Agent skill · NVIDIA
nemo-mbridge-perf-moe-long-context
Long-context MoE training guidance for Megatron Bridge. Covers CP sizing, selective recompute, dispatcher choices, and practical patterns from DSV3, Qwen3, and Qwen3-Next long-context experiments.
What it needs
About 3k tokens when loaded.
What this skill does
MoE Long-Context Training Stable docs: @docs/training/moe-optimization.md Card: @skills/nemo-mbridge-perf-moe-long-context/card.yaml What Changes At Long Context Once sequence length moves well past the 4K-class regime, attention memory and activation residency become the dominant constraints. For MoE models, that usually means you need some combination of: context parallelism selective recompute lower precision CPU offload for optimizer state a dispatcher and PP layout that do not waste the smaller remaining DP budget Rounded Scaling Patterns DSV3 on H100 The DSV3 long-context runs show a stable pattern: selective recompute works better than full recompute once you move past the shortest contexts throughput stays in a fairly narrow band from mid-length through very long contexts if CP is increased appropriately the trade shifts from "memory fit" to "GPU-count feasibility" as CP grows In other words, long context does not immediately collapse utilization if the layout is chosen well, but it does consume the DP budget very quickly. Qwen3-Next on GB200 Qwen3-Next behaves more like a memory-sensitive medium-scale model: 8K and 32K remain practical with moderate CP 64K is possible, but the throughput drop is noticeable and memory becomes much tighter pipeline layout and grouped-GEMM improvements matter almost as much as CP Qwen3 235B on GB200 Qwen3 235B shows that long context can still be efficient on NVL72 systems when TP, CP, and HybridEP are coordinated. The best 128K-class configurations are not just "fit-only" recipes; they can remain highly efficient if routing, parallelism, and recompute are balanced. CP Sizing Rules Of Thumb 1. Start from a 4K shard target: a good first guess is CP ~= seqlen / 4096, then round to a practical power-of-two layout. 2. Keep DP alive if possible: long-context scaling becomes brittle once CP, EP, TP, and PP together squeeze DP down to the floor. 3. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills NVIDIA/nemo-mbridge-perf-moe-long-context