# NVFP4 Mega MoE Kernel — Mojo Rewrite

Rewrite of the DeepGEMM `fp8_nvfp4_mega_moe` kernel in Mojo.

## Why Mojo?
- Python-like syntax, C-level performance
- Direct GPU programming without PTX inline asm
- Safer than CUDA C++ (ownership, borrowing)
- Better ergonomics for complex kernel development

## Architecture

The kernel performs NVFP4 (E2M1 + UE4M3 block16 scales) matrix multiply
for MoE (Mixture of Experts) with expert parallelism across NVLink.

### Key operations:
1. **Staging** — quantize BF16 activation to FP4 (E2M1) with UE8M0 scales
2. **TMA load** — load packed FP4 weights and UE4M3 scales from global memory
3. **UMMA** — `mxf4nvf4` matrix multiply with block scaling
4. **Epilogue** — quantize L1 output (BF16 → FP4 + UE4M3 scales for L2)
5. **NVLink sync** — cross-rank barrier and buffer management

### NVFP4 specifics (vs MXFP4):
- group_size=16 (UE4M3 block scales), not group_size=32 (UE8M0)
- 2 SF K-columns per BLOCK_K (128/16/4=2), not 1
- Weights are E2M1 packed int8 (2 values per byte)
- `mxf4nvf4` UMMA instruction with `scale_vec::4X`

## Structure
```
src/
  mega_moe.mojo    — main kernel entry point
  staging.mojo     — activation quantization (BF16 → FP4)
  tma.mojo         — TMA descriptor creation and copy
  umma.mojo        — UMMA descriptor and MMA operations
  epilogue.mojo    — output quantization and TMA store
  barrier.mojo     — NVLink cluster sync and symm buffer
  layout.mojo      — weight transformation and SF layout
  utils.mojo       — math helpers, UE4M3 packing
```