# -*- coding: utf-8 -*-
# @Time : 2020/9/21
# @Author : Jingsen Zhang
# @Email : zhangjingsen@ruc.edu.cn
# UPDATE
# @Time : 2020/10/2
# @Author : Jingsen Zhang
# @Email : zhangjingsen@ruc.edu.cn
r"""
Caser
################################################
Reference:
Jiaxi Tang et al., "Personalized Top-N Sequential Recommendation via Convolutional Sequence Embedding" in WSDM 2018.
Reference code:
https://github.com/graytowne/caser_pytorch
"""
import torch
from torch import nn
from torch.nn import functional as F
from torch.nn.init import normal_, xavier_normal_, constant_
from recbole.model.abstract_recommender import SequentialRecommender
from recbole.model.loss import RegLoss, BPRLoss
[docs]class Caser(SequentialRecommender):
r"""Caser is a model that incorporate CNN for recommendation.
Note:
We did not use the sliding window to generate training instances as in the paper, in order that
the generation method we used is common to other sequential models.
For comparison with other models, we set the parameter T in the paper as 1.
In addition, to prevent excessive CNN layers (ValueError: Training loss is nan), please make sure the parameters MAX_ITEM_LIST_LENGTH small, such as 10.
"""
def __init__(self, config, dataset):
super(Caser, self).__init__(config, dataset)
# load parameters info
self.embedding_size = config['embedding_size']
self.loss_type = config['loss_type']
self.n_h = config['nh']
self.n_v = config['nv']
self.dropout_prob = config['dropout_prob']
self.reg_weight = config['reg_weight']
# load dataset info
self.n_users = dataset.user_num
# define layers and loss
self.user_embedding = nn.Embedding(self.n_users, self.embedding_size, padding_idx=0)
self.item_embedding = nn.Embedding(self.n_items, self.embedding_size, padding_idx=0)
# vertical conv layer
self.conv_v = nn.Conv2d(in_channels=1, out_channels=self.n_v, kernel_size=(self.max_seq_length, 1))
# horizontal conv layer
lengths = [i + 1 for i in range(self.max_seq_length)]
self.conv_h = nn.ModuleList([
nn.Conv2d(in_channels=1, out_channels=self.n_h, kernel_size=(i, self.embedding_size)) for i in lengths
])
# fully-connected layer
self.fc1_dim_v = self.n_v * self.embedding_size
self.fc1_dim_h = self.n_h * len(lengths)
fc1_dim_in = self.fc1_dim_v + self.fc1_dim_h
self.fc1 = nn.Linear(fc1_dim_in, self.embedding_size)
self.fc2 = nn.Linear(self.embedding_size + self.embedding_size, self.embedding_size)
self.dropout = nn.Dropout(self.dropout_prob)
self.ac_conv = nn.ReLU()
self.ac_fc = nn.ReLU()
self.reg_loss = RegLoss()
if self.loss_type == 'BPR':
self.loss_fct = BPRLoss()
elif self.loss_type == 'CE':
self.loss_fct = nn.CrossEntropyLoss()
else:
raise NotImplementedError("Make sure 'loss_type' in ['BPR', 'CE']!")
# parameters initialization
self.apply(self._init_weights)
def _init_weights(self, module):
if isinstance(module, nn.Embedding):
normal_(module.weight.data, 0, 1.0 / module.embedding_dim)
elif isinstance(module, nn.Linear):
xavier_normal_(module.weight.data)
if module.bias is not None:
constant_(module.bias.data, 0)
[docs] def forward(self, user, item_seq):
# Embedding Look-up
# use unsqueeze() to get a 4-D input for convolution layers. (batch_size * 1 * max_length * embedding_size)
item_seq_emb = self.item_embedding(item_seq).unsqueeze(1)
user_emb = self.user_embedding(user).squeeze(1)
# Convolutional Layers
out, out_h, out_v = None, None, None
# vertical conv layer
if self.n_v:
out_v = self.conv_v(item_seq_emb)
out_v = out_v.view(-1, self.fc1_dim_v) # prepare for fully connect
# horizontal conv layer
out_hs = list()
if self.n_h:
for conv in self.conv_h:
conv_out = self.ac_conv(conv(item_seq_emb).squeeze(3))
pool_out = F.max_pool1d(conv_out, conv_out.size(2)).squeeze(2)
out_hs.append(pool_out)
out_h = torch.cat(out_hs, 1) # prepare for fully connect
# Fully-connected Layers
out = torch.cat([out_v, out_h], 1)
# apply dropout
out = self.dropout(out)
# fully-connected layer
z = self.ac_fc(self.fc1(out))
x = torch.cat([z, user_emb], 1)
seq_output = self.ac_fc(self.fc2(x))
# the hidden_state of the predicted item, size:(batch_size * hidden_size)
return seq_output
[docs] def reg_loss_conv_h(self):
r"""
L2 loss on conv_h
"""
loss_conv_h = 0
for name, parm in self.conv_h.named_parameters():
if name.endswith('weight'):
loss_conv_h = loss_conv_h + loss_conv_h * parm.norm(2)
return self.reg_weight * loss_conv_h
[docs] def calculate_loss(self, interaction):
item_seq = interaction[self.ITEM_SEQ]
user = interaction[self.USER_ID]
seq_output = self.forward(user, item_seq)
pos_items = interaction[self.POS_ITEM_ID]
if self.loss_type == 'BPR':
neg_items = interaction[self.NEG_ITEM_ID]
pos_items_emb = self.item_embedding(pos_items)
neg_items_emb = self.item_embedding(neg_items)
pos_score = torch.sum(seq_output * pos_items_emb, dim=-1) # [B]
neg_score = torch.sum(seq_output * neg_items_emb, dim=-1) # [B]
loss = self.loss_fct(pos_score, neg_score)
else: # self.loss_type = 'CE'
test_item_emb = self.item_embedding.weight
logits = torch.matmul(seq_output, test_item_emb.transpose(0, 1))
loss = self.loss_fct(logits, pos_items)
reg_loss = self.reg_loss([
self.user_embedding.weight, self.item_embedding.weight, self.conv_v.weight, self.fc1.weight, self.fc2.weight
])
loss = loss + self.reg_weight * reg_loss + self.reg_loss_conv_h()
return loss
[docs] def predict(self, interaction):
item_seq = interaction[self.ITEM_SEQ]
user = interaction[self.USER_ID]
test_item = interaction[self.ITEM_ID]
seq_output = self.forward(user, item_seq)
test_item_emb = self.item_embedding(test_item)
scores = torch.mul(seq_output, test_item_emb).sum(dim=1) # [B]
return scores
[docs] def full_sort_predict(self, interaction):
item_seq = interaction[self.ITEM_SEQ]
user = interaction[self.USER_ID]
seq_output = self.forward(user, item_seq)
test_items_emb = self.item_embedding.weight
scores = torch.matmul(seq_output, test_items_emb.transpose(0, 1)) # [B, n_items]
return scores