UFLDL Exercise: Convolution and Pooling

这是UFLDL Convolution and Pooling的练习题代码。

在以往练习的基础上填写cnnConvolve.m / cnnPool.m / cnnExercise.m

cnnConvolve.m

function convolvedFeatures = cnnConvolve(patchDim, numFeatures, images, W, b, ZCAWhite, meanPatch)%cnnConvolve Returns the convolution of the features given by W and b with%the given images%% Parameters:%  patchDim - patch (feature) dimension%  numFeatures - number of features%  images - large images to convolve with, matrix in the form%           images(r, c, channel, image number)%  W, b - W, b for features from the sparse autoencoder%  ZCAWhite, meanPatch - ZCAWhitening and meanPatch matrices used for%                        preprocessing%% Returns:%  convolvedFeatures - matrix of convolved features in the form%                      convolvedFeatures(featureNum, imageNum, imageRow, imageCol)numImages = size(images, 4);imageDim = size(images, 1);imageChannels = size(images, 3);%convolvedFeatures = zeros(numFeatures, numImages, imageDim - patchDim + 1, imageDim - patchDim + 1);% Instructions:%   Convolve every feature with every large image here to produce the %   numFeatures x numImages x (imageDim - patchDim + 1) x (imageDim - patchDim + 1) %   matrix convolvedFeatures, such that %   convolvedFeatures(featureNum, imageNum, imageRow, imageCol) is the%   value of the convolved featureNum feature for the imageNum image over%   the region (imageRow, imageCol) to (imageRow + patchDim - 1, imageCol + patchDim - 1)%% Expected running times: %   Convolving with 100 images should take less than 3 minutes %   Convolving with 5000 images should take around an hour%   (So to save time when testing, you should convolve with less images, as%   described earlier)% -------------------- YOUR CODE HERE --------------------% Precompute the matrices that will be used during the convolution. Recall% that you need to take into account the whitening and mean subtraction% stepsWT = W * ZCAWhite; %在线性解码器一节的练习中，最后对W进行可视化时也右乘了ZCAWhitebias = b - WT * meanPatch;% --------------------------------------------------------convolvedFeatures = zeros(numFeatures, numImages, imageDim - patchDim + 1, imageDim - patchDim + 1);for imageNum = 1:numImages  for featureNum = 1:numFeatures    % convolution of image with feature matrix for each channel    convolvedImage = zeros(imageDim - patchDim + 1, imageDim - patchDim + 1);    for channel = 1:imageChannels      % Obtain the feature (patchDim x patchDim) needed during the convolution      % ---- YOUR CODE HERE ----      %feature = zeros(8,8); % You should replace this      patchSize = patchDim *patchDim;      feature = reshape(WT(featureNum,1+patchSize*(channel-1):patchSize*channel),patchDim, patchDim);            % ------------------------      % Flip the feature matrix because of the definition of convolution, as explained later      feature = rot90(squeeze(feature),2);            % Obtain the image      im = squeeze(images(:, :, channel, imageNum));      % Convolve "feature" with "im", adding the result to convolvedImage      % be sure to do a 'valid' convolution      % ---- YOUR CODE HERE ----            convolvedImage = convolvedImage + conv2(im, feature, 'valid');%所有通道的卷积结果相加                  % ------------------------    end        % Subtract the bias unit (correcting for the mean subtraction as well)    % Then, apply the sigmoid function to get the hidden activation    % ---- YOUR CODE HERE ----        convolvedImage = sigmoid(convolvedImage + bias(featureNum));    % ------------------------        % The convolved feature is the sum of the convolved values for all channels    convolvedFeatures(featureNum, imageNum, :, :) = convolvedImage;  endendendfunction sigm = sigmoid(x)      sigm = 1 ./ (1 + exp(-x));end

cnnPool.m【参考了http://blog.csdn.net/accomolate/article/details/42148501对代码进行了优化】

function pooledFeatures = cnnPool(poolDim, convolvedFeatures)%cnnPool Pools the given convolved features%% Parameters:%  poolDim - dimension of pooling region%  convolvedFeatures - convolved features to pool (as given by cnnConvolve)%                      convolvedFeatures(featureNum, imageNum, imageRow, imageCol)%% Returns:%  pooledFeatures - matrix of pooled features in the form%                   pooledFeatures(featureNum, imageNum, poolRow, poolCol)%     numImages = size(convolvedFeatures, 2);numFeatures = size(convolvedFeatures, 1);convolvedDim = size(convolvedFeatures, 3);pooledFeatures = zeros(numFeatures, numImages, floor(convolvedDim / poolDim), floor(convolvedDim / poolDim));% -------------------- YOUR CODE HERE --------------------% Instructions:%   Now pool the convolved features in regions of poolDim x poolDim,%   to obtain the %   numFeatures x numImages x (convolvedDim/poolDim) x (convolvedDim/poolDim) %   matrix pooledFeatures, such that%   pooledFeatures(featureNum, imageNum, poolRow, poolCol) is the %   value of the featureNum feature for the imageNum image pooled over the%   corresponding (poolRow, poolCol) pooling region %   (see http://ufldl/wiki/index.php/Pooling )%   %   Use mean pooling here.% -------------------- YOUR CODE HERE --------------------for imageNum = 1:numImages  for featureNum = 1:numFeatures%      convolvedFeature = squeeze(convolvedFeatures(featureNum, imageNum, :, :));      %pooledFeature = pooledFeatures(featureNum, imageNum, :, :);%       for r = 1 : size(pooledFeatures,3)%         for c = 1: size(pooledFeatures,4)%             patch = convolvedFeature(1+(r-1)*poolDim:poolDim+(r-1)*poolDim,1+(c-1)*poolDim:poolDim+(c-1)*poolDim);%             pooledFeatures(featureNum, imageNum, r, c) = mean(patch(:));%         end%       end    temp = conv2(squeeze(convolvedFeatures(featureNum, imageNum, :, :)), ones(poolDim)/(poolDim*poolDim), 'valid');    pooledFeatures(featureNum, imageNum, :, :) = temp(1:poolDim:end, 1:poolDim:end);  endendend

cnnExercise.m

%% CS294A/CS294W Convolutional Neural Networks Exercise%  Instructions%  ------------% %  This file contains code that helps you get started on the%  convolutional neural networks exercise. In this exercise, you will only%  need to modify cnnConvolve.m and cnnPool.m. You will not need to modify%  this file.%%======================================================================%% STEP 0: Initialization%  Here we initialize some parameters used for the exercise.imageDim = 64;         % image dimensionimageChannels = 3;     % number of channels (rgb, so 3)patchDim = 8;          % patch dimensionnumPatches = 50000;    % number of patchesvisibleSize = patchDim * patchDim * imageChannels;  % number of input units outputSize = visibleSize;   % number of output unitshiddenSize = 400;           % number of hidden units epsilon = 0.1;       % epsilon for ZCA whiteningpoolDim = 19;          % dimension of pooling region%%======================================================================%% STEP 1: Train a sparse autoencoder (with a linear decoder) to learn %  features from color patches. If you have completed the linear decoder%  execise, use the features that you have obtained from that exercise, %  loading them into optTheta. Recall that we have to keep around the %  parameters used in whitening (i.e., the ZCA whitening matrix and the%  meanPatch)% --------------------------- YOUR CODE HERE --------------------------% Train the sparse autoencoder and fill the following variables with % the optimal parameters:%optTheta =  zeros(2*hiddenSize*visibleSize+hiddenSize+visibleSize, 1);%ZCAWhite =  zeros(visibleSize, visibleSize);%meanPatch = zeros(visibleSize, 1);load('STL10Features.mat', 'optTheta', 'ZCAWhite', 'meanPatch');% --------------------------------------------------------------------% Display and check to see that the features look goodW = reshape(optTheta(1:visibleSize * hiddenSize), hiddenSize, visibleSize);b = optTheta(2*hiddenSize*visibleSize+1:2*hiddenSize*visibleSize+hiddenSize);displayColorNetwork( (W*ZCAWhite)');%%======================================================================%% STEP 2: Implement and test convolution and pooling%  In this step, you will implement convolution and pooling, and test them%  on a small part of the data set to ensure that you have implemented%  these two functions correctly. In the next step, you will actually%  convolve and pool the features with the STL10 images.%% STEP 2a: Implement convolution%  Implement convolution in the function cnnConvolve in cnnConvolve.m% Note that we have to preprocess the images in the exact same way % we preprocessed the patches before we can obtain the feature activations.addpath stlSubset/load stlTrainSubset.mat % loads numTrainImages, trainImages, trainLabels%% Use only the first 8 images for testingconvImages = trainImages(:, :, :, 1:8); % NOTE: Implement cnnConvolve in cnnConvolve.m first!convolvedFeatures = cnnConvolve(patchDim, hiddenSize, convImages, W, b, ZCAWhite, meanPatch);%% STEP 2b: Checking your convolution%  To ensure that you have convolved the features correctly, we have%  provided some code to compare the results of your convolution with%  activations from the sparse autoencoder% For 1000 random pointsfor i = 1:1000        featureNum = randi([1, hiddenSize]);    imageNum = randi([1, 8]);    imageRow = randi([1, imageDim - patchDim + 1]);    imageCol = randi([1, imageDim - patchDim + 1]);           patch = convImages(imageRow:imageRow + patchDim - 1, imageCol:imageCol + patchDim - 1, :, imageNum);    patch = patch(:);                patch = patch - meanPatch;    patch = ZCAWhite * patch;        features = feedForwardAutoencoder(optTheta, hiddenSize, visibleSize, patch);     if abs(features(featureNum, 1) - convolvedFeatures(featureNum, imageNum, imageRow, imageCol)) > 1e-9        fprintf('Convolved feature does not match activation from autoencoder\n');        fprintf('Feature Number    : %d\n', featureNum);        fprintf('Image Number      : %d\n', imageNum);        fprintf('Image Row         : %d\n', imageRow);        fprintf('Image Column      : %d\n', imageCol);        fprintf('Convolved feature : %0.5f\n', convolvedFeatures(featureNum, imageNum, imageRow, imageCol));        fprintf('Sparse AE feature : %0.5f\n', features(featureNum, 1));               error('Convolved feature does not match activation from autoencoder');    end enddisp('Congratulations! Your convolution code passed the test.');%% STEP 2c: Implement pooling%  Implement pooling in the function cnnPool in cnnPool.m% NOTE: Implement cnnPool in cnnPool.m first!%pooledFeatures = cnnPool(poolDim, convolvedFeatures);%% STEP 2d: Checking your pooling%  To ensure that you have implemented pooling, we will use your pooling%  function to pool over a test matrix and check the results.testMatrix = reshape(1:64, 8, 8);expectedMatrix = [mean(mean(testMatrix(1:4, 1:4))) mean(mean(testMatrix(1:4, 5:8))); ...                  mean(mean(testMatrix(5:8, 1:4))) mean(mean(testMatrix(5:8, 5:8))); ];            testMatrix = reshape(testMatrix, 1, 1, 8, 8);        pooledFeatures = squeeze(cnnPool(4, testMatrix));if ~isequal(pooledFeatures, expectedMatrix)    disp('Pooling incorrect');    disp('Expected');    disp(expectedMatrix);    disp('Got');    disp(pooledFeatures);else    disp('Congratulations! Your pooling code passed the test.');end%%======================================================================%% STEP 3: Convolve and pool with the dataset%  In this step, you will convolve each of the features you learned with%  the full large images to obtain the convolved features. You will then%  pool the convolved features to obtain the pooled features for%  classification.%%  Because the convolved features matrix is very large, we will do the%  convolution and pooling 50 features at a time to avoid running out of%  memory. Reduce this number if necessarystepSize = 50;assert(mod(hiddenSize, stepSize) == 0, 'stepSize should divide hiddenSize');load stlTrainSubset.mat % loads numTrainImages, trainImages, trainLabelsload stlTestSubset.mat  % loads numTestImages,  testImages,  testLabelspooledFeaturesTrain = zeros(hiddenSize, numTrainImages, ...    floor((imageDim - patchDim + 1) / poolDim), ...    floor((imageDim - patchDim + 1) / poolDim) );pooledFeaturesTest = zeros(hiddenSize, numTestImages, ...    floor((imageDim - patchDim + 1) / poolDim), ...    floor((imageDim - patchDim + 1) / poolDim) );tic();for convPart = 1:(hiddenSize / stepSize)        featureStart = (convPart - 1) * stepSize + 1;    featureEnd = convPart * stepSize;        fprintf('Step %d: features %d to %d\n', convPart, featureStart, featureEnd);      Wt = W(featureStart:featureEnd, :);    bt = b(featureStart:featureEnd);            fprintf('Convolving and pooling train images\n');    convolvedFeaturesThis = cnnConvolve(patchDim, stepSize, ...        trainImages, Wt, bt, ZCAWhite, meanPatch);    pooledFeaturesThis = cnnPool(poolDim, convolvedFeaturesThis);    pooledFeaturesTrain(featureStart:featureEnd, :, :, :) = pooledFeaturesThis;       toc();    clear convolvedFeaturesThis pooledFeaturesThis;        fprintf('Convolving and pooling test images\n');    convolvedFeaturesThis = cnnConvolve(patchDim, stepSize, ...        testImages, Wt, bt, ZCAWhite, meanPatch);    pooledFeaturesThis = cnnPool(poolDim, convolvedFeaturesThis);    pooledFeaturesTest(featureStart:featureEnd, :, :, :) = pooledFeaturesThis;       toc();    clear convolvedFeaturesThis pooledFeaturesThis;end% You might want to save the pooled features since convolution and pooling takes a long timesave('cnnPooledFeatures.mat', 'pooledFeaturesTrain', 'pooledFeaturesTest');toc();%%======================================================================%% STEP 4: Use pooled features for classification%  Now, you will use your pooled features to train a softmax classifier,%  using softmaxTrain from the softmax exercise.%  Training the softmax classifer for 1000 iterations should take less than%  10 minutes.% Add the path to your softmax solution, if necessary% addpath /path/to/solution/% Setup parameters for softmaxsoftmaxLambda = 1e-4;numClasses = 4;% Reshape the pooledFeatures to form an input vector for softmaxsoftmaxX = permute(pooledFeaturesTrain, [1 3 4 2]);%通过交换维度以后，softmaxX(:,:,:,k)就对应着第k幅图的pooling特征softmaxX = reshape(softmaxX, numel(pooledFeaturesTrain) / numTrainImages,...    numTrainImages); %numel(pooledFeaturesTrain)/numTrainImages的结果是softmaxX前3个维度的乘积，也就是一幅图在所有特征上形成的针对该图的特征的大小softmaxY = trainLabels;options = struct;options.maxIter = 200;softmaxModel = softmaxTrain(numel(pooledFeaturesTrain) / numTrainImages,...    numClasses, softmaxLambda, softmaxX, softmaxY, options);%%======================================================================%% STEP 5: Test classifer%  Now you will test your trained classifer against the test imagessoftmaxX = permute(pooledFeaturesTest, [1 3 4 2]);softmaxX = reshape(softmaxX, numel(pooledFeaturesTest) / numTestImages, numTestImages);softmaxY = testLabels;[pred] = softmaxPredict(softmaxModel, softmaxX);acc = (pred(:) == softmaxY(:));acc = sum(acc) / size(acc, 1);fprintf('Accuracy: %2.3f%%\n', acc * 100);% You should expect to get an accuracy of around 80% on the test images.

结果：Accuracy: 80.094%

用时：3148.905 s

参考资料：
1.http://blog.csdn.net/accomolate/article/details/42148501

2.http://deeplearning.stanford.edu/wiki/index.php/Exercise:Convolution_and_Pooling