大数据机器学习


DZone, Inc. | www.dzone.com Get More Refcardz! Visit refcardz.com #158 Machine Learning By Ricky Ho INTRODUCTION Predictive Analytics is about predicting future outcome based on analyzing data collected previously. It includes two phases: 1. Training phase: Learn a model from training data 2. Predicting phase: Use the model to predict the unknown or future outcome PREDICTIVE MODELS We can choose many models, each based on a set of different assumptions regarding the underlying distribution of data. Therefore, we are interested in two general types of problems in this discussion: 1. Classification—about predicting a category (a value that is discrete, finite with no ordering implied), and 2. Regression—about predicting a numeric quantity (a value that’s continuous and infinite with ordering). For classification problems, we use the “iris” data set and predict its “species” from its “width” and “length” measures of sepals and petals. Here is how we set up our training and testing data: > summary(iris) Sepal.Length Sepal.Width Petal.Length Petal.Width Min. :4.300000 Min. :2.000000 Min. :1.000 Min. :0.100000 1st Qu.:5.100000 1st Qu.:2.800000 1st Qu.:1.600 1st Qu.:0.300000 Median :5.800000 Median :3.000000 Median :4.350 Median :1.300000 Mean :5.843333 Mean :3.057333 Mean :3.758 Mean :1.199333 3rd Qu.:6.400000 3rd Qu.:3.300000 3rd Qu.:5.100 3rd Qu.:1.800000 Max. :7.900000 Max. :4.400000 Max. :6.900 Max. :2.500000 Species setosa :50 versicolor:50 virginica :50 > head(iris) Sepal.Length Sepal.Width Petal.Length Petal.Width Species 1 5.1 3.5 1.4 0.2 setosa 2 4.9 3.0 1.4 0.2 setosa 3 4.7 3.2 1.3 0.2 setosa 4 4.6 3.1 1.5 0.2 setosa 5 5.0 3.6 1.4 0.2 setosa 6 5.4 3.9 1.7 0.4 setosa > > # Prepare training and testing data > testidx <- which(1:length(iris[,1])%%5 == 0) > iristrain <- iris[-testidx,] > iristest <- iris[testidx,] To illustrate a regression problem (where the output we predict is a numeric quantity), we’ll use the “Prestige” data set imported from the “car” package to create our training and testing data. > library(car) > summary(Prestige) education income women Min. : 6.38000 Min. : 611.000 Min. : 0.00000 1st Qu.: 8.44500 1st Qu.: 4106.000 1st Qu.: 3.59250 Median :10.54000 Median : 5930.500 Median :13.60000 Mean :10.73804 Mean : 6797.902 Mean :28.97902 3rd Qu.:12.64750 3rd Qu.: 8187.250 3rd Qu.:52.20250 Max. :15.97000 Max. :25879.000 Max. :97.51000 prestige census type Min. :14.80000 Min. :1113.000 bc :44 1st Qu.:35.22500 1st Qu.:3120.500 prof:31 Median :43.60000 Median :5135.000 wc :23 Mean :46.83333 Mean :5401.775 NA’s: 4 3rd Qu.:59.27500 3rd Qu.:8312.500 Max. :87.20000 Max. :9517.000 > head(Prestige) education income women prestige census type gov.administrators 13.11 12351 11.16 68.8 1113 prof general.managers 12.26 25879 4.02 69.1 1130 prof accountants 12.77 9271 15.70 63.4 1171 prof purchasing.officers 11.42 8865 9.11 56.8 1175 prof chemists 14.62 8403 11.68 73.5 2111 prof physicists 15.64 11030 5.13 77.6 2113 prof > testidx <- which(1:nrow(Prestige)%%4==0) > prestige_train <- Prestige[-testidx,] > prestige_test <- Prestige[testidx,] LINEAR REGRESSION Linear regression has the longest, most well-understood history in statistics, and is the most popular machine learning model. It is based on the assumption that a linear relationship exists between the input and output variables, as follows: y = Ө0 + Ө1x1 + Ө 2x2 + … …where y is the output numeric value, and xi is the input numeric value. CONTENTS INCLUDE n Predictive Models n Linear Regression n Logisitic Regression n Regression with Regularization n Neural Network n And more... Big Data Machine Learning: Patterns for Predictive Analytics 2 Machine Learning DZone, Inc. | www.dzone.com The learning algorithm will learn the set of parameters such that the sum of square error (yactual - yestimate)2 is minimized. Here is the sample code that uses the R language to predict the output “prestige” from a set of input variables: > model <- lm(prestige~., data=prestige_train) > # Use the model to predict the output of test data > prediction <- predict(model, newdata=prestige_test) > # Check for the correlation with actual result > cor(prediction, prestige_test$prestige) [1] 0.9376719009 > summary(model) Call: lm(formula = prestige ~ ., data = prestige_train) Residuals: Min 1Q Median 3Q Max -13.9078951 -5.0335742 0.3158978 5.3830764 17.8851752 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) -20.7073113585 11.4213272697 -1.81304 0.0743733 . education 4.2010288017 0.8290800388 5.06710 0.0000034862 *** income 0.0011503739 0.0003510866 3.27661 0.0016769 ** women 0.0363017610 0.0400627159 0.90612 0.3681668 census 0.0018644881 0.0009913473 1.88076 0.0644172 . typeprof 11.3129416488 7.3932217287 1.53018 0.1307520 typewc 1.9873305448 4.9579992452 0.40083 0.6898376 --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 7.41604 on 66 degrees of freedom (4 observations deleted due to missingness) Multiple R-squared: 0.820444, Adjusted R-squared: 0.8041207 F-statistic: 50.26222 on 6 and 66 DF, p-value: < 0.00000000000000022204 The coefficient column gives an estimation of ƟӨi, and an associated p-value gives the confidence of each estimated ƟӨi. For example, features not marked with at least one * can be safely ignored. In the above model, education and income has a high influence to the prestige. The goal of minimizing the square error makes linear regression very sensitive to outliers that greatly deviate in the output. It is a common practice to identify those outliers, remove them, and then rerun the training. LOGISTIC REGRESSION In a classification problem, the output is binary rather than numeric. We can imagine doing a linear regression and then compressing the numeric output into a 0..1 range using the logit function 1/(1+e-t), shown here: y = 1/(1 + e -(Ө 0 + Ө1 x 1 +ƟӨ2 x 2 + …)) …where y is the 0 .. 1 value, and xi is the input numeric value. The learning algorithm will learn the set of parameters such that the cost (yactual * log yestimate + (1 - yactual) * log(1 - yestimate)) is minimized. Here is the sample code that uses the R language to perform a binary classification using iris data. > newcol = data.frame(isSetosa=(iristrain$Species == ‘setosa’)) > traindata <- cbind(iristrain, newcol) > head(traindata) Sepal.Length Sepal.Width Petal.Length Petal.Width Species isSetosa 1 5.1 3.5 1.4 0.2 setosa TRUE 2 4.9 3.0 1.4 0.2 setosa TRUE 3 4.7 3.2 1.3 0.2 setosa TRUE 4 4.6 3.1 1.5 0.2 setosa TRUE 6 5.4 3.9 1.7 0.4 setosa TRUE 7 4.6 3.4 1.4 0.3 setosa TRUE > formula <- isSetosa ~ Sepal.Length + Sepal.Width + Petal.Length + Petal.Width > logisticModel <- glm(formula, data=traindata, family=”binomial”) Warning messages: 1: glm.fit: algorithm did not converge 2: glm.fit: fitted probabilities numerically 0 or 1 occurred > # Predict the probability for test data > prob <- predict(logisticModel, newdata=iristest, type=’response’) > round(prob, 3) 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 105 110 115 120 125 130 135 140 145 150 0 0 0 0 0 0 0 0 0 0 REGRESSION WITH REGULARIZATION To avoid an over-fitting problem (the trained model fits too well with the training data and is not generalized enough), the regularization technique is used to shrink the magnitude of ƟӨi. This is done by adding a penalty (a function of the sum of ƟӨi) into the cost function. In L2 regularization (also known as Ridge regression), Өi 2 will be added to the cost function. In L1 regularization (also known as Lasso regression), Σ ||Өi|| will be added to the cost function. Both L1, L2 will shrink the magnitude of Өi. For variables that are inter-dependent, L2 tends to spread the shrinkage such that all interdependent variables are equally influential. On the other hand, L1 tends to keep one variable and shrink all the other dependent variables to values very close to zero. In other words, L1 shrinks the variables in an uneven manner so that it can also be used to select input variables. Combining L1 and L2, the general form of the cost function becomes the following: Cost == Non-regularization-cost + λ (α.Σ ||Ɵi|| + (1- α).Σ Ɵi 2) Notice the 2 tunable parameters, lambda, and alpha. Lambda controls the degree of regularization (0 means no regularization and infinity means ignoring all input variables because all coefficients of them will be zero). Alpha controls the degree of mix between L1 and L2 (0 means pure L2 and 1 means pure L1). Glmnet is a popular regularization package. The alpha parameter needs to be supplied based on the application’s need, i.e., its need for selecting a reduced set of variables. Alpha=1 is preferred. The library provides a cross-validation test to automatically choose the better lambda value. Let’s repeat the above linear regression example and use regularization this time. We pick alpha = 0.7 to favor L1 regularization. > library(glmnet) > cv.fit <- cv.glmnet(as.matrix(prestige_train[,c(-4, -6)]), as.vector(prestige_ train[,4]), nlambda=100, alpha=0.7, family=”gaussian”) > plot(cv.fit) > coef(cv.fit) 5 x 1 sparse Matrix of class “dgCMatrix” 1 (Intercept) 6.3876684930151 education 3.2111461944976 income 0.0009473793366 women 0.0000000000000 census 0.0000000000000 > prediction <- predict(cv.fit, newx=as.matrix(prestige_test[,c(-4, -6)])) > cor(prediction, as.vector(prestige_test[,4])) [,1] 1 0.9291181193 This is the cross-validation plot. It shows the best lambda with minimal-root,mean-square error. 3 Machine Learning DZone, Inc. | www.dzone.com NEURAL NETWORK A Neural Network emulates the structure of a human brain as a network of neurons that are interconnected to each other. Each neuron is technically equivalent to a logistic regression unit. In this setting, neurons are organized in multiple layers where every neuron at layer i connects to every neuron at layer i+1 and nothing else. The tuning parameters in a neural network include the number of hidden layers (commonly set to 1), the number of neurons in each layer (which should be same for all hidden layers and usually at 1 to 3 times the input variables), and the learning rate. On the other hand, the number of neurons at the output layer depends on how many binary outputs need to be learned. In a classification problem, this is typically the number of possible values at the output category. The learning happens via an iterative feedback mechanism where the error of training data output is used to adjust the corresponding weights of input. This adjustment propagates to previous layers and the learning algorithm is known as “back- propagation.” Here is an example: > library(neuralnet) > nnet_iristrain <-iristrain > #Binarize the categorical output > nnet_iristrain <- cbind(nnet_iristrain, iristrain$Species == ‘setosa’) > nnet_iristrain <- cbind(nnet_iristrain, iristrain$Species == ‘versicolor’) > nnet_iristrain <- cbind(nnet_iristrain, iristrain$Species == ‘virginica’) > names(nnet_iristrain)[6] <- ‘setosa’ > names(nnet_iristrain)[7] <- ‘versicolor’ > names(nnet_iristrain)[8] <- ‘virginica’ > nn <- neuralnet(setosa+versicolor+virginica ~ Sepal.Length + Sepal.Width + Petal.Length + Petal.Width, data=nnet_iristrain, hidden=c(3)) > plot(nn) > mypredict <- compute(nn, iristest[-5])$net.result > # Consolidate multiple binary output back to categorical output > maxidx <- function(arr) { + return(which(arr == max(arr))) + } > idx <- apply(mypredict, c(1), maxidx) > prediction <- c(‘setosa’, ‘versicolor’, ‘virginica’)[idx] > table(prediction, iristest$Species) prediction setosa versicolor virginica setosa 10 0 0 versicolor 0 10 3 virginica 0 0 7 Neural networks are very good at learning non-linear functions. They can even learn multiple outputs simultaneously, though the training time is relatively long, which makes the network susceptible to local minimum traps. This can be mitigated by doing multiple rounds and picking the best-learned model. SUPPORT VECTOR MACHINE A Support Vector Machine provides a binary classification mechanism based on finding a hyperplane between a set of samples with +ve and -ve outputs. It assumes the data is linearly separable. The problem can be structured as a quadratic programming optimization problem that maximizes the margin subjected to a set of linear constraints (i.e., data output on one side of the line must be +ve while the other side must be -ve). This can be solved with the quadratic programming technique. 4 Machine Learning DZone, Inc. | www.dzone.com If the data is not linearly separable due to noise (the majority is still linearly separable), then an error term will be added to penalize the optimization. If the data distribution is fundamentally non-linear, the trick is to transform the data to a higher dimension so the data will be linearly separable.The optimization term turns out to be a dot product of the transformed points in the high-dimension space, which is found to be equivalent to performing a kernel function in the original (before transformation) space. The kernel function provides a cheap way to equivalently transform the original point to a high dimension (since we don’t actually transform it) and perform the quadratic optimization in that high-dimension space. There are a couple of tuning parameters (e.g., penalty and cost), so transformation is usually conducted in 2 steps—finding the optimal parameter and then training the SVM model using that parameter. Here are some example codes in R: > library(e1071) > tune <- tune.svm(Species~., data=iristrain, gamma=10^(-6:-1), cost=10^(1:4)) > summary(tune) Parameter tuning of ‘svm’: - sampling method: 10-fold cross validation - best parameters: gamma cost 0.001 10000 - best performance: 0.03333333 > model <- svm(Species~., data=iristrain, method=”C-classification”, kernel=”radial”, probability=T, gamma=0.001, cost=10000) > prediction <- predict(model, iristest, probability=T) > table(iristest$Species, prediction) prediction setosa versicolor virginica setosa 10 0 0 versicolor 0 10 0 virginica 0 3 7 > SVM with a Kernel function is a highly effective model and works well across a wide range of problem sets. Although it is a binary classifier, it can be easily extended to a multi-class classification by training a group of binary classifiers and using “one vs all” or “one vs one” as predictors. SVM predicts the output based on the distance to the dividing hyperplane. This doesn’t directly estimate the probability of the prediction. We therefore use the calibration technique to find a logistic regression model between the distance of the hyperplane and the binary output. Using that regression model, we then get our estimation. BAYESIAN NETWORK AND NAÏVE BAYES From a probabilistic viewpoint, the predictive problem can be viewed as a conditional probability estimation; trying to find Y where P(Y | X) is maximized. From the Bayesian rule, P(Y | X) == P(X | Y) * P(Y) / P(X) This is equivalent to finding Y where P(X | Y) * P(Y) is maximized. Let’s say the input X contains 3 categorical features— X1, X2, X3. In the general case, we assume each variable can potentially influence any other variable. Therefore the joint distribution becomes: P(X | Y) = P(X1 | Y) * P(X2 | X1, Y) * P(X3 | X1, X2, Y) Notice how in the last term of the above equation, the number of entries is exponentially proportional to the number of input variables. Since P(X | Y) == P(X1 | Y) * P(X2 | Y) * P(X3 | Y), we need to find the Y that maximizes P(X1 | Y) * P(X2 | Y) * P(X3 | Y) * P(Y) Each term on the right hand side can be learned by counting the training data. Therefore we can estimate P(Y | X) and pick Y to maximize its value. But it is possible that some patterns never show up in training data, e.g., P(X1=a | Y=y) is 0. To deal with this situation, we pretend to have seen the data of each possible value one more time than we actually have. P(X1=a | Y=y) == (count(a, y) + 1) / (count(y) + m) …where m is the number of possible values in X1. When the input features are numeric, say a = 2.75, we can assume X1 is the normal distribution. Find out the mean and standard deviation of X1 and then estimate P(X1=a) using the normal distribution function. Here is how we use Naïve Bayes in R: > library(e1071) > # Can handle both categorical and numeric input variables, but output must be categorical > model <- naiveBayes(Species~., data=iristrain) > prediction <- predict(model, iristest[,-5]) > table(prediction, iristest[,5]) prediction setosa versicolor virginica setosa 10 0 0 versicolor 0 10 2 virginica 0 0 8 Notice the independence assumption is not true in most cases.Nevertheless, the system still performs incredibly well. Onestrength of Naïve Bayes is that it is highly scalable and can learn incrementally—all we have to do is count the observed variables and update the probability distribution. K-NEAREST NEIGHBORS A contrast to model-based learning is K-Nearest neighbor. This is also called instance-based learning because it doesn’t even learn a single model. The training process involves memorizing all the training data. To predict a new data point, we found the closest K (a tunable parameter) neighbors from the training set and let them vote for the final prediction. 5 Machine Learning DZone, Inc. | www.dzone.com To determine the “nearest neighbors,” a distance function needs to be defined (e.g., a Euclidean distance function is a common one for numeric input variables). The voting can also be weighted among the K-neighbors based on their distance from the new data point. Here is the R code using K-nearest neighbor for classification. > library(class) > train_input <- as.matrix(iristrain[,-5]) > train_output <- as.vector(iristrain[,5]) > test_input <- as.matrix(iristest[,-5]) > prediction <- knn(train_input, test_input, train_output, k=5) > table(prediction, iristest$Species) prediction setosa versicolor virginica setosa 10 0 0 versicolor 0 10 1 virginica 0 0 9 > The strength of K-nearest neighbor is its simplicity. No model needs to be trained. Incremental learning is automatic when more data arrives (and old data can be deleted as well). The weakness of KNN, however, is that it doesn’t handle high numbers of dimensions well. DECISION TREE Based on a tree of decision nodes, the learning approach is to recursively divide the training data into buckets of homogeneous members through the most discriminative dividing criteria possible. The measurement of “homogeneity” is based on the output label; when it is a numeric value, the measurement will be the variance of the bucket; when it is a category, the measurement will be the entropy, or “gini index,” of the bucket. During the training, various dividing criteria based on the input will be tried (and used in a greedy manner); when the input is a category (Mon, Tue, Wed, etc.), it will first be turned into binary (isMon, isTue, isWed, etc.,) and then it will use true/false as a decision boundary to evaluate homogeneity; when the input is a numeric or ordinal value, the lessThan/greaterThan at each training-data input value will serve as the decision boundary. The training process stops when there is no significant gain in homogeneity after further splitting the Tree. The members of the bucket represented at leaf node will vote for the prediction; the majority wins when the output is a category. The member’s average is taken when the output is a numeric. Here is an example in R: > library(rpart) > #Train the decision tree > treemodel <- rpart(Species~., data=iristrain) > plot(treemodel) > text(treemodel, use.n=T) > #Predict using the decision tree > prediction <- predict(treemodel, newdata=iristest, type=’class’) > #Use contingency table to see how accurate it is > table(prediction, iristest$Species) prediction setosa versicolor virginica setosa 10 0 0 versicolor 0 10 3 virginica 0 0 7 > names(nnet_iristrain)[8] <- ‘virginica’ Here is the Tree model that has been learned: The good part of the Tree is that it can take different data types of input and output variables that can be categorical, binary and numeric values. It can handle missing attributes and outliers well. Decision Tree is also good in explaining reasoning for its prediction and therefore gives good insight about the underlying data. The limitation of Decision Tree is that each decision boundary at each split point is a concrete binary decision. Also, the decision criteria considers only one input attribute at a time, not a combination of multiple input variables. Another weakness of Decision Tree is that once learned it cannot be updated incrementally. When new training data arrives, you have to throw away the old tree and retrain all data from scratch. In practice, standalone decision trees are rarely used because their accuracy ispredictive and relatively low . Tree ensembles (described below) are the common way to use decision trees. TREE ENSEMBLES Instead of picking a single model, Ensemble Method combines multiple models in a certain way to fit the training data. Here are the two primary ways: “bagging” and “boosting.” In “bagging”, we take a subset of training data (pick n random sample out of N training data, with replacement) to train up each model. After multiple models are trained, we use a voting scheme to predict future data. Random Forest is one of the most popular bagging models; in addition to selecting n training data out of N at each decision node of the tree, it randomly selects m input features from the total M input features (m ~ M^0.5). Then it learns a decision tree from that. Finally, each tree in the forest votes for the result. Here is the R code to use Random Forest: > library(randomForest) #Train 100 trees, random selected attributes > model <- randomForest(Species~., data=iristrain, nTree=500) #Predict using the forest > prediction <- predict(model, newdata=iristest, type=’class’) > table(prediction, iristest$Species) > importance(model) MeanDecreaseGini Sepal.Length 7.807602 Sepal.Width 1.677239 Petal.Length 31.145822 Petal.Width 38.617223 “Boosting” is another approach in Ensemble Method. Instead of sampling the input features, it samples the training data records. It puts more emphasis, though, on the training data that is wrongly predicted in previous iterations. Initially, each training data is equally weighted. At each iteration, the data that is wrongly classified will have its weight increased. Gradient Boosting Method is one of the most popular boosting methods. It is based on incrementally adding a function that fits the residuals. Set i = 0 at the beginning, and repeat until convergence. • Learn a function Fi(X) to predict Y. Basically, find F that minimizes the expected(L(F(X) – Y)), where L is the lost function of the residual • Learning another function gi(X) to predict the gradient of the above function 6 Machine Learning RECOMMENDED BOOK • Update Fi+1 = Fi + a.gi(X), where a is the learning rate Below is Gradient-Boosted Tree using the decision tree as the learning model F. Here is the sample code in R: > library(gbm) > iris2 <- iris > newcol = data.frame(isVersicolor=(iris2$Species==’versicolor’)) > iris2 <- cbind(iris2, newcol) > iris2[45:55,] Sepal.Length Sepal.Width Petal.Length Petal.Width Species isVersicolor 45 5.1 3.8 1.9 0.4 setosa FALSE 46 4.8 3.0 1.4 0.3 setosa FALSE 47 5.1 3.8 1.6 0.2 setosa FALSE 48 4.6 3.2 1.4 0.2 setosa FALSE 49 5.3 3.7 1.5 0.2 setosa FALSE 50 5.0 3.3 1.4 0.2 setosa FALSE 51 7.0 3.2 4.7 1.4 versicolor TRUE 52 6.4 3.2 4.5 1.5 versicolor TRUE 53 6.9 3.1 4.9 1.5 versicolor TRUE 54 5.5 2.3 4.0 1.3 versicolor TRUE 55 6.5 2.8 4.6 1.5 versicolor TRUE > formula <- isVersicolor ~ Sepal.Length + Sepal.Width + Petal.Length + Petal. Width > model <- gbm(formula, data=iris2, n.trees=1000, interaction.depth=2, distribution=”bernoulli”) Iter TrainDeviance ValidDeviance StepSize Improve 1 1.2714 -1.#IND 0.0010 0.0008 2 1.2705 -1.#IND 0.0010 0.0004 3 1.2688 -1.#IND 0.0010 0.0007 4 1.2671 -1.#IND 0.0010 0.0008 5 1.2655 -1.#IND 0.0010 0.0008 6 1.2639 -1.#IND 0.0010 0.0007 7 1.2621 -1.#IND 0.0010 0.0008 8 1.2614 -1.#IND 0.0010 0.0003 9 1.2597 -1.#IND 0.0010 0.0008 10 1.2580 -1.#IND 0.0010 0.0008 100 1.1295 -1.#IND 0.0010 0.0008 200 1.0090 -1.#IND 0.0010 0.0005 300 0.9089 -1.#IND 0.0010 0.0005 400 0.8241 -1.#IND 0.0010 0.0004 500 0.7513 -1.#IND 0.0010 0.0004 600 0.6853 -1.#IND 0.0010 0.0003 700 0.6266 -1.#IND 0.0010 0.0003 800 0.5755 -1.#IND 0.0010 0.0002 900 0.5302 -1.#IND 0.0010 0.0002 1000 0.4901 -1.#IND 0.0010 0.0002 > prediction <- predict.gbm(model, iris2[45:55,], type=”response”, n.trees=1000) > round(prediction, 3) [1] 0.127 0.131 0.127 0.127 0.127 0.127 0.687 0.688 0.572 0.734 0.722 > summary(model) var rel.inf 1 Petal.Length 61.4203761582 2 Petal.Width 34.7557511871 3 Sepal.Width 3.5407662531 4 Sepal.Length 0.2831064016 The GBM R package also gave the relative importance of the input features, as shown in the bar graph. By Paul M. Duvall ABOUT CON TINUOUS INTEGRA TION Get Mor e Refcar dz! V isit r efcar dz.com #84 Continuous Integration:Patterns and Anti-PatternsCONTENTS INCLUDE: ■ About Continuous Integration ■ Build Softwar e at Every Change ■ Patterns and Anti-patter ns ■ Version Contr ol ■ Build Management ■ Build Practices and mor e... Continuous Integration (CI) is the pr ocess of building softwar e with every change committed to a pr oject’s version contr ol repository . CI can be explained via patterns (i.e. , a solution to a pr oblem in a particular context) and anti-patter ns (i.e., inef fective appr oaches sometimes used to “fi x” the particular problem) associated with the pr ocess. Anti-patterns ar e solutions that appear to be benefi cial, but, in the end, they tend to prod uce adverse ef fects. They ar e not necessarily bad practices, but can produce unintended r esults when compar ed to implementing the pattern. Continuous Integration While the conventional use of the term Continuous Integration efers to the “build and test” cycle, t his Refcar d expands on the notion of CI to inclu de concepts such as Aldon® Change . Collaborat e. Comply. Pattern Description Private W orkspace Develop softwar e in a Private W orkspace to isolat e changes Repository Commit all fi les to a version-co ntrol repository Mainline Develop on a main line to minimize me rging and to manag e active code lines Codeline Policy Developing softw are within a system t hat utilizes multiple codelines Task-Level Comm it Organize sour ce code changes by task-oriented uni ts of work and submit chang es as a T ask Level Commit Label Build Label the build wit h unique name Automated Build Automate all activiti es to build softwar e from sour ce without manual confi guration Minimal Dependen cies Reduce pr e-installed tool de pendencies to the b are minimum Binary Integrity For each tagged deployment, use th e same deployment package (e.g. W AR or EAR) in each target envir onment Dependency Ma nagement Centralize all depen dent libraries Template V erifi er Create a single templa te fi le that all tar get envir onment properties ar e based on Staged Builds Run remote builds into di fferent target envir onments Private Build Perform a Private Build befor e committing chang es to the Repository Integration Build Perform an Integra tion Build periodical ly, continually , etc. Send automated fe edback fr om CI server to d evelopment team ors as soon as they occur Generate develope r documentation with builds based on brought to you by ... By Andy Harris HTML BASICS e.com Get Mor e Refcar dz! V isit r efcar dz.com #64 Core HTMLHTML and XHTML ar e the foundation of all web development. HTML is used as the graphical user interface in client-side programs written in JavaScript. Server -side languages like PHP and Java also r eceive data fr om web pages and use HTML as the output mechanism. The emer ging Ajax technologies likewise use HTML and XHTML as their visual engine. HTML was once a very loosely-defi ned language with very little standar dization, but as it has become mor e important, the need for standar ds has become mor e appar ent. Regar dless of whether you choose to write HTML or XHTML, understanding the curr ent standar ds will help you pr ovide a solid foundation that will simplify all your other web coding. Fortunately HTML and XHTML ar e actually simpler than they used to be, because much of the functionality has moved to CSS. common element sEvery page (HTML or XHTML shar es certain elements in common.) All ar e essentially plain text extension. HTML fi les should not be crprocessor CONTENTS INCLUDE: ■ HTML Basics ■ HTML vs XHTML ■ Validation ■ Useful Open Sour ce Tools ■ Page Structur e Elements■ Key Structural Elements and mor e... The sr c attribute describes wher e the image fi le can be found, and the alt attribute describes alternate text that is displayed if the image is unavailable. Nested tags Tags can be (and fr equently ar e) nested inside each other . Tags cannot overlap, so is not legal, but is fi ne. HTML VS XHTML HTML has been ar ound for some time. While it has done its job admirably , that job has expanded far mor e than anybody expected. Early HTML had very limited layout support. Browser manufactur ers added many competing standarweb developers came up with clever workar result is a lack of standar The latest web standar Browse our collection of over Free Cheat Sheets Upcoming Refcardz By Daniel Rubio ABOUT CLOUD COMPUTING Cloud Computing www .d zon e.com Get Mor e Refcar dz! V isit r efcar dz.com #82 Getting Started with Cloud Computing CONTENTS INCLUDE: ■ About Cloud Computing ■ Usage Scenarios ■ Underlying Concepts ■ Cost ■ Data Tier Technologies ■ Platform Management and more... Web applications have always been deployed on servers connected to what is now deemed the ‘cloud’. However, the demands and technology used on such servers has changed substantially in recent years, especially with the entrance of service providers like Amazon, Google and Microsoft. These companies have long deployed web applications that adapt and scale to large user bases, making them knowledgeable in many aspects related to cloud computing. This Refcard will introduce to you to cloud computing, with an emphasis on these providers, so you can better understand what it is a cloud computing platform can offer your web applications. USAGE SCENARIOS Pay only what you consume Web application deployment until a few years ago was similar to most phone services: plans with alloted resources, with an incurred cost whether such resources were consumed or not. Cloud computing as it’s known today has changed this. The various resources consumed by web applications (e.g. bandwidth, memory, CPU) are tallied on a per-unit basis (starting from zero) by all major cloud computing platforms. also minimizes the need to make design changes to support one time events. Automated growth & scalable technologies Having the capability to support one time events, cloud computing platforms also facilitate the gradual growth curves faced by web applications. Large scale growth scenarios involving specialized equipment (e.g. load balancers and clusters) are all but abstracted away by relying on a cloud computing platform’s technology. In addition, several cloud computing platforms support data tier technologies that exceed the precedent set by Relational Database Systems (RDBMS): Map Reduce, web service APIs, etc. Some platforms support large scale RDBMS deployments. CLOUD COMPUTING PLATFORMS AND UNDERLYING CONCEPTS Amazon EC2: Industry standard software and virtualization Amazon’s cloud computing platform is heavily based on industry standard software and virtualization technology. Virtualization allows a physical piece of hardware to be utilized by multiple operating systems. This allows resources (e.g. bandwidth, memory, CPU) to be allocated exclusively to individual operating system instances. As a user of Amazon’s EC2 cloud computing platform, you are assigned an operating system in the same way as on all hosting 150 Scala Collections VisualVM Opa Data Warehousing ABOUT THE AUTHOR DZone, Inc. 150 Preston Executive Dr. Suite 200 Cary, NC 27513 888.678.0399 919.678.0300 Refcardz Feedback Welcome refcardz@dzone.com Sponsorship Opportunities sales@dzone.com Copyright © 2012 DZone, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Version 1.0 $7.95 DZone communities deliver over 6 million pages each month to more than 3.3 million software developers, architects and decision makers. DZone offers something for everyone, including news, tutorials, cheat sheets, blogs, feature articles, source code and more. “DZone is a developer’s dream,” says PC Magazine. Ricky has spent the last 20 years developing and designing large scale software systems including software gateways, fraud detection, cloud computing, web analytics, and online advertising. He has played different roles from architect to developer and consultant in helping companies to apply statistics, machine learning, and optimization techniques to extract useful insight from their raw data, and also predict business trends. Ricky has 9 patents in the areas of distributed systems, cloud computing and real-time analytics. He is very passionate about algorithms and problem solving. He is an active blogger and maintains a technical blog to share his ideas at http://horicky.blogspot.com Introduction to Data Mining covers all aspects of data mining, taking both theoretical and practical approaches to introduce a complex field to those learning data mining for the first time. Copious figures and examples bridge the gap from abstract to hands-on. The book requires only basic background in statistics, and requires no background in databases. Includes detailed treatment of predictive modeling, association analysis, clustering, anomaly detection, visualization, and more. http://www-users.cs.umn. edu/~kumar/dmbook/index.php
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