# Vowpal Wabbit

Vowpal Wabbit (also known as "VW") is an open-source fast out-of-core machine learning system library and program developed originally at Yahoo! Research, and currently at Microsoft Research.wikipedia

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### John Langford (computer scientist)

**John Langford**

It was started and is led by John Langford.

He is the author of the weblog hunch.net and the principal developer of Vowpal Wabbit.

### Online machine learning

**online learningon-line learningonline**

Vowpal Wabbit is notable as an efficient scalable implementation of online machine learning with support for a number of machine learning reductions, importance weighting, and a selection of different loss functions and optimization algorithms.

### Stochastic gradient descent

**AdaGradAdaptive Moment Estimationgradient-based learning methods**

Stochastic gradient descent is a popular algorithm for training a wide range of models in machine learning, including (linear) support vector machines, logistic regression (see, e.g., Vowpal Wabbit) and graphical models.

### Feature hashing

**Hashing trickhash trickHashing-Trick**

### MurmurHash

It has been adopted into a number of open-source projects, most notably libstdc++ (ver 4.6), nginx (ver 1.0.1), Rubinius, libmemcached (the C driver for Memcached), npm (nodejs package manager), maatkit, Hadoop, Kyoto Cabinet, RaptorDB, OlegDB, Cassandra, Solr, vowpal wabbit, Elasticsearch, Guava, Kafka and RedHat Virtual Data Optimizer (VDO) [ ]

### Open-source software

**open sourceopen-sourceopen source software**

Vowpal Wabbit (also known as "VW") is an open-source fast out-of-core machine learning system library and program developed originally at Yahoo! Research, and currently at Microsoft Research.

### External memory algorithm

**out-of-coreexternal memoryexternal memory model**

Vowpal Wabbit (also known as "VW") is an open-source fast out-of-core machine learning system library and program developed originally at Yahoo! Research, and currently at Microsoft Research.

### Machine learning

**machine-learninglearningstatistical learning**

Vowpal Wabbit (also known as "VW") is an open-source fast out-of-core machine learning system library and program developed originally at Yahoo! Research, and currently at Microsoft Research.

### Yahoo! Research

**Yahoo!**

### Microsoft Research

**Microsoft Research CambridgeMicrosoft Research New EnglandMicrosoft Station Q**

### Reduction (complexity)

**reductionreducedreductions**

Vowpal Wabbit is notable as an efficient scalable implementation of online machine learning with support for a number of machine learning reductions, importance weighting, and a selection of different loss functions and optimization algorithms.

### Loss function

**objective functioncost functionrisk function**

Vowpal Wabbit is notable as an efficient scalable implementation of online machine learning with support for a number of machine learning reductions, importance weighting, and a selection of different loss functions and optimization algorithms.

### Active learning (machine learning)

**Active learningactive or query learning**

### Ordinary least squares

**OLSleast squaresOrdinary least squares regression**

### Matrix decomposition

**matrix factorizationdecompositionfactorization**

### Artificial neural network

**artificial neural networksneural networksneural network**

### Multi-armed bandit

**Bandit problemContextual-banditdueling bandit problems**

### Broyden–Fletcher–Goldfarb–Shanno algorithm

**BFGSBFGS methodBroyden-Fletcher-Goldfarb-Shanno (BFGS) method**

### Conjugate gradient method

**conjugate gradientpreconditioned conjugate gradient methodconjugate gradient descent**

### Taxicab geometry

**Manhattan distanceL1 normtaxicab metric**

### Norm (mathematics)

**normEuclidean normseminorm**

### Elastic net regularization

**elastic netelastic net regularized regressionElastic nets**

### N-gram

**n''-gramunigramn-grams**

### Hyperparameter optimization

**hyperparameterHyperparameter grid searchSweeping through the parameter space**