Graph Neural Network (GNN) is the trending solution for item retrieval in recommendation problems. Most recent reports, however, focus heavily on new model architectures. This may bring some gaps when applying GNN in the industrial setup, where, besides the model, constructing the graph and handling data sparsity also play critical roles in the overall success of the project. In this work, we report how GNN is applied for large-scale e-commerce item retrieval at Shopee. We introduce our simple yet novel and impactful techniques in graph construction, modeling, and handling data skewness. Specifically, we construct high-quality item graphs by combining strong-signal user behaviors with high-precision collaborative filtering (CF) algorithm. We then develop a new GNN architecture named LightSAGE to produce high-quality items' embeddings for vector search. Finally, we design multiple strategies to handle cold-start and long-tail items, which are critical in an advertisement (ads) system. Our models bring improvement in offline evaluations, online A/B tests, and are deployed to the main traffic of Shopee's Recommendation Advertisement system.

In this paper, we introduce the group concept into multi-agent reinforcement learning. In this method, agents are divided into several groups and each group completes a specific subtask so that agents can cooperate to complete the main task. Existing methods use the communication vector to exchange information between agents. This may encounter communication redundancy. To solve this problem, we propose a MARL method based on graph clustering. It allows agents to adaptively learn group features and replaces the communication operation. In our method, agent features are divide into two types, including in-group features and individual features. They represent the generality and differences between agents, respectively. Based on the graph attention network(GAT), we introduce the graph clustering method as a punishment to optimize agent group feature. Then these features are used to generate individual Q value. To overcome the consistent problem brought by GAT, we introduce the split loss to distinguish agent features. Our method is easy to convert into the CTDE framework via using Kullback-Leibler divergence method. Empirical results are evaluated on a challenging set of StarCraft II micromanagement tasks. The result shows that our method outperforms existing multi-agent reinforcement learning methods and the performance increases with the number of agents increasing.