我最后得到的图像是这样的
,matlab编程,所有代码都是按照网上答案给出,参数设置也没有问题,求问到底是什么原因呢?刚刚接触深度学习,求各位大佬解答
附sparsityAutoencoderCost代码
function [cost,grad] = sparseAutoencoderCost(theta, visibleSize, hiddenSize, ...
lambda, sparsityParam, beta, data)
% visibleSize: the number of input units (probably 64)
% hiddenSize: the number of hidden units (probably 25)
% lambda: weight decay parameter
% sparsityParam: The desired average activation for the hidden units (denoted in the lecture
% notes by the greek alphabet rho, which looks like a lower-case "p").
% beta: weight of sparsity penalty term
% data: Our 64x10000 matrix containing the training data. So, data(:,i) is the i-th training example.
% The input theta is a vector (because minFunc expects the parameters to be a vector).
% We first convert theta to the (W1, W2, b1, b2) matrix/vector format, so that this
% follows the notation convention of the lecture notes.
W1 = reshape(theta(1:hiddenSize*visibleSize), hiddenSize, visibleSize);
W2 = reshape(theta(hiddenSize*visibleSize+1:2*hiddenSize*visibleSize), visibleSize, hiddenSize);
b1 = theta(2*hiddenSize*visibleSize+1:2*hiddenSize*visibleSize+hiddenSize);
b2 = theta(2*hiddenSize*visibleSize+hiddenSize+1:end);
% Cost and gradient variables (your code needs to compute these values).
% Here, we initialize them to zeros.
cost = 0;
W1grad = zeros(size(W1));
W2grad = zeros(size(W2));
b1grad = zeros(size(b1));
b2grad = zeros(size(b2));
%% ---------- YOUR CODE HERE --------------------------------------
% Instructions: Compute the cost/optimization objective J_sparse(W,b) for the Sparse Autoencoder,
% and the corresponding gradients W1grad, W2grad, b1grad, b2grad.
%
% W1grad, W2grad, b1grad and b2grad should be computed using backpropagation.
% Note that W1grad has the same dimensions as W1, b1grad has the same dimensions
% as b1, etc. Your code should set W1grad to be the partial derivative of J_sparse(W,b) with
% respect to W1. I.e., W1grad(i,j) should be the partial derivative of J_sparse(W,b)
% with respect to the input parameter W1(i,j). Thus, W1grad should be equal to the term
% [(1/m) \Delta W^{(1)} + \lambda W^{(1)}] in the last block of pseudo-code in Section 2.2
% of the lecture notes (and similarly for W2grad, b1grad, b2grad).
%
% Stated differently, if we were using batch gradient descent to optimize the parameters,
% the gradient descent update to W1 would be W1 := W1 - alpha * W1grad, and similarly for W2, b1, b2.
% forward propagation
data_size = size(data);
active_value2 = repmat(b1,1,data_size(2));
active_value3 = repmat(b2,1,data_size(2));
active_value2 = sigmoid(W1*data+active_value2); % the activation value of a2
active_value3 = sigmoid(W2*active_value2+active_value3); % the activation value of a3
% computing error term and cost
squared_error_term = sum(sum((active_value3-data).^2)./2)/data_size(2); % calculate the squared_error term
weight_decay = lambda/2*(sum(sum(W1.^2))+sum(sum(W2.^2))); % calculate the weight decay term
p_real = sum(active_value2,2)./data_size(2);
p_para = repmat(sparsityParam,hiddenSize,1);
sparsity_penalty = beta.*sum(p_para.*log(p_para./p_real)+(1-p_para).*log((1-p_para)./(1-p_real))); % calculate the sparsity penalty term
cost = squared_error_term + weight_decay + sparsity_penalty;
delta3 = (active_value3-data).*(active_value3).*(1-active_value3);
average_sparsity = repmat(sum(active_value2,2)./data_size(2),1,data_size(2));
default_sparsity = repmat(sparsityParam,hiddenSize,data_size(2));
sparsity_penalty = beta.*(-(default_sparsity./average_sparsity)+((1-default_sparsity)./(1-average_sparsity)));
delta2 = (W2'*delta3+sparsity_penalty).*((active_value2).*(1-active_value2));
% backword propagation
W2grad = delta3*active_value2'./data_size(2)+lambda.*W2;
W1grad = delta2*data'./data_size(2)+lambda.*W1;
b2grad = sum(delta3,2)./data_size(2);
b1grad = sum(delta2,2)./data_size(2);
%-------------------------------------------------------------------
% After computing the cost and gradient, we will convert the gradients back
% to a vector format (suitable for minFunc). Specifically, we will unroll
% your gradient matrices into a vector.
grad = [W1grad(:) ; W2grad(:) ; b1grad(:) ; b2grad(:)];
end
%-------------------------------------------------------------------
% Here's an implementation of the sigmoid function, which you may find useful
% in your computation of the costs and the gradients. This inputs a (row or
% column) vector (say (z1, z2, z3)) and returns (f(z1), f(z2), f(z3)).
function sigm = sigmoid(x)
sigm = 1 ./ (1 + exp(-x));
end