Lightweight python wrapper for vowpal_wabbit.
Why: Scalable, blazingly fast machine learning.
- Install vowpal_wabbit. Clone and run
- Install cython.
pip install cython
- Clone vowpal_porpoise
python setup.py installto install.
Now can you do:
import vowpal_porpoise from python.
Linear regression with l1 penalty:
from vowpal_porpoise import VW # Initialize the model vw = VW(moniker='test', # a name for the model passes=10, # vw arg: passes loss='quadratic', # vw arg: loss learning_rate=10, # vw arg: learning_rate l1=0.01) # vw arg: l1 # Inside the with training() block a vw process will be # open to communication with vw.training(): for instance in ['1 |big red square',\ '0 |small blue circle']: vw.push_instance(instance) # here stdin will close # here the vw process will have finished # Inside the with predicting() block we can stream instances and # acquire their labels with vw.predicting(): for instance in ['1 |large burnt sienna rhombus',\ '0 |little teal oval']: vw.push_instance(instance) # Read the predictions like this: predictions = list(vw.read_predictions_())
L-BFGS with a rank-5 approximation:
from vowpal_porpoise import VW # Initialize the model vw = VW(moniker='test_lbfgs', # a name for the model passes=10, # vw arg: passes lbfgs=True, # turn on lbfgs mem=5) # lbfgs rank
Latent Dirichlet Allocation with 100 topics:
from vowpal_porpoise import VW # Initialize the model vw = VW(moniker='test_lda', # a name for the model passes=10, # vw arg: passes lda=100, # turn on lda minibatch=100) # set the minibatch size
vowpal_porpoise also ships with an interface into scikit-learn, which allows awesome experiment-level stuff like cross-validation:
from sklearn.cross_validation import StratifiedKFold from sklearn.grid_search import GridSearchCV from vowpal_porpoise.sklearn import VW_Classifier GridSearchCV( VW_Classifier(loss='logistic', moniker='example_sklearn', passes=10, silent=True, learning_rate=10), param_grid=parameters, score_func=f1_score, cv=StratifiedKFold(y_train), ).fit(X_train, y_train)
Check out example_sklearn.py for more details
Library Interace (DISABLED as of 2013-08-12)
with vw.predicting_library(): for instance in ['1 |large burnt sienna rhombus', \ '1 |little teal oval']: prediction = vw.push_instance(instance)
Now the predictions are returned directly to the parent process, rather than having to read from disk.
examples/example1.py for more details.
Alternatively you can use the raw library interface:
import vw_c vw = vw_c.VW("--loss=quadratic --l1=0.01 -f model") vw.learn("1 |this is a positive example") vw.learn("0 |this is a negative example") vw.finish()
Currently does not support passes due to some limitations in the underlying vw C code.
Need more examples?
- example1.py: SimpleModel class wrapper around VP (both standard and library flavors)
- example_library.py: Demonstrates the low-level vw library wrapper, classifying lines of alice in wonderland vs through the looking glass.
vowpal_wabbit is insanely
fast and scalable. vowpal_porpoise is slower, but only during the
initial training pass. Once the data has been properly cached it will idle while vowpal_wabbit does all the heavy lifting.
Furthermore, vowpal_porpoise was designed to be lightweight and not to get in the way
of vowpal_wabbit's scalability, e.g. it allows distributed learning via
--nodes and does not require data to be batched in memory. In our
research work we use vowpal_porpoise on an 80-node cluster running over multiple
terabytes of data.
The main benefit of vowpal_porpoise is allowing rapid prototyping of new
models and feature extractors. We found that we had been doing this in an
ad-hoc way using python scripts to shuffle around massive gzipped text files,
so we just closed the loop and made vowpal_wabbit a python library.
How it works
Wraps the vw binary in a subprocess and uses stdin to push data, temporary
files to pull predictions. Why not use the prediction labels vw provides on stdout? It
turns out that the python GIL basically makes streamining in and out of a
process (even asynchronously) painfully difficult. If you know of a clever way
to get around this, please email me. In other languages (e.g. in a forthcoming
scala wrapper) this is not an issue.
Alternatively, you can use a pure api call (
vw_c, wrapping libvw) for prediction.
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