Where Search Meets Machine Learning: Presented by Diana Hu & Joaquin Delgado, Verizon
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Lucene/Solr Revolution 2015
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Where Search Meets Machine Learning: Presented by Diana Hu & Joaquin Delgado, Verizon
- 1. Where Search Meets Machine Learning Diana Hu @sdianahu — Data Science Lead, Verizon Joaquin Delgado @joaquind — Director of Engineering, Verizon
- 2. Disclaimer 2 The content of this presentation are of the authors’ personal statements and does not officially represent their employer’s view in anyway. Included content is especially not intended to convey the views of OnCue or Verizon 01
- 3. Index 1. Introduction 2. Search and Information Retrieval 3. ML problems as Search-based Systems 4. ML Meets Search!
- 4. Introduction
- 5. Scaling learning systems is hard! • Millions of users, items • Billions of features • Imbalanced Datasets • Complex Distributed Systems • Many algorithms have not been tested at “Internet Scale”
- 6. Typical approaches • Distributed systems – Fault tolerance, Throughput vs. latency • Parallelization Strategies – Hashing, trees • Processing – Map reduce variants, MPI, graph parallel • Databases – Key/Value Stores, NoSQL Such a custom system requires TLC
- 8. Search Search is about finding specific things that are either known or assumed to exist, Discovery is about is about helping the user encounter what he/she didn’t even know exists. • Focused on Search: Search Engines, Database Systems • Focused on Discovery: Recommender Systems, Advertising Predicate Logic and Declarative Languages Rock!
- 9. Search stack Matched Hits Representation Function Similarity Calculation Matched HitsDocuments Representation Function Input Query Matched HitsMatched HitsRetrieved Documents Online Processing Offline Processing (*)RelevanceFeedback Query Representation Doc Representation Index *Metadata Engineering (*) Optional
- 10. Relevance: Vector Space Model
- 11. Search Engines: the big hammer • Search engines are largely used to solve non-IR search problems, because: • Widely Available • Fast and Scalable • Integrates well with existing data stores
- 12. But… Are we using the right tool? • Search Engines were originally designed for IR. • Complex non-IR search tasks sometimes require a two phase approach Phase1) Filter Phase 2) Rank
- 14. ML problems as Search-based Systems
- 15. Machine Learning Machine Learning in particular supervised learning refer to techniques used to learn how to classify or score previously unseen objects based on a training dataset Inference and Generalization are the Key!
- 17. Learning systems’ stack Visualization / UI Retrieval Ranking Query Generation and Contextual Pre-filtering Model Building Index Building Data/Events Collections Data Analytics Contextual Post Filtering OnlineOffline Experimentation
- 18. Case study: Recommender Systems • Reduce information load by estimating relevance • Ranking (aka Relevance) Approaches: • Collaborative filtering • Content Based • Knowledge Based • Hybrid • Beyond rating prediction and ranking • Business filtering logic • Low latency and Scale
- 19. RecSys: Content based models • Rec Task: Given a user profile find the best matching items by their attributes • Similarity calculation: based on keyword overlap between user/items • Neighborhood method (i.e. nearest neighbor) • Query-based retrieval (i.e. Rocchio’s method) • Probabilistic methods (classical text classification) • Explicit decision models • Feature representation: based on content analysis • Vector space model • TF-IDF • Topic Modeling
- 20. RecSys: Collaborative Filtering Matrix Factorization Rating Dataset User Factors Item Factors Re-Ranking Model Input Query Online Processing Offline Processing Recommendations
- 21. RecSys: Collaborative Filtering Matrix Factorization Rating Dataset User Factors Item Factors Re-Ranking Model Input Query Online Processing Offline Processing Recommendations
- 22. ML Meets Search! ML Search
- 23. Remember the elephant? Visualization / UI Retrieval Ranking Query Generation and Contextual Pre-filtering Model Building Index Building Data/Events Collections Data Analytics Contextual Post Filtering OnlineOffline Experimentation
- 24. Simplifying the stack! Visualization / UI Query Generation and Contextual Pre-filtering Model Building Index Building Data/Events Collections Data Analytics OnlineOffline Experimentation Retrieval Contextual Post Filtering Ranking
- 25. Search stack Matched Hits Representation Function Similarity Calculation Matched HitsDocuments Representation Function Input Query Matched HitsMatched HitsRetrieved Documents Online Processing Offline Processing (*)RelevanceFeedback Query Representation Doc Representation Index *Metadata Engineering (*) Optional
- 26. Simplifying the Search stack Matched Hits Representation Function Similarity Calculation Matched HitsDocuments Representation Function Input Query Matched HitsMatched HitsRetrieved Documents Online Processing Offline Processing (*)RelevanceFeedback Query Representation Doc Representation Index *Metadata Engineering (*) Optional Retrieval Contextual Post Filtering Ranking ML-Scoring Plugin Serialized ML Model
- 27. ML-Scoring architecture Lucene/Solr Instances + Labels Instances Index ML Scoring Plugin Serialized ML Model Online Processing Offline Processing Trainer + Indexer
- 28. ML-Scoring Options • Option A: Solr FunctionQuery • Pro: Model is just a query! • Cons: Limits expressiveness of models • Option B: Solr Custom Function Query • Pro: Loading any type of model (also PMML) • Cons: Memory limitations, also multiple model reloading • Option C: Lucene CustomScoreQuery • Pro: Can use PMML and tune how PMML gets loaded • Cons: No control on matches • Option D: Lucene Low level Custom Query • *Mahout vectors from Lucene text (only trains, so not an option)
- 29. Real-life Problem • Census database that contains documents with the following fields: 1. Age: continuous; 2. Workclass: 8 values; 3. Fnlwgt: continuous.; 4. Education: 16 values; 5. Education-num: continuous.; 6. Marital-status: 7 values; 7. Occupation: 14 values; 8. Relationship: 6 values; 9. Race: 5 values; 10. Sex: Male, Female; 11. Capital-gain: continuous.;12. Capital- loss: continuous.; 13. Hours-per-week: continuous.; 14. Native-country: 41 values; 15. >50K Income: Yes, No. • Task is to predict whether a person makes more than 50k a year based on their attributes
- 30. 1) Learn from the (training) data Naïve Bayes SVM Logistic Regression Decision Trees Train with your favorite ML Framework
- 31. Option A: Just a Solr Function Query q=“sum(C, product(age,w1), product(Workclass,w2), product(Fnlwgt, w3), product(Education, w4), ….)” Serialized ML Model as Query Trainer + Indexer Y_prediction = C + XB
- 32. May result in a crazy Solr functionQuery See more at https://wiki.apache.org/solr/FunctionQuery q=dismax&bf="ord(educaton-num)^0.5 recip(rord(age),1,1000,1000)^0.3"
- 33. What about models like this?
- 34. Option B: Custom Solr FuntionQuery 1. Subclass org.apache.solr.search.ValueSourceParser. public class MyValueSourceParser extends ValueSourceParser { public void init (NamedList namedList) { … } public ValueSource parse(FunctionQParser fqp) throws ParseException { return new MyValueSource(); } } 2. In solrconfig.xml, register your new ValueSourceParser directly under the <config> tag <valueSourceParser name=“myfunc” class=“com.custom.MyValueSourceParser” /> 3. Subclass org.apache.solr.search.ValueSource and instantiate it in ValueSourceParser.parse()
- 35. Option C: Lucene CustomScoreQuery 2C) Serialize model with PMML • Can use JPMML library to read serialized model in Lucene • On Lucene will need to implement an extension with JPMML-evaluator to take vectors as expected 3C) In Lucene: • Override CustomScoreQuery: load PMML • Create CustomScoreProvider: do model PMML data marshaling • Rescoring: PMML evaluation
- 36. Predictive Model Markup Language • Why use PMML • Allows users to build a model in one system • Export model and deploy it in a different environment for prediction • Fast iteration: from research to deployment to production • Model is a XML document with: • Header: description of model, and where it was generated • DataDictionary: defines fields used by model • Model: structure and parameters of model • http://dmg.org/pmml/v4-2-1/GeneralStructure.html
- 37. Example: Train in Spark to PMML import org.apache.spark.mllib.clustering.KMeans import org.apache.spark.mllib.linalg.Vectors // Load and parse the data val data = sc.textFile("/path/to/file") .map(s => Vectors.dense(s.split(',').map(_.toDouble))) // Cluster the data into three classes using KMeans val numIterations = 20 val numClusters = 3 val kmeansModel = KMeans.train(data, numClusters, numIterations) // Export clustering model to PMML kmeansModel.toPMML("/path/to/kmeans.xml")
- 38. PMML XML File
- 39. Overriding scores with CustomScoreQuery CustomScoreProvider CustomScoreQuery Lucene Query Find next Match Score Rescore Doc New Score *Credit to Doug Turnbull’s Hacking Lucene forCustom Search Results
- 40. Overriding scores with CustomScoreQuery • Matching remains • Scoring overridden CustomScoreProvider CustomScoreQuery Lucene Query Find next Match Score Rescore Doc New Score *Credit to Doug Turnbull’s Hacking Lucene forCustom Search Results
- 41. Implementing CustomScoreQuery 1. Given normal Lucene Query, use a CustomScoreQuery to wrap it TermQuery q = New TermQuery(term) MyCustomScoreQuery mcsq = New MyCustomScoreQuery(q) //Make sure query has all fields needed by PMML!
- 42. Implementing CustomScoreQuery 2. Initialize PMML PMML pmml = ...; ModelEvaluatorFactory modelEvaluatorFactory = ModelEvaluatorFactory.newInstance(); ModelEvaluator<?> modelEvaluator = modelEvaluatorFactory.newModelManager(pmml); Evaluator evaluator = (Evaluator)modelEvaluator;
- 43. Implementing CustomScoreQuery 2. Rescore each doc with IndexReader and docID public float customScore(int doc, float subQueryScore, float valSrcScores[]) throws IOException { //Lucene reader IndexReader r = context.reader(); Terms tv = r.getTermVector(doc, _field); TermsEnum tenum = null; tenum = tv.iterator(tenum); //convert the iterator order to fields needed by model TermsEnum tenumPMML = tenum2PMML(tenum, evaluator.getActiveFields());
- 44. Implementing CustomScoreQuery 2. Rescore each doc with IndexReader and docID //Marshall Data into PMML Map<FieldName, FieldValue> arguments = new LinkedHashMap<FieldName, FieldValue>(); List<FieldName> activeFields = evaluator.getActiveFields(); for(FieldName activeField : activeFields){ // The raw is value has been sorted with number of fields needed Object rawValue = tenumPMML.next; FieldValue activeValue = evaluator.prepare(activeField, rawValue); arguments.put(activeField, activeValue); }
- 45. Implementing CustomScoreQuery 2. Rescore each doc with IndexReader and docID //Rescore and evaluate with PMML Map<FieldName, ?> results = evaluator.evaluate(arguments); FieldName targetName = evaluator.getTargetField(); Object targetValue = results.get(targetName); return (float) targetValue;
- 46. Potential issues • Performance • If search space is very large • If model complexity explodes (i.e. kernel expansion) • Operations • Code is running on key infrastructure • Versioning • Binary Compatibility
- 47. Option D: Low Level Lucene • CustomScoreQuery or Custom FunctionScore can’t control matches • If you want custom matches and scoring…. • Implement: • Custom Query Class • Custom Weight Class • Custom Scorer Class • http://opensourceconnections.com/blog/2014/03/12/using- customscorequery-for-custom-solrlucene-scoring/
- 48. Conclusion • Importance of the full picture – Learning systems from the lenses of the whole elephant • Reducing the time from science to production is complicated • Scalability is hard! • Why not have ML use Search in its core during online eval? • Solr and Lucene are a start to customize your learning system
- 49. We are Hiring! Contact me at diana.hu@verizon.com @sdianahu Q&A
- 50. O C T O B E R 1 3 - 1 6 , 2 0 1 6 • A U S T I N , T X