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aituner/runs/frontier-split-rootcause-v0/frozen-inputs/q235-state-diag/state-diagnosis-exact.md
2026-07-20 12:05:20 +08:00

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Qwen235 Fixed-PD state diagnosis

Verdict: Exact real state composition flips Frontier to the correct TP4 winner; the ranking error is caused by closed-loop state/composition mismatch, not a conditional stage reversal.

Config Real Running proxy mean Sim decode batch mean Proxy coverage
tp4_ep1_mns64 4.667 13.537 100.0%
tp8_ep8_mns64 12.238 18.938 100.0%
Config Real exact decode batch mean Real token-weighted iteration ms Matched simulator ms Exact coverage
tp4_ep1_mns64 3.890 18.4710 34.2575 100.0%
tp8_ep8_mns64 10.921 27.5887 45.1603 100.0%

Frontier internal component contrast over its own executed composition

Decode-token-weighted over both pure-decode and mixed prefill/decode steps.

Component TP8 - TP4 (ms/decoded token step)
moe_compute -32.4544
total -20.0663
attention -7.4619
tp_dp_communication -6.5711
ep_communication +6.2354
moe_routing -0.2862
dense_mlp_compute -0.1231
pipeline_communication +0.0000
runtime_overhead +0.0000

Frontier component contrast at exact real token composition

Positive means TP8 slower; negative means Frontier gives TP8 an advantage.

Component TP8 - TP4 (ms/step)
total +10.9028
ep_communication +6.5355
tp_dp_communication -6.4718
attention -2.1304
moe_compute -1.9774
moe_routing +0.1384
dense_mlp_compute -0.0308
pipeline_communication +0.0000
runtime_overhead +0.0000

Interpretation boundary

  • Real observed TPOT contrast: +6.9500 ms/token.
  • Real exact-iteration contrast: +9.1177 ms/decode-token-weighted step.
  • vLLM 10-second Running is active requests, not per-iteration decode batch; context lengths and graph buckets are unavailable in frozen logs.
  • Frontier state outputs have no direct graph bucket/padding/launch-overhead field; graph effects remain folded into predictors.
  • For TP8 shared-domain sync, total is ledger stage_end-start (critical path); op categories are serialized work estimates and are not additive because overlap and lane-summed wait diagnostics are represented separately.
  • Component deltas identify where Frontier creates its own TP8 advantage; without real per-stage measurements they are not yet root-cause proof.