Source code for fastFM.bpr
# Author: Immanuel Bayer
# License: BSD 3 clause
import ffm
import numpy as np
from .base import FactorizationMachine
from sklearn.utils.testing import assert_array_equal
from .validation import check_array, assert_all_finite
[docs]class FMRecommender(FactorizationMachine):
""" Factorization Machine Recommender with pairwise (BPR) loss solver.
Parameters
----------
n_iter : int, optional
The number of interations of individual samples .
init_stdev: float, optional
Sets the stdev for the initialization of the parameter
random_state: int, optional
The seed of the pseudo random number generator that
initializes the parameters and mcmc chain.
rank: int
The rank of the factorization used for the second order interactions.
l2_reg_w : float
L2 penalty weight for linear coefficients.
l2_reg_V : float
L2 penalty weight for pairwise coefficients.
l2_reg : float
L2 penalty weight for all coefficients (default=0).
step_size : float
Stepsize for the SGD solver, the solver uses a fixed step size and
might require a tunning of the number of iterations `n_iter`.
Attributes
---------
w0_ : float
bias term
w_ : float | array, shape = (n_features)
Coefficients for linear combination.
V_ : float | array, shape = (rank_pair, n_features)
Coefficients of second order factor matrix.
"""
def __init__(self, n_iter=100, init_stdev=0.1, rank=8, random_state=123,
l2_reg_w=0.1, l2_reg_V=0.1, l2_reg=0, step_size=0.1):
super(FMRecommender, self).\
__init__(n_iter=n_iter, init_stdev=init_stdev, rank=rank,
random_state=random_state)
if (l2_reg != 0):
self.l2_reg_V = l2_reg
self.l2_reg_w = l2_reg
else:
self.l2_reg_w = l2_reg_w
self.l2_reg_V = l2_reg_V
self.step_size = step_size
self.task = "ranking"
[docs] def fit(self, X, pairs):
""" Fit model with specified loss.
Parameters
----------
X : scipy.sparse.csc_matrix, (n_samples, n_features)
y : float | ndarray, shape = (n_compares, 2)
Each row `i` defines a pair of samples such that
the first returns a high value then the second
FM(X[i,0]) > FM(X[i, 1]).
"""
# The sgd solver expects a transposed design matrix in column major
# order (csc_matrix).
X = X.T # creates a copy
X = check_array(X, accept_sparse="csc", dtype=np.float64)
assert_all_finite(pairs)
pairs = pairs.astype(np.float64)
# check that pairs contain no real values
assert_array_equal(pairs, pairs.astype(np.int32))
assert pairs.max() <= X.shape[1]
assert pairs.min() >= 0
self.w0_, self.w_, self.V_ = ffm.ffm_fit_sgd_bpr(self, X, pairs)
return self