Intro to Mahout -- DC Hadoop
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Introduction to Apache Mahout -- talk given at DC Hadoop Meetup on April 28
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Intro to Mahout -- DC Hadoop
- 1. Intro to Apache Mahout Grant Ingersoll Lucid Imagination http://www.lucidimagination.com
- 2. Anyone Here Use Machine Learning? Any users of: Google? Search? Priority Inbox? Facebook? Twitter? LinkedIn?
- 3. Topics Background and Use Cases What can you do in Mahout? Where’s the community at? Resources K-Means in Hadoop (time permitting)
- 4. Definition “Machine Learning is programming computers to optimize a performance criterion using example data or past experience” Intro. To Machine Learning by E. Alpaydin Subset of Artificial Intelligence Lots of related fields: Information Retrieval Stats Biology Linear algebra Many more
- 5. Common Use Cases Recommend friends/dates/products Classify content into predefined groups Find similar content Find associations/patterns in actions/behaviors Identify key topics/summarize text Documents and Corpora Detect anomalies/fraud Ranking search results Others?
- 6. Apache Mahout An Apache Software Foundation project to create scalable machine learning libraries under the Apache Software License http://mahout.apache.org Why Mahout? Many Open Source ML libraries either: Lack Community Lack Documentation and Examples Lack Scalability Lack the Apache License Or are research-oriented Definition:http://dictionary.reference.com/browse/mahout
- 7. What does scalable mean to us? Goal: Be as fast and efficient as possible given the intrinsic design of the algorithm Some algorithms won’t scale to massive machine clusters Others fit logically on a Map Reduce framework like Apache Hadoop Still others will need different distributed programming models Others are already fast (SGD) Be pragmatic
- 8. Sampling of Who uses Mahout? https://cwiki.apache.org/confluence/display/MAHOUT/Powered+By+Mahout
- 9. What Can I do with Mahout Right Now?3C + FPM + O = Mahout
- 10. Collaborative Filtering Extensive framework for collaborative filtering (recommenders) Recommenders User based Item based Online and Offline support Offline can utilize Hadoop Many different Similarity measures Cosine, LLR, Tanimoto, Pearson, others
- 11. Clustering Document level Group documents based on a notion of similarity K-Means, Fuzzy K-Means, Dirichlet, Canopy, Mean-Shift, EigenCuts (Spectral) All Map/Reduce Distance Measures Manhattan, Euclidean, other Topic Modeling Cluster words across documents to identify topics Latent Dirichlet Allocation (M/R)
- 14. Other Primitive Collections! Collocations (M/R) Math library Vectors, Matrices, etc. Noise Reduction via Singular Value Decomp (M/R)
- 15. Prepare Data from Raw content Data Sources: Lucene integration bin/mahout lucene.vector… Document Vectorizer bin/mahout seqdirectory … bin/mahout seq2sparse … Programmatically See the Utils module in Mahout and the Iterator<Vector> classes Database File system
- 16. How to: Command Line Most algorithms have a Driver program $MAHOUT_HOME/bin/mahout.shhelps with most tasks Prepare the Data Different algorithms require different setup Run the algorithm Single Node Hadoop Print out the results or incorporate into application Several helper classes: LDAPrintTopics, ClusterDumper, etc.
- 17. What’s Happening Now? Unified Framework for Clustering and Classification 0.5 release on the horizon (May?) Working towards 1.0 release by focusing on: Tests, examples, documentation API cleanup and consistency Gearing up for Google Summer of Code New M/R work for Hidden Markov Models
- 18. Summary Machine learning is all over the web today Mahout is about scalable machine learning Mahout has functionality for many of today’s common machine learning tasks Many Mahout implementations use Hadoop
- 19. Resources http://mahout.apache.org http://cwiki.apache.org/MAHOUT {user|dev}@mahout.apache.org http://svn.apache.org/repos/asf/mahout/trunk http://hadoop.apache.org
- 20. Resources “Mahout in Action” Owen, Anil, Dunning and Friedman http://awe.sm/5FyNe “Introducing Apache Mahout” http://www.ibm.com/developerworks/java/library/j-mahout/ “Taming Text” by Ingersoll, Morton, Farris “Programming Collective Intelligence” by Toby Segaran “Data Mining - Practical Machine Learning Tools and Techniques” by Ian H. Witten and Eibe Frank “Data-Intensive Text Processing with MapReduce” by Jimmy Lin and Chris Dyer
- 21. K-Means Clustering Algorithm Nicely parallelizable! http://en.wikipedia.org/wiki/K-means_clustering
- 22. K-Means in Map-Reduce Input: Mahout Vectors representing the original content Either: A predefined set of initial centroids (Can be from Canopy) --k – The number of clusters to produce Iterate Do the centroid calculation (more in a moment) Clustering Step (optional) Output Centroids (as Mahout Vectors) Points for each Centroid (if Clustering Step was taken)
- 23. Map-Reduce Iteration Each Iteration calculates the Centroids using: KMeansMapper KMeansCombiner KMeansReducer Clustering Step Calculate the points for each Centroid using: KMeansClusterMapper
- 24. KMeansMapper During Setup: Load the initial Centroids (or the Centroids from the last iteration) Map Phase For each input Calculate it’s distance from each Centroid and output the closest one Distance Measures are pluggable Manhattan, Euclidean, Squared Euclidean, Cosine, others
- 25. KMeansReducer Setup: Load up clusters Convergence information Partial sums from KMeansCombiner (more in a moment) Reduce Phase Sum all the vectors in the cluster to produce a new Centroid Check for Convergence Output cluster
- 26. KMeansCombiner Just like KMeansReducer, but only produces partial sum of the cluster based on the data local to the Mapper
- 27. KMeansClusterMapper Some applications only care about what the Centroids are, so this step is optional Setup: Load up the clusters and the DistanceMeasure used Map Phase Calculate which Cluster the point belongs to Output <ClusterId, Vector>
Editor's Notes
- 3C: The three C’s: clustering, classification and collaborative filteringFPM: Frequent patternset miningO: Other (math, collections, etc.)
- Convergence just checks to see how far the centroid has moved from the previous centroid