The pure-torch sparse attention followed FlashMLA's tests/ref.py (fp32 P).
The CUDA kernels (sm100 prefill phase1.cuh:238-253) and the official
reference round P = exp(s - running_max) to bf16 before the P@V GEMM in an
online softmax; do the same with 64-key blocks.
Localized with examples/neuron/probe_layer0.py (per-op reference vs DeepInfer
capture): layer 0 is now bit-exact up to two rounding points that are
DeepInfer's own GPU/Ascend behaviour (SwiGLU -> FP8 from fp32, bf16 routed
partial in the MoE combine). CPU end-to-end on the tiny checkpoint: 26/27
greedy tokens match the reference, the miss being a 0.0096-margin step the
reference flips against itself.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
