Prime Flash MoE - Faster MoE Kernels optimized for Blackwell
Blog post from Prime Intellect
Prime Flash MoE is a set of CUDA kernels optimized for NVIDIA Blackwell GPUs that accelerates Mixture-of-Experts feed-forward layers with SwiGLU activations by reducing intermediate memory traffic, reporting up to 2.4× faster performance than PyTorch grouped GEMM and about 2.3× speedup across 4k–128k tokens. Its fused pipeline combines gathering, gate/up projection, SwiGLU, and down projection while keeping activations on-chip, using tensor-map interleaving to place paired gate and up values in the same CTA and treating the down projection as a split-K operation whose partial outputs are accumulated globally. Because split-K reduction traffic grows with problem size, a separate split pipeline materializes the smaller activation tensor once in memory and performs a conventional down-projection GEMM, making it the default for larger workloads. The implementation uses Blackwell-specific features including Tensor Memory Accelerator transfers, hardware swizzling, tensor-memory accumulators, asynchronous barriers, and hardware-assisted reductions that combine expert routing, split-K accumulation, and output scattering. Both bf16 and MXFP8 variants share the overall architecture, while MXFP8 additionally handles block scaling and quantizes intermediate activations on-chip. Benchmarks on NVIDIA B200 GPUs compare the kernels with per-expert PyTorch loops and grouped GEMM baselines under matched routing and quantization conditions.
| Trend | Post Mentions | Total Month Mentions | Posts | Companies | MoM |
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