UniEP: Unified Expert-Parallel MegaKernel MoE for LLM Training

As LLM training grows increasingly resource-intensive and expert parallelism (EP) becomes essential for scaling MoE models, EP optimizations are widely adopted in production frameworks like Megatron-LM. Existing solutions often rely on ad-hoc, complex kernels that lack adaptability across diverse optimization configurations and frequently neglect numerical stability, failing to meet the strict precision requirements of large-scale training.