recommendation.py

#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
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#    http://www.apache.org/licenses/LICENSE-2.0
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import array
from collections import namedtuple

from pyspark import SparkContext, since
from pyspark.rdd import RDD
from pyspark.mllib.common import JavaModelWrapper, callMLlibFunc, inherit_doc
from pyspark.mllib.util import JavaLoader, JavaSaveable
from pyspark.sql import DataFrame

__all__ = ['MatrixFactorizationModel', 'ALS', 'Rating']


class Rating(namedtuple("Rating", ["user", "product", "rating"])):
    """
    Represents a (user, product, rating) tuple.

    >>> r = Rating(1, 2, 5.0)
    >>> (r.user, r.product, r.rating)
    (1, 2, 5.0)
    >>> (r[0], r[1], r[2])
    (1, 2, 5.0)

    .. versionadded:: 1.2.0
    """

    def __reduce__(self):
        return Rating, (int(self.user), int(self.product), float(self.rating))


@inherit_doc
class MatrixFactorizationModel(JavaModelWrapper, JavaSaveable, JavaLoader):

    """A matrix factorisation model trained by regularized alternating
    least-squares.

    >>> r1 = (1, 1, 1.0)
    >>> r2 = (1, 2, 2.0)
    >>> r3 = (2, 1, 2.0)
    >>> ratings = sc.parallelize([r1, r2, r3])
    >>> model = ALS.trainImplicit(ratings, 1, seed=10)
    >>> model.predict(2, 2)
    0.4...

    >>> testset = sc.parallelize([(1, 2), (1, 1)])
    >>> model = ALS.train(ratings, 2, seed=0)
    >>> model.predictAll(testset).collect()
    [Rating(user=1, product=1, rating=1.0...), Rating(user=1, product=2, rating=1.9...)]

    >>> model = ALS.train(ratings, 4, seed=10)
    >>> model.userFeatures().collect()
    [(1, array('d', [...])), (2, array('d', [...]))]

    >>> model.recommendUsers(1, 2)
    [Rating(user=2, product=1, rating=1.9...), Rating(user=1, product=1, rating=1.0...)]
    >>> model.recommendProducts(1, 2)
    [Rating(user=1, product=2, rating=1.9...), Rating(user=1, product=1, rating=1.0...)]
    >>> model.rank
    4

    >>> first_user = model.userFeatures().take(1)[0]
    >>> latents = first_user[1]
    >>> len(latents)
    4

    >>> model.productFeatures().collect()
    [(1, array('d', [...])), (2, array('d', [...]))]

    >>> first_product = model.productFeatures().take(1)[0]
    >>> latents = first_product[1]
    >>> len(latents)
    4

    >>> products_for_users = model.recommendProductsForUsers(1).collect()
    >>> len(products_for_users)
    2
    >>> products_for_users[0]
    (1, (Rating(user=1, product=2, rating=...),))

    >>> users_for_products = model.recommendUsersForProducts(1).collect()
    >>> len(users_for_products)
    2
    >>> users_for_products[0]
    (1, (Rating(user=2, product=1, rating=...),))

    >>> model = ALS.train(ratings, 1, nonnegative=True, seed=10)
    >>> model.predict(2, 2)
    3.8...

    >>> df = sqlContext.createDataFrame([Rating(1, 1, 1.0), Rating(1, 2, 2.0), Rating(2, 1, 2.0)])
    >>> model = ALS.train(df, 1, nonnegative=True, seed=10)
    >>> model.predict(2, 2)
    3.8...

    >>> model = ALS.trainImplicit(ratings, 1, nonnegative=True, seed=10)
    >>> model.predict(2, 2)
    0.4...

    >>> import os, tempfile
    >>> path = tempfile.mkdtemp()
    >>> model.save(sc, path)
    >>> sameModel = MatrixFactorizationModel.load(sc, path)
    >>> sameModel.predict(2, 2)
    0.4...
    >>> sameModel.predictAll(testset).collect()
    [Rating(...
    >>> from shutil import rmtree
    >>> try:
    ...     rmtree(path)
    ... except OSError:
    ...     pass

    .. versionadded:: 0.9.0
    """
    @since("0.9.0")
    def predict(self, user, product):
        """
        Predicts rating for the given user and product.
        """
        return self._java_model.predict(int(user), int(product))

    @since("0.9.0")
    def predictAll(self, user_product):
        """
        Returns a list of predicted ratings for input user and product pairs.
        """
        assert isinstance(user_product, RDD), "user_product should be RDD of (user, product)"
        first = user_product.first()
        assert len(first) == 2, "user_product should be RDD of (user, product)"
        user_product = user_product.map(lambda u_p: (int(u_p[0]), int(u_p[1])))
        return self.call("predict", user_product)

    @since("1.2.0")
    def userFeatures(self):
        """
        Returns a paired RDD, where the first element is the user and the
        second is an array of features corresponding to that user.
        """
        return self.call("getUserFeatures").mapValues(lambda v: array.array('d', v))

    @since("1.2.0")
    def productFeatures(self):
        """
        Returns a paired RDD, where the first element is the product and the
        second is an array of features corresponding to that product.
        """
        return self.call("getProductFeatures").mapValues(lambda v: array.array('d', v))

    @since("1.4.0")
    def recommendUsers(self, product, num):
        """
        Recommends the top "num" number of users for a given product and returns a list
        of Rating objects sorted by the predicted rating in descending order.
        """
        return list(self.call("recommendUsers", product, num))

    @since("1.4.0")
    def recommendProducts(self, user, num):
        """
        Recommends the top "num" number of products for a given user and returns a list
        of Rating objects sorted by the predicted rating in descending order.
        """
        return list(self.call("recommendProducts", user, num))

    def recommendProductsForUsers(self, num):
        """
        Recommends top "num" products for all users. The number returned may be less than this.
        """
        return self.call("wrappedRecommendProductsForUsers", num)

    def recommendUsersForProducts(self, num):
        """
        Recommends top "num" users for all products. The number returned may be less than this.
        """
        return self.call("wrappedRecommendUsersForProducts", num)

    @property
    @since("1.4.0")
    def rank(self):
        """Rank for the features in this model"""
        return self.call("rank")

    @classmethod
    @since("1.3.1")
    def load(cls, sc, path):
        """Load a model from the given path"""
        model = cls._load_java(sc, path)
        wrapper = sc._jvm.MatrixFactorizationModelWrapper(model)
        return MatrixFactorizationModel(wrapper)


class ALS(object):
    """Alternating Least Squares matrix factorization

    .. versionadded:: 0.9.0
    """

    @classmethod
    def _prepare(cls, ratings):
        if isinstance(ratings, RDD):
            pass
        elif isinstance(ratings, DataFrame):
            ratings = ratings.rdd
        else:
            raise TypeError("Ratings should be represented by either an RDD or a DataFrame, "
                            "but got %s." % type(ratings))
        first = ratings.first()
        if isinstance(first, Rating):
            pass
        elif isinstance(first, (tuple, list)):
            ratings = ratings.map(lambda x: Rating(*x))
        else:
            raise TypeError("Expect a Rating or a tuple/list, but got %s." % type(first))
        return ratings

    @classmethod
    @since("0.9.0")
    def train(cls, ratings, rank, iterations=5, lambda_=0.01, blocks=-1, nonnegative=False,
              seed=None):
        """
        Train a matrix factorization model given an RDD of ratings given by users to some products,
        in the form of (userID, productID, rating) pairs. We approximate the ratings matrix as the
        product of two lower-rank matrices of a given rank (number of features). To solve for these
        features, we run a given number of iterations of ALS. This is done using a level of
        parallelism given by `blocks`.
        """
        model = callMLlibFunc("trainALSModel", cls._prepare(ratings), rank, iterations,
                              lambda_, blocks, nonnegative, seed)
        return MatrixFactorizationModel(model)

    @classmethod
    @since("0.9.0")
    def trainImplicit(cls, ratings, rank, iterations=5, lambda_=0.01, blocks=-1, alpha=0.01,
                      nonnegative=False, seed=None):
        """
        Train a matrix factorization model given an RDD of 'implicit preferences' given by users
        to some products, in the form of (userID, productID, preference) pairs. We approximate the
        ratings matrix as the product of two lower-rank matrices of a given rank (number of
        features).  To solve for these features, we run a given number of iterations of ALS.
        This is done using a level of parallelism given by `blocks`.
        """
        model = callMLlibFunc("trainImplicitALSModel", cls._prepare(ratings), rank,
                              iterations, lambda_, blocks, alpha, nonnegative, seed)
        return MatrixFactorizationModel(model)


def _test():
    import doctest
    import pyspark.mllib.recommendation
    from pyspark.sql import SQLContext
    globs = pyspark.mllib.recommendation.__dict__.copy()
    sc = SparkContext('local[4]', 'PythonTest')
    globs['sc'] = sc
    globs['sqlContext'] = SQLContext(sc)
    (failure_count, test_count) = doctest.testmod(globs=globs, optionflags=doctest.ELLIPSIS)
    globs['sc'].stop()
    if failure_count:
        exit(-1)


if __name__ == "__main__":
    _test()