Zhi Ma

Jinliang Shi, Shigang Li, Youxuan Xu et al.

Sparse matrix multiplication operators (i.e., SpMM and SDDMM) are widely used in deep learning and scientific computing. Modern accelerators are commonly equipped with Tensor cores and CUDA cores to accelerate sparse operators. The former brings superior computing power but only for structured matrix multiplication, while the latter has relatively lower performance but with higher programming flexibility. In this work, we discover that utilizing one resource alone leads to inferior performance for sparse matrix multiplication, due to their respective limitations. To this end, we propose Libra, a systematic approach that enables synergistic computation between CUDA and Tensor cores to achieve the best performance for sparse matrix multiplication. Specifically, we propose a 2D-aware workload distribution strategy to find out the sweet point of task mapping for different sparse operators, leveraging both the high performance of Tensor cores and the low computational redundancy on CUDA cores. In addition, Libra incorporates systematic optimizations for heterogeneous computing, including hybrid load-balancing, finely optimized kernel implementations, and GPU-accelerated preprocessing. Extensive experimental results on H100 and RTX 4090 GPUs show that Libra outperforms the state-of-the-art by on average 3.1x (up to 9.23x) over DTC-SpMM and 2.9x (up to 3.9x) for end-to-end GNN applications. Libra opens up a new perspective for sparse operator acceleration by fully exploiting the heterogeneous computing resources on GPUs.

Xiao Liang, Jiawei Hu, Di Wang et al.

Vision-language models (VLMs) are prone to hallucinations that critically compromise reliability in medical applications. While preference optimization can mitigate these hallucinations through clinical feedback, its implementation faces challenges such as clinically irrelevant training samples, imbalanced data distributions, and prohibitive expert annotation costs. To address these challenges, we introduce CheXPO, a Chest X-ray Preference Optimization strategy that combines confidence-similarity joint mining with counterfactual rationale. Our approach begins by synthesizing a unified, fine-grained multi-task chest X-ray visual instruction dataset across different question types for supervised fine-tuning (SFT). We then identify hard examples through token-level confidence analysis of SFT failures and use similarity-based retrieval to expand hard examples for balancing preference sample distributions, while synthetic counterfactual rationales provide fine-grained clinical preferences, eliminating the need for additional expert input. Experiments show that CheXPO achieves 8.93% relative performance gain using only 5% of SFT samples, reaching state-of-the-art performance across diverse clinical tasks and providing a scalable, interpretable solution for real-world radiology applications.