Source code for recbole.model.sequential_recommender.s3rec

# -*- coding: utf-8 -*-
# @Time    : 2020/9/19 21:49
# @Author  : Hui Wang
# @Email   : hui.wang@ruc.edu.cn

r"""
S3Rec
################################################

Reference:
    Kun Zhou and Hui Wang et al. "S^3-Rec: Self-Supervised Learning
    for Sequential Recommendation with Mutual Information Maximization"
    In CIKM 2020.

Reference code:
    https://github.com/RUCAIBox/CIKM2020-S3Rec

"""

import random

import torch
from torch import nn

from recbole.model.abstract_recommender import SequentialRecommender
from recbole.model.layers import TransformerEncoder
from recbole.model.loss import BPRLoss


[docs]class S3Rec(SequentialRecommender): r""" S3Rec is the first work to incorporate self-supervised learning in sequential recommendation. NOTE: Under this framework, we need reconstruct the pretraining data, which would affect the pre-training speed. """ def __init__(self, config, dataset): super(S3Rec, self).__init__(config, dataset) # load parameters info self.n_layers = config['n_layers'] self.n_heads = config['n_heads'] self.hidden_size = config['hidden_size'] # same as embedding_size self.inner_size = config['inner_size'] # the dimensionality in feed-forward layer self.hidden_dropout_prob = config['hidden_dropout_prob'] self.attn_dropout_prob = config['attn_dropout_prob'] self.hidden_act = config['hidden_act'] self.layer_norm_eps = config['layer_norm_eps'] self.FEATURE_FIELD = config['item_attribute'] self.FEATURE_LIST = self.FEATURE_FIELD + config['LIST_SUFFIX'] self.train_stage = config['train_stage'] # pretrain or finetune self.pre_model_path = config['pre_model_path'] # We need this for finetune self.mask_ratio = config['mask_ratio'] self.aap_weight = config['aap_weight'] self.mip_weight = config['mip_weight'] self.map_weight = config['map_weight'] self.sp_weight = config['sp_weight'] self.initializer_range = config['initializer_range'] self.loss_type = config['loss_type'] # load dataset info self.n_items = dataset.item_num + 1 # for mask token self.mask_token = self.n_items - 1 self.n_features = dataset.num(self.FEATURE_FIELD) - 1 # we don't need padding self.item_feat = dataset.get_item_feature() # define layers and loss # modules shared by pre-training stage and fine-tuning stage self.item_embedding = nn.Embedding(self.n_items, self.hidden_size, padding_idx=0) self.position_embedding = nn.Embedding(self.max_seq_length, self.hidden_size) self.feature_embedding = nn.Embedding(self.n_features, self.hidden_size, padding_idx=0) self.trm_encoder = TransformerEncoder( n_layers=self.n_layers, n_heads=self.n_heads, hidden_size=self.hidden_size, inner_size=self.inner_size, hidden_dropout_prob=self.hidden_dropout_prob, attn_dropout_prob=self.attn_dropout_prob, hidden_act=self.hidden_act, layer_norm_eps=self.layer_norm_eps ) self.LayerNorm = nn.LayerNorm(self.hidden_size, eps=self.layer_norm_eps) self.dropout = nn.Dropout(self.hidden_dropout_prob) # modules for pretrain # add unique dense layer for 4 losses respectively self.aap_norm = nn.Linear(self.hidden_size, self.hidden_size) self.mip_norm = nn.Linear(self.hidden_size, self.hidden_size) self.map_norm = nn.Linear(self.hidden_size, self.hidden_size) self.sp_norm = nn.Linear(self.hidden_size, self.hidden_size) self.loss_fct = nn.BCELoss(reduction='none') # modules for finetune if self.loss_type == 'BPR' and self.train_stage == 'finetune': self.loss_fct = BPRLoss() elif self.loss_type == 'CE' and self.train_stage == 'finetune': self.loss_fct = nn.CrossEntropyLoss() elif self.train_stage == 'finetune': raise NotImplementedError("Make sure 'loss_type' in ['BPR', 'CE']!") # parameters initialization assert self.train_stage in ['pretrain', 'finetune'] if self.train_stage == 'pretrain': self.apply(self._init_weights) else: # load pretrained model for finetune pretrained = torch.load(self.pre_model_path) self.logger.info(f'Load pretrained model from {self.pre_model_path}') self.load_state_dict(pretrained['state_dict']) def _init_weights(self, module): """ Initialize the weights """ if isinstance(module, (nn.Linear, nn.Embedding)): # Slightly different from the TF version which uses truncated_normal for initialization # cf https://github.com/pytorch/pytorch/pull/5617 module.weight.data.normal_(mean=0.0, std=self.initializer_range) elif isinstance(module, nn.LayerNorm): module.bias.data.zero_() module.weight.data.fill_(1.0) if isinstance(module, nn.Linear) and module.bias is not None: module.bias.data.zero_() def _associated_attribute_prediction(self, sequence_output, feature_embedding): sequence_output = self.aap_norm(sequence_output) # [B L H] sequence_output = sequence_output.view([-1, sequence_output.size(-1), 1]) # [B*L H 1] # [feature_num H] [B*L H 1] -> [B*L feature_num 1] score = torch.matmul(feature_embedding, sequence_output) return torch.sigmoid(score.squeeze(-1)) # [B*L feature_num] def _masked_item_prediction(self, sequence_output, target_item_emb): sequence_output = self.mip_norm(sequence_output.view([-1, sequence_output.size(-1)])) # [B*L H] target_item_emb = target_item_emb.view([-1, sequence_output.size(-1)]) # [B*L H] score = torch.mul(sequence_output, target_item_emb) # [B*L H] return torch.sigmoid(torch.sum(score, -1)) # [B*L] def _masked_attribute_prediction(self, sequence_output, feature_embedding): sequence_output = self.map_norm(sequence_output) # [B L H] sequence_output = sequence_output.view([-1, sequence_output.size(-1), 1]) # [B*L H 1] # [feature_num H] [B*L H 1] -> [B*L feature_num 1] score = torch.matmul(feature_embedding, sequence_output) return torch.sigmoid(score.squeeze(-1)) # [B*L feature_num] def _segment_prediction(self, context, segment_emb): context = self.sp_norm(context) score = torch.mul(context, segment_emb) # [B H] return torch.sigmoid(torch.sum(score, dim=-1)) # [B]
[docs] def forward(self, item_seq, bidirectional=True): position_ids = torch.arange(item_seq.size(1), dtype=torch.long, device=item_seq.device) position_ids = position_ids.unsqueeze(0).expand_as(item_seq) position_embedding = self.position_embedding(position_ids) item_emb = self.item_embedding(item_seq) input_emb = item_emb + position_embedding input_emb = self.LayerNorm(input_emb) input_emb = self.dropout(input_emb) attention_mask = self.get_attention_mask(item_seq, bidirectional=bidirectional) trm_output = self.trm_encoder(input_emb, attention_mask, output_all_encoded_layers=True) seq_output = trm_output[-1] # [B L H] return seq_output
[docs] def pretrain( self, features, masked_item_sequence, pos_items, neg_items, masked_segment_sequence, pos_segment, neg_segment ): """Pretrain out model using four pre-training tasks: 1. Associated Attribute Prediction 2. Masked Item Prediction 3. Masked Attribute Prediction 4. Segment Prediction """ # Encode masked sequence sequence_output = self.forward(masked_item_sequence) feature_embedding = self.feature_embedding.weight # AAP aap_score = self._associated_attribute_prediction(sequence_output, feature_embedding) aap_loss = self.loss_fct(aap_score, features.view(-1, self.n_features).float()) # only compute loss at non-masked position aap_mask = (masked_item_sequence != self.mask_token).float() * \ (masked_item_sequence != 0).float() aap_loss = torch.sum(aap_loss * aap_mask.flatten().unsqueeze(-1)) # MIP pos_item_embs = self.item_embedding(pos_items) neg_item_embs = self.item_embedding(neg_items) pos_score = self._masked_item_prediction(sequence_output, pos_item_embs) neg_score = self._masked_item_prediction(sequence_output, neg_item_embs) mip_distance = torch.sigmoid(pos_score - neg_score) mip_loss = self.loss_fct(mip_distance, torch.ones_like(mip_distance, dtype=torch.float32)) mip_mask = (masked_item_sequence == self.mask_token).float() mip_loss = torch.sum(mip_loss * mip_mask.flatten()) # MAP map_score = self._masked_attribute_prediction(sequence_output, feature_embedding) map_loss = self.loss_fct(map_score, features.view(-1, self.n_features).float()) map_mask = (masked_item_sequence == self.mask_token).float() map_loss = torch.sum(map_loss * map_mask.flatten().unsqueeze(-1)) # SP # segment context # take the last position hidden as the context segment_context = self.forward(masked_segment_sequence)[:, -1, :] # [B H] pos_segment_emb = self.forward(pos_segment)[:, -1, :] neg_segment_emb = self.forward(neg_segment)[:, -1, :] # [B H] pos_segment_score = self._segment_prediction(segment_context, pos_segment_emb) neg_segment_score = self._segment_prediction(segment_context, neg_segment_emb) sp_distance = torch.sigmoid(pos_segment_score - neg_segment_score) sp_loss = torch.sum(self.loss_fct(sp_distance, torch.ones_like(sp_distance, dtype=torch.float32))) pretrain_loss = self.aap_weight * aap_loss \ + self.mip_weight * mip_loss \ + self.map_weight * map_loss \ + self.sp_weight * sp_loss return pretrain_loss
def _neg_sample(self, item_set): # [ , ] item = random.randint(1, self.n_items - 1) while item in item_set: item = random.randint(1, self.n_items - 1) return item def _padding_zero_at_left(self, sequence): # had truncated according to the max_length pad_len = self.max_seq_length - len(sequence) sequence = [0] * pad_len + sequence return sequence
[docs] def reconstruct_pretrain_data(self, item_seq, item_seq_len): """Generate pre-training data for the pre-training stage.""" device = item_seq.device batch_size = item_seq.size(0) # We don't need padding for features item_feature_seq = self.item_feat[self.FEATURE_FIELD][item_seq] - 1 end_index = item_seq_len.cpu().numpy().tolist() item_seq = item_seq.cpu().numpy().tolist() item_feature_seq = item_feature_seq.cpu().numpy().tolist() # we will padding zeros at the left side # these will be train_instances, after will be reshaped to batch sequence_instances = [] associated_features = [] # For Associated Attribute Prediction and Masked Attribute Prediction long_sequence = [] for i, end_i in enumerate(end_index): sequence_instances.append(item_seq[i][:end_i]) long_sequence.extend(item_seq[i][:end_i]) # padding feature at the left side associated_features.extend([[0] * self.n_features] * (self.max_seq_length - end_i)) for indexes in item_feature_seq[i][:end_i]: features = [0] * self.n_features try: # multi class for index in indexes: if index >= 0: features[index] = 1 except: # single class features[indexes] = 1 associated_features.append(features) # Masked Item Prediction and Masked Attribute Prediction # [B * Len] masked_item_sequence = [] pos_items = [] neg_items = [] for instance in sequence_instances: masked_sequence = instance.copy() pos_item = instance.copy() neg_item = instance.copy() for index_id, item in enumerate(instance): prob = random.random() if prob < self.mask_ratio: masked_sequence[index_id] = self.mask_token neg_item[index_id] = self._neg_sample(instance) masked_item_sequence.append(self._padding_zero_at_left(masked_sequence)) pos_items.append(self._padding_zero_at_left(pos_item)) neg_items.append(self._padding_zero_at_left(neg_item)) # Segment Prediction masked_segment_list = [] pos_segment_list = [] neg_segment_list = [] for instance in sequence_instances: if len(instance) < 2: masked_segment = instance.copy() pos_segment = instance.copy() neg_segment = instance.copy() else: sample_length = random.randint(1, len(instance) // 2) start_id = random.randint(0, len(instance) - sample_length) neg_start_id = random.randint(0, len(long_sequence) - sample_length) pos_segment = instance[start_id:start_id + sample_length] neg_segment = long_sequence[neg_start_id:neg_start_id + sample_length] masked_segment = instance[:start_id] + [self.mask_token] * sample_length \ + instance[start_id + sample_length:] pos_segment = [self.mask_token] * start_id + pos_segment + \ [self.mask_token] * (len(instance) - (start_id + sample_length)) neg_segment = [self.mask_token] * start_id + neg_segment + \ [self.mask_token] * (len(instance) - (start_id + sample_length)) masked_segment_list.append(self._padding_zero_at_left(masked_segment)) pos_segment_list.append(self._padding_zero_at_left(pos_segment)) neg_segment_list.append(self._padding_zero_at_left(neg_segment)) associated_features = torch.tensor(associated_features, dtype=torch.long, device=device) associated_features = associated_features.view(-1, self.max_seq_length, self.n_features) masked_item_sequence = torch.tensor(masked_item_sequence, dtype=torch.long, device=device).view(batch_size, -1) pos_items = torch.tensor(pos_items, dtype=torch.long, device=device).view(batch_size, -1) neg_items = torch.tensor(neg_items, dtype=torch.long, device=device).view(batch_size, -1) masked_segment_list = torch.tensor(masked_segment_list, dtype=torch.long, device=device).view(batch_size, -1) pos_segment_list = torch.tensor(pos_segment_list, dtype=torch.long, device=device).view(batch_size, -1) neg_segment_list = torch.tensor(neg_segment_list, dtype=torch.long, device=device).view(batch_size, -1) return associated_features, masked_item_sequence, pos_items, neg_items, \ masked_segment_list, pos_segment_list, neg_segment_list
[docs] def calculate_loss(self, interaction): item_seq = interaction[self.ITEM_SEQ] item_seq_len = interaction[self.ITEM_SEQ_LEN] # pretrain if self.train_stage == 'pretrain': features, masked_item_sequence, pos_items, neg_items, \ masked_segment_sequence, pos_segment, neg_segment \ = self.reconstruct_pretrain_data(item_seq, item_seq_len) loss = self.pretrain( features, masked_item_sequence, pos_items, neg_items, masked_segment_sequence, pos_segment, neg_segment ) # finetune else: pos_items = interaction[self.POS_ITEM_ID] # we use uni-directional attention in the fine-tuning stage seq_output = self.forward(item_seq, bidirectional=False) seq_output = self.gather_indexes(seq_output, item_seq_len - 1) 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) return loss
[docs] def predict(self, interaction): item_seq = interaction[self.ITEM_SEQ] item_seq_len = interaction[self.ITEM_SEQ_LEN] test_item = interaction[self.ITEM_ID] seq_output = self.forward(item_seq, bidirectional=False) seq_output = self.gather_indexes(seq_output, item_seq_len - 1) 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] item_seq_len = interaction[self.ITEM_SEQ_LEN] seq_output = self.forward(item_seq, bidirectional=False) seq_output = self.gather_indexes(seq_output, item_seq_len - 1) test_items_emb = self.item_embedding.weight[:self.n_items - 1] # delete masked token scores = torch.matmul(seq_output, test_items_emb.transpose(0, 1)) # [B, n_items] return scores