(1,numBoundaryConditionPoints(1));  x0BC2 = ones(1,numBoundaryConditionPoints(2));
t0BC1 = linspace(0,1,numBoundaryConditionPoints(1)); t0BC2 = linspace(0,1,numBoundaryConditionPoints(2));
u0BC1 = zeros(1,numBoundaryConditionPoints(1)); u0BC2 = zeros(1,numBoundaryConditionPoints(2));
numInitialConditionPoints  = 50;
x0IC = linspace(-1,1,numInitialConditionPoints); t0IC = zeros(1,numInitialConditionPoints);
u0IC = - sin(pi*x0IC);
X0 = [x0IC x0BC1 x0BC2]; T0 = [t0IC t0BC1 t0BC2]; U0 = [u0IC u0BC1 u0BC2];
numInternalCollocationPoints = 10000;
pointSet = sobolset(2); points = net(pointSet,numInternalCollocationPoints);
dataX = 2*points(:,1)-1;  dataT = points(:,2); ds = arrayDatastore([dataX dataT]);
numLayers = 9;  numNeurons = 20;
parameters = struct;
sz = [numNeurons 2];
parameters.fc1.Weights = initializeHe(sz,2);
'initializeHe' is used in Solve Partial Differential Equations Using Deep Learning.
parameters.fc1.Bias = initializeZeros([numNeurons 1]);
for layerNumber=2:numLayers-1
    name = "fc"+layerNumber;
    sz = [numNeurons numNeurons];
    numIn = numNeurons;
    parameters.(name).Weights = initializeHe(sz,numIn);
    parameters.(name).Bias = initializeZeros([numNeurons 1]);
end
sz = [1 numNeurons];  numIn = numNeurons;
parameters.("fc" + numLayers).Weights = initializeHe(sz,numIn);
parameters.("fc" + numLayers).Bias = initializeZeros([1 1]);
parameters
parameters.fc1
numEpochs = 3000; miniBatchSize = 1000; executionEnvironment = "auto";
initialLearnRate = 0.01; decayRate = 0.005;
mbq = minibatchqueue(ds, MiniBatchSize=miniBatchSize, MiniBatchFormat="BC", OutputEnvironment=executionEnvironment);
X0 = dlarray(X0,"CB"); T0 = dlarray(T0,"CB"); U0 = dlarray(U0);
if (executionEnvironment == "auto" && canUseGPU) || (executionEnvironment == "gpu")
    X0 = gpuArray(X0); T0 = gpuArray(T0); U0 = gpuArray(U0);
end
averageGrad = [];  averageSqGrad = [];
accfun = dlaccelerate(@modelLoss);
figure(1), C = colororder; lineLoss = animatedline(Color=C(2,:));
ylim([0 inf]),xlabel("Iteration"),ylabel("Loss"),grid on
start = tic; iteration = 0;
for epoch = 1:numEpochs
    reset(mbq);
    while hasdata(mbq)
        iteration = iteration + 1;
        XT = next(mbq);   X = XT(1,:); T = XT(2,:);
        % Evaluate the model loss and gradients using dlfeval and the modelLoss function.
        [loss,gradients] = dlfeval(accfun,parameters,X,T,X0,T0,U0);
        % Update learning rate.
        learningRate = initialLearnRate / (1+decayRate*iteration);
        % Update the network parameters using the adamupdate function.
        [parameters,averageGrad,averageSqGrad] = adamupdate(parameters,gradients,averageGrad, ...
            averageSqGrad,iteration,learningRate);
    end
    % Plot training progress.
    loss = double(gather(extractdata(loss)));
    addpoints(lineLoss,iteration, loss);
    D = duration(0,0,toc(start),Format="hh:mm:ss");
    title("Epoch: " + epoch + ", Elapsed: " + string(D) + ", Loss: " + loss)
    drawnow
end
accfun
tTest = [0.25 0.5 0.75 1];
numPredictions = 1001;
XTest = linspace(-1,1,numPredictions);
figure
for i=1:numel(tTest)
    t = tTest(i);
    TTest = t*ones(1,numPredictions);
    % Make predictions.
    XTest = dlarray(XTest,"CB");
    TTest = dlarray(TTest,"CB");
    UPred = model(parameters,XTest,TTest);
    % Calculate true values.
    UTest = solveBurgers(extractdata(XTest),t,0.01/pi);
    % Calculate error.
    err = norm(extractdata(UPred) - UTest) / norm(UTest);
    % Plot predictions.
    subplot(2,2,i)
    plot(XTest,extractdata(UPred),"-",LineWidth=2);
    ylim([-1.1, 1.1])
    % Plot true values.
    hold on
    plot(XTest, UTest, "--",LineWidth=2)
    hold off
    title("t = " + t + ", Error = " + gather(err));
end
subplot(2,2,2)
legend("Predicted","True")
%%%         Solve Burger's Equation Function
function U = solveBurgers(X,t,nu)
% Define functions.
f = @(y) exp(-cos(pi*y)/(2*pi*nu));
g = @(y) exp(-(y.^2)/(4*nu*t));
% Initialize solutions.
U = zeros(size(X));
% Loop over x values.
for i = 1:numel(X)
    x = X(i);
    % Calculate the solutions using the integral function. The boundary
    % conditions in x = -1 and x = 1 are known, so leave 0 as they are
    % given by initialization of U.
    if abs(x) ~= 1
        fun = @(eta) sin(pi*(x-eta)) .* f(x-eta) .* g(eta);
        uxt = -integral(fun,-inf,inf);
        fun = @(eta) f(x-eta) .* g(eta);
        U(i) = uxt / integral(fun,-inf,inf);
    end
end
end
%%% Model Loss Function
function [loss,gradients] = modelLoss(parameters,X,T,X0,T0,U0)
% Make predictions with the initial conditions.
U = model(parameters,X,T);
% Calculate derivatives with respect to X and T.
gradientsU = dlgradient(sum(U,"all"),{X,T},EnableHigherDerivatives=true);
Ux = gradientsU{1};
Ut = gradientsU{2};
% Calculate second-order derivatives with respect to X.
Uxx = dlgradient(sum(Ux,"all"),X,EnableHigherDerivatives=true);
% Calculate lossF. Enforce Burger's equation.
f = Ut + U.*Ux - (0.01./pi).*Uxx;
zeroTarget = zeros(size(f), "like", f);
lossF = mse(f, zeroTarget);
% Calculate lossU. Enforce initial and boundary conditions.
U0Pred = model(parameters,X0,T0);
lossU = mse(U0Pred, U0);
% Combine losses.
loss = lossF + lossU;
% Calculate gradients with respect to the learnable parameters.
gradients = dlgradient(loss,parameters);
end
%%% Model Function
function U = model(parameters,X,T)
XT = [X;T];
numLayers = numel(fieldnames(parameters));
% First fully connect operation.
weights = parameters.fc1.Weights;
bias = parameters.fc1.Bias;
U = fullyconnect(XT,weights,bias);
% tanh and fully connect operations for remaining layers.
for i=2:numLayers
    name = "fc" + i;
    U = tanh(U);
    weights = parameters.(name).Weights;
    bias = parameters.(name).Bias;
    U = fullyconnect(U, weights, bias);
end
end