Shuai Zhang

Yongjun He, Shuai Zhang, Jiading Gai et al. · amazon-science

As large language models (LLMs) continue to scale and new GPUs are released even more frequently, there is an increasing demand for LLM post-training in heterogeneous environments to fully leverage underutilized mid-range or previous-generation GPUs and alleviate the shortage of homogeneous high-end GPUs within a single availability zone. However, achieving high-performance reinforcement learning (RL) training for LLMs on such computing resources remains challenging because the workflow involves multiple models and tasks with complex computation and data dependencies. In this paper, we present HetRL, a distributed system for efficient RL training in infrastructures with heterogeneous GPUs and networks. HetRL formulates the scheduling of RL training in heterogeneous environments as a constrained joint optimization problem and provides two complementary approaches for addressing this problem: (1) a hybrid scheduling algorithm that efficiently identifies near-optimal solutions, and (2) an integer linear programming (ILP)-based scheduling algorithm that obtains optimal solutions, enabling flexible trade-offs between solution optimality and efficiency. Our extensive evaluation, consuming 20,000 GPU-hours, shows that HetRL achieves up to 9.17x the throughput of state-of-the-art systems, and 3.17x on average, across a wide range of workloads and settings.

Jinyang Wu, Mingkuan Feng, Shuai Zhang et al.

Multimodal large language models excel across diverse domains but struggle with complex visual reasoning tasks. Current approaches aim to incorporate structured thinking via two strategies: explicit search methods and post-training techniques. However, both approaches face significant limitations: Search-based methods suffer from computational inefficiency due to extensive solution space exploration, while post-training methods require substantial data, computational resources, and often encounter training instability. To address these limitations, we propose AStar, an \textbf{A}utomated \textbf{S}tructured \textbf{t}hinking paradigm for multimod\textbf{a}l \textbf{r}easoning. Our method introduces "thought cards", a lightweight library of high-level reasoning patterns abstracted from 500 prior samples using Monte Carlo Tree Search. For each test problem, AStar adaptively retrieves the optimal thought cards and seamlessly integrates these external explicit guidelines with the model's internal implicit reasoning capabilities. Extensive experiments demonstrate AStar's effectiveness and efficiency: using only 500 prior samples and a 7B backbone, our training-free framework achieves 53.9$\%$ accuracy on MathVerse (surpassing GPT-4o's 50.2%) and 32.7% on MathVision (versus GPT-4o's 30.4%). Further analysis reveals that AStar generalizes beyond multimodal reasoning to visual perception and understanding domains, and serves as a plug-and-play test-time inference method compatible with mainstream post-training techniques like GRPO.