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**Machine Learning on Spark**

Shivaram Venkataraman UC Berkeley

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Machine learning Computer Science Statistics

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**Machine learning Spam ﬁlters Click prediction Recommendations**

Search ranking

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**Machine learning techniques Classification Clustering Regression**

Active learning Collaborative filtering

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**Implementing Machine Learning**

Machine learning algorithms are Complex, multi-stage Iterative MapReduce/Hadoop unsuitable Need efficient primitives for data sharing

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**Machine Learning using Spark**

Spark RDDs efficient data sharing In-memory caching accelerates performance Up to 20x faster than Hadoop Easy to use high-level programming interface Express complex algorithms ~100 lines.

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**Machine learning techniques Classification Clustering Regression**

Active learning Collaborative filtering

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**K-Means Clustering using Spark**

Focus: Implementation and Performance

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**Grouping data according to similarity**

Clustering E.g. archaeological dig Clustering applications – applications – image recognition Distance North Grouping data according to similarity Distance East

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**Grouping data according to similarity**

Clustering E.g. archaeological dig Clustering applications – applications – image recognition Distance North Grouping data according to similarity Distance East

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**K-Means Algorithm E.g. archaeological dig Distance North Distance East**

Benefits Popular Fast Conceptually straightforward E.g. archaeological dig Clustering applications – applications – image recognition Distance North Distance East

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**K-Means: preliminaries**

Data: Collection of values Clustering applications – applications – image recognition data = lines.map(line=> parseVector(line)) Feature 2 Feature 1

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**K-Means: preliminaries**

Dissimilarity: Squared Euclidean distance Clustering applications – applications – image recognition Feature 2 dist = p.squaredDist(q) Feature 1

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**K-Means: preliminaries**

K = Number of clusters Clustering applications – applications – image recognition Feature 2 Data assignments to clusters S1, S2,. . ., SK Feature 1

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**K-Means: preliminaries**

K = Number of clusters Clustering applications – applications – image recognition Feature 2 Data assignments to clusters S1, S2,. . ., SK Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each data point to the cluster with the closest center. Assign each cluster center to be the mean of its cluster’s data points. Clustering applications – applications – image recognition Feature 2 Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each data point to the cluster with the closest center. Assign each cluster center to be the mean of its cluster’s data points. Clustering applications – applications – image recognition Feature 2 Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each data point to the cluster with the closest center. Assign each cluster center to be the mean of its cluster’s data points. centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each data point to the cluster with the closest center. Assign each cluster center to be the mean of its cluster’s data points. centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each data point to the cluster with the closest center. Assign each cluster center to be the mean of its cluster’s data points. centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each cluster center to be the mean of its cluster’s data points. centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 closest = data.map(p => (closestPoint(p,centers),p)) Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each cluster center to be the mean of its cluster’s data points. centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 closest = data.map(p => (closestPoint(p,centers),p)) Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: Assign each cluster center to be the mean of its cluster’s data points. centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 closest = data.map(p => (closestPoint(p,centers),p)) Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 closest = data.map(p => (closestPoint(p,centers),p)) pointsGroup = closest.groupByKey() Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 closest = data.map(p => (closestPoint(p,centers),p)) pointsGroup = closest.groupByKey() newCenters = pointsGroup.mapValues( ps => average(ps)) Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 closest = data.map(p => (closestPoint(p,centers),p)) pointsGroup = closest.groupByKey() newCenters = pointsGroup.mapValues( ps => average(ps)) Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 closest = data.map(p => (closestPoint(p,centers),p)) pointsGroup = closest.groupByKey() newCenters = pointsGroup.mapValues( ps => average(ps)) Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 while (dist(centers, newCenters) > ɛ) closest = data.map(p => (closestPoint(p,centers),p)) pointsGroup = closest.groupByKey() newCenters =pointsGroup.mapValues( ps => average(ps)) Feature 1

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**K-Means Algorithm • Initialize K cluster centers**

• Repeat until convergence: centers = data.takeSample( false, K, seed) Clustering applications – applications – image recognition Feature 2 while (dist(centers, newCenters) > ɛ) closest = data.map(p => (closestPoint(p,centers),p)) pointsGroup = closest.groupByKey() newCenters =pointsGroup.mapValues( ps => average(ps)) Feature 1

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**K-Means Source Feature 2 Feature 1 centers = data.takeSample(**

false, K, seed) while (d > ɛ) { Clustering applications – applications – image recognition closest = data.map(p => (closestPoint(p,centers),p)) Feature 2 pointsGroup = closest.groupByKey() newCenters =pointsGroup.mapValues( ps => average(ps)) d = distance(centers, newCenters) centers = newCenters.map(_) } Feature 1

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**Ease of use Interactive shell:**

Useful for featurization, pre-processing data Lines of code for K-Means Spark ~ 90 lines – (Part of hands-on tutorial !) Hadoop/Mahout ~ 4 files, > 300 lines

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Performance Logistic Regression K-Means [Zaharia et. al, NSDI’12]

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**Conclusion Spark: Framework for cluster computing**

Fast and easy machine learning programs K means clustering using Spark Hands-on exercise this afternoon ! Examples and more:

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