【讀書1】【2017】MATLAB與深度學習——示例:MNIST(2)
函式MnistConv使用反向傳播演算法訓練網路,獲取神經網路的權重和訓練資料,並返回訓練後的權重。
The function MnistConv, which trains thenetwork using the back-propagation algorithm, takes the neural network’sweights and training data and returns the trained weights.
[W1,W5, Wo] = MnistConv(W1, W5, Wo, X, D)
其中,W1、W5和Wo分別是卷積濾波器矩陣、池化-隱藏層權重矩陣和隱藏-輸出層權重矩陣。
where W1, W5, and Wo are the convolutionfilter matrix, pooling-hidden layer weight matrix, and hidden-output layerweight matrix, respectively.
X和D分別是訓練資料的輸入和正確輸出。
X and D are the input and correct outputfrom the training data, respectively.
下面的清單顯示了MnistConv.m檔案中的程式碼,它實現了MnistConv函式的功能。
The following listing shows the MnistConv.mfile, which implements the MnistConv function.
function [W1, W5, Wo] = MnistConv(W1, W5,Wo, X, D)
alpha = 0.01;
beta = 0.95;
momentum1 = zeros(size(W1));
momentum5 = zeros(size(W5));
momentumo = zeros(size(Wo));
N = length(D);
bsize = 100;
blist = 1:bsize:(N-bsize+1);
% One epoch loop 按照時代進行迴圈
for batch = 1:length(blist)
dW1= zeros(size(W1)); dW5= zeros(size(W5)); dWo= zeros(size(Wo)); %Mini-batch loop begin= blist(batch); fork = begin:begin+bsize-1 %Forward pass = inference x= X(:, :, k); % Input, 28x28 y1 = Conv(x, W1); % Convolution,20x20x20 y2 = ReLU(y1); % y3 = Pool(y2); % Pool, 10x10x20 y4 = reshape(y3, [], 1); % 2000 v5 = W5*y4; % ReLU, 360 y5 = ReLU(v5); % v = Wo*y5; % Softmax, 10 y= Softmax(v); % %One-hot encoding d= zeros(10, 1); d(sub2ind(size(d),D(k), 1)) = 1; % Backpropagation 反向傳播 e = d - y; % Output layer delta = e; e5= Wo' * delta; % Hidden(ReLU) layer delta5= (y5 > 0) .* e5; e4= W5' * delta5; % Pooling layer e3 = reshape(e4, size(y3)); e2= zeros(size(y2)); W3= ones(size(y2)) / (2*2); forc = 1:20 e2(:, :, c) = kron(e3(:, :,c), ones([2 2])) .* W3(:, :, c); end delta2= (y2 > 0) .* e2; % ReLU layer delta1_x= zeros(size(W1)); % Convolutional layer forc = 1:20 delta1_x(:,:, c) = conv2(x(:, :), rot90(delta2(:, :, c), 2), 'valid'); end dW1= dW1 + delta1_x; dW5= dW5 + delta5*y4'; dWo= dWo + delta *y5'; end %Update weights 更新權值 dW1= dW1 / bsize; dW5= dW5 / bsize; dWo= dWo / bsize; momentum1= alpha*dW1 + beta*momentum1; W1= W1 + momentum1; momentum5= alpha*dW5 + beta*momentum5; W5= W5 + momentum5; momentumo= alpha*dWo + beta*momentumo; Wo= Wo + momentumo;
end
end % 函式結束的end標記
這個程式碼看起來比以前的例子要複雜得多。
This code appears to be rather more complexthan the previous examples.
讓我們一部分一部分地看看這段程式碼。
Let’s take a look at it part by part.
函式MnistConv通過小批量方法訓練網路,而前面的示例使用SGD和批量方法。
The function MnistConv trains the networkvia the minibatch method, while the previous examples employed the SGD andbatch methods.
——本文譯自Phil Kim所著的《Matlab Deep Learning》
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