[ROCm][DSV4] Use aiter mHC pre/post as the default ROCm path

[Fangzhou-Ai]

Purpose

Re-enable the aiter multi-head-consensus (mHC) pre/post ops as the preferred ROCm path for DeepSeek V4. #43679 introduced the tilelang fused post+pre mHC kernel and explicitly left a hook to switch back to the (faster) aiter mHC kernels once an aiter release containing the mhc_pre_gemm_sqrsum_kernel race-condition fix was available. This is that follow-up.

Dispatch / fallback path

Selection is purely capability based — no new env knobs:

aiter mHC pre/post  ->  tilelang fused post+pre  ->  torch/triton reference

• aiter mHC pre/post (preferred): used whenever aiter is available on a supported ROCm device (is_aiter_found_and_supported(), i.e. ROCm + gfx9/MI3xx + aiter installed) and the hidden size is a multiple of 256 (kernel constraint).
• tilelang fused post+pre (fallback): used on CUDA always, and on ROCm when aiter is unavailable / the hidden-size constraint is not met.
• torch/triton reference (final fallback): used when tilelang is also unavailable.

The unfused aiter path applies hc_post inline and returns no residual streams, so the deferred hc_post in DeepseekV4Model.forward and the MTP layer is gated on residual is not None rather than has_tilelang/is_cuda.

The aiter mHC kernels require aiter >= 0.1.14, which contains the sqrsum race-condition fix in mhc_pre_gemm_sqrsum_kernel (ROCm/aiter@b639cb6); without it results are wrong at large token counts. AITER_BRANCH in docker/Dockerfile.rocm_base is bumped v0.1.13 -> v0.1.14.

Not a duplicate

This is the aiter follow-up that #43679 (merged) explicitly deferred. A scan of open PRs (mHC, deepseek v4 mhc aiter) shows the other ROCm DSv4 PRs cover unrelated areas (#42893 MI300X functional fixes, #41136 model enablement, #41451 MI300 support, #40909/#40892 AITER MLA decode, #42735 tilelang mHC-pre perf). None re-enables the aiter mHC pre/post path. No overlap.

Test Plan

ROCm, 8x MI3xx, DeepSeek-V4-Pro, tp=8, --kv-cache-dtype fp8, --moe-backend triton_unfused, --compilation-config '{"mode":3,"cudagraph_mode":"FULL_AND_PIECEWISE"}'.

• Accuracy: gsm8k via lm_eval (--num_fewshot 20) on the aiter mHC path.
• Performance: vllm bench serve (random, --random-range-ratio 0.8, --num-warmups C*2, --num-prompts C*5) comparing aiter mHC vs the tilelang fused kernel at 1k/1k and 8k/1k, concurrency 4 and 64.

Test Result

Accuracy — gsm8k (num_fewshot=20, aiter mHC, no MTP)

Filter	Metric	Value	Stderr
flexible-extract	exact_match	0.9507	±0.0060
strict-match	exact_match	0.9515	±0.0059

Within #43679's accuracy gate (0.95 ± 0.01; tilelang baseline there: 0.9553 / 0.9560). A 20-shot run was used specifically to stress large token counts and confirm the aiter v0.1.14 sqrsum fix (v0.1.13 regressed badly under that stress).

Performance — aiter mHC vs tilelang fused (output tok/s, higher is better)

1k/1k (input 1024 / output 1024):

Concurrency	tilelang	aiter	Output gain	tilelang TPOT (ms)	aiter TPOT (ms)
4	85.45	91.22	+6.8%	42.35	39.76
64	760.36	796.07	+4.7%	73.30	70.10

8k/1k (input 8192 / output 1024):

Concurrency	tilelang	aiter	Output gain	tilelang TPOT (ms)	aiter TPOT (ms)
4	74.83	79.55	+6.3%	47.69	44.72
64	521.70	559.19	+7.2%	108.05	101.03

aiter mHC is consistently faster than the tilelang fused kernel across both workloads and concurrencies (+4.7% to +7.2% throughput, lower TPOT). The tilelang baseline matched #43679's published numbers.

Path verification: with aiter present, workers log [aiter] import [module_mhc] .../module_mhc.so and generation is correct; forcing the fallbacks (no aiter / no tilelang) exercises the tilelang and torch/triton paths.

pre-commit run --files (ruff, ruff-format, mypy, typos, SPDX, ...) passes on all changed files.

---

AI assistance (Cursor) was used to prepare this change; the human submitter has reviewed every changed line and run the tests above.

Made with Cursor

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[mergify]

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[AndreasKaratzas]

There is release cadence for ROCm major lib version bumps.

cc @micah-wil @Rohan138 @dllehr-amd

[tjtanaa]

@Fangzhou-Ai on upstream we do not bump other dependencies version. So this PR will only be continued after aiter is upgraded.