Exact for all 256 e4m3fn codes and RNE encode on host; tiny golden 9/9.
vllm-sonnet 512: TPOT 228.6 -> 223.3 ms, TTFT 4349 -> 4117 ms, tokens/step unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
- The state buffer's column regions get their own allocations on Neuron:
a layer's uint8 SWA cache and fp32 compressor state are both region graph
inputs, and aot_autograd compares offsets of differently typed views of one
storage in their own element units (false overlap -> 'input mutations on
views with different dtypes').
- paged_mqa_logits chunk path: gather the keys the chunk's last token sees
(lens.max()), not the first token's.
- Debug: DEEPINFER_NEURON_ALIAS_DEBUG prints aliased graph inputs; a cProfile
of decode step 8 under DEEPINFER_NEURON_REGION_TIMING.
Tiny V4.1 on a NeuronCore, bucket 128: short 8/9 (= eager), long 715 tokens
in 6 chunks 9/9 (eager 8/9) in 26 s instead of 978 s of eager prefill.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Fixes found by reducing neuronx-cc NCC_IINL902 crashes to minimal reproducers (crash rates over repeated
compiles, the compiler is nondeterministic on these graphs):
- uint8 byte assembly of narrowed values (KV records, e2m1/e4m3 codes, ue8m0 exponents) crashed or
silently corrupted bytes: producers keep int32 codes under compile and stores narrow once
(fused_transform, kv_quant, store_kv_cache; neuron_compile.encode_codes).
- int16 packed scales written through a uint8 view and read back in the same graph: the Neuron kernel
now receives the int16 storage and packs byte pairs arithmetically (_alloc_quant, return_quant).
- fp8 legalization pass treated plain float->bf16 conversions as fp8 carriers (wrong values + crash).
- Projection stage split further (nullcontext instead of a disabled CP session).
Device (tiny model, regions mode): every decode graph compiles; argmax vs golden short 9/9,
medium 8/9 (step 6 near-tie, margin 0.065), long 9/9, cos 0.997-0.9995.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
- Decode runs eagerly and compiles per-layer regions (attention half, MoE) with stage boundaries
(neuron_ops/regions.py, DEEPINFER_NEURON_GRAPH_MODE=regions); layer KV views are sliced from the
roots inside the graph (_LazyKVCache).
- vllm-neuron#71 NKI kernels (Apache-2.0, vendored under neuron_ops/nki/ with attribution), called via
torch_neuronx.nki_hop.wrap_nki: blockquant (fp8/fp4 GEMMs incl. grouped einsum, MoE and shared
expert on bf16 activations), sparse_attn / index_score / compress_pool (nki_attention.py),
hc_mixes / hc_expand / hc_collapse / hc_attn_out / rmsnorm / swiglu (nki_hc.py, nki_norm.py).
- Compile-safe formulations: row-major scales, no dtype bitcasts of graph inputs (uint8 weight
tensors), whole-row KV stores, byte assembly in int32 narrowed once at the store, arithmetic int16
scale packing, plain fma/rsqrt and bf16 F.linear under compile; default backend deepinfer_neuron
(torch fp8 carried as uint8, avoiding NCC_EOCP001 with the kernels' OCP fp8).
- Host: tiny model 9/9 vs golden on all prompts; device: kernel tests pass (13 attention, 88 hc/norm);
region decode graph compiles except the attention projection stage (being reduced).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
- NeuronGraphRunner: the CudaGraphRunner contract over torch.compile(dynamic=False), one graph per
batch size (DEEPINFER_ENFORCE_EAGER=0, backend DEEPINFER_NEURON_COMPILE_BACKEND). Layer cache views are
re-sliced from their root allocations inside the graph, so AOT never regenerates aliased mutated
inputs with as_strided.
- Decode MoE with fixed shapes: packed all-gather, dense local experts, fp32 reduce-scatter
(neuron_ops/static_moe.py, deep_gemm.m_grouped_fp8_fp4_gemm_nt_shared_a).
- Graph-break and compile fixes: hide torch.cuda during compile, torch.device equality for FX codegen,
hash-based force_random routing, Engram hash/fetch on the host (exact int64), env vars resolved before
tracing, Movable annotation, no .item()/nonzero/as_strided writes on the decode path, KV stores route
padding slots to a scratch block kept past the pool, native-dtype gather under compile.
- fp8: trn2 reads float8_e4m3fn as IEEE e4m3 (max 240). Activations/KV quantize to 224
(DEEPINFER_NEURON_FP8_MAX), checkpoint fp8 weights are rescaled at load (bytes / 2, ue8m0 + 1), and
neuronx-cc gets --experimental-unsafe-fp8e4m3fn-as-fp8e4m3 via --internal-hlo2tensorizer-options.
The uint8-carrier backend (neuron_ops/neuron_compile.py, "deepinfer_neuron") stays as a fallback.
- Tests: tests/neuron/compile; run_all.sh runs kernel unit tests at the e4m3fn range (448) and the
end-to-end stages at 224. Docs: vllm-neuron PR #71 analysis and compile notes.
Host: tiny model 9/9 vs golden (all prompts) eager, compiled path (aot_eager) matches eager; CPU suite green.
Device: the whole decode graph still crashes neuronx-cc (NCC_IINL902, being bisected).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
