Intro to Mahout -- DC Hadoop

Intro to Apache Mahout
Grant Ingersoll
Lucid Imagination
http://www.lucidimagination.com

Anyone Here Use Machine Learning?
Any users of:
Google?
Search?
Priority Inbox?
Facebook?
Twitter?
LinkedIn?

Topics
Background and Use Cases
What can you do in Mahout?
Where’s the community at?
Resources
K-Means in Hadoop (time permitting)

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

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?

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

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

Sampling of Who uses Mahout?
https://cwiki.apache.org/confluence/display/MAHOUT/Powered+By+Mahout

What Can I do with Mahout Right Now?3C + FPM + O = Mahout

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

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)

Categorization
Place new items into predefined categories:
Sports, politics, entertainment
Recommenders
Implementations
Naïve Bayes (M/R)
Compl. Naïve Bayes (M/R)
Decision Forests (M/R)
Linear Regression (Seq. but Fast!)
See Chapter 17 of Mahout in Action for Shop It To Me use case:
http://awe.sm/5FyNe

Freq. Pattern Mining
Identify frequently co-occurrent items
Useful for:
Query Recommendations
Apple -> iPhone, orange, OS X
Related product placement
Basket Analysis
Map/Reduce
http://www.amazon.com

Other
Primitive Collections!
Collocations (M/R)
Math library
Vectors, Matrices, etc.
Noise Reduction via Singular Value Decomp (M/R)

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

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.

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

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

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

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

K-Means
Clustering Algorithm
Nicely parallelizable!
http://en.wikipedia.org/wiki/K-means_clustering

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)

Map-Reduce Iteration
Each Iteration calculates the Centroids using:
KMeansMapper
KMeansCombiner
KMeansReducer
Clustering Step
Calculate the points for each Centroid using:
KMeansClusterMapper

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

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

KMeansCombiner
Just like KMeansReducer, but only produces partial sum of the cluster based on the data local to the Mapper

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>

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Intro to Mahout -- DC Hadoop

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