# Copyright 2018 The Cornac Authors. All Rights Reserved.
#
# Licensed 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
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ============================================================================
import numpy as np
from .recom_ncf_base import NCFBase
from ...exception import ScoreException
[docs]
class GMF(NCFBase):
"""Generalized Matrix Factorization.
Parameters
----------
num_factors: int, optional, default: 8
Embedding size of MF model.
reg: float, optional, default: 0.
Regularization (weight_decay).
num_epochs: int, optional, default: 20
Number of epochs.
batch_size: int, optional, default: 256
Batch size.
num_neg: int, optional, default: 4
Number of negative instances to pair with a positive instance.
lr: float, optional, default: 0.001
Learning rate.
learner: str, optional, default: 'adam'
Specify an optimizer: adagrad, adam, rmsprop, sgd
backend: str, optional, default: 'tensorflow'
Backend used for model training: tensorflow, pytorch
early_stopping: {min_delta: float, patience: int}, optional, default: None
If `None`, no early stopping. Meaning of the arguments:
- `min_delta`: the minimum increase in monitored value on validation set to be considered as improvement, \
i.e. an increment of less than min_delta will count as no improvement.
- `patience`: number of epochs with no improvement after which training should be stopped.
name: string, optional, default: 'GMF'
Name of the recommender model.
trainable: boolean, optional, default: True
When False, the model is not trained and Cornac assumes that the model is already \
pre-trained.
verbose: boolean, optional, default: False
When True, some running logs are displayed.
seed: int, optional, default: None
Random seed for parameters initialization.
References
----------
* He, X., Liao, L., Zhang, H., Nie, L., Hu, X., & Chua, T. S. (2017, April). Neural collaborative filtering. \
In Proceedings of the 26th international conference on world wide web (pp. 173-182).
"""
def __init__(
self,
name="GMF",
num_factors=8,
reg=0.0,
num_epochs=20,
batch_size=256,
num_neg=4,
lr=0.001,
learner="adam",
backend="tensorflow",
early_stopping=None,
trainable=True,
verbose=True,
seed=None,
):
super().__init__(
name=name,
trainable=trainable,
verbose=verbose,
num_epochs=num_epochs,
batch_size=batch_size,
num_neg=num_neg,
lr=lr,
learner=learner,
backend=backend,
early_stopping=early_stopping,
seed=seed,
)
self.num_factors = num_factors
self.reg = reg
########################
## TensorFlow backend ##
########################
def _build_model_tf(self):
import tensorflow as tf
from .backend_tf import GMFLayer
# Define inputs
user_input = tf.keras.layers.Input(shape=(1,), dtype=tf.int32, name="user_input")
item_input = tf.keras.layers.Input(shape=(1,), dtype=tf.int32, name="item_input")
# GMF layer
gmf_layer = GMFLayer(
num_users=self.num_users,
num_items=self.num_items,
emb_size=self.num_factors,
reg_user=self.reg,
reg_item=self.reg,
seed=self.seed,
name="gmf_layer"
)
# Get embeddings and element-wise product
gmf_vector = gmf_layer([user_input, item_input])
# Output layer
logits = tf.keras.layers.Dense(
1,
kernel_initializer=tf.keras.initializers.LecunUniform(seed=self.seed),
name="logits"
)(gmf_vector)
prediction = tf.keras.layers.Activation('sigmoid', name="prediction")(logits)
# Create model with both logits and prediction outputs
model = tf.keras.Model(
inputs=[user_input, item_input],
outputs=prediction,
name="GMF"
)
return model
#####################
## PyTorch backend ##
#####################
def _build_model_pt(self):
from .backend_pt import GMF
return GMF(self.num_users, self.num_items, self.num_factors)
def _score_pt(self, user_idx, item_idx):
import torch
with torch.no_grad():
users = torch.tensor(user_idx).unsqueeze(0).to(self.device)
items = (
torch.from_numpy(np.arange(self.num_items))
if item_idx is None
else torch.tensor(item_idx).unsqueeze(0)
).to(self.device)
output = self.model(users, items)
return output.squeeze().cpu().numpy()
