# EXP-SIMFID-Q30-FIXED-PRESSURE-SURFACE: high-pressure Fixed-PD / Fixed-PO

> Status: approved and launching (2026-07-19).

## Question

When uniform Fixed-PD is moved from the near-singleton workload to
`4096 -> 256` at `1.125` request/s/GPU, does Frontier still choose a different
latency-optimal configuration from real community vLLM 0.20? Does removing
decode (`4096 -> 1`) change that selection boundary?

## Setup and decision rule

- Qwen3-30B-A3B BF16 on dash0 H20; community vLLM 0.20.0.
- Fixed-PD `4096 -> 256` and Fixed-PO `4096 -> 1`; 257 uniform,
  prefix-disjoint requests; prefix caching off.
- Rate is frozen at 1.125 request/s/GPU, so global rates are 1.125, 2.25, and
  4.5 request/s for TP1, TP2, and TP4.
- Surface: `TP in {1,2,4}` x `MNS in {8,16,32,64}`, MBT=8192. Real
  measurements use three fresh-server trials with rotated order.
- Frontier is `deadc4a`, `piecewise`, the frozen CUDA-event profile plus the
  graph-compatible KERNEL_ONLY profile and measured collectives used by the
  prior Trace-PD comparison. No latency calibration is fitted to this case.
- Compare exact winners, selected-config real regret, and pairwise order for
  mean/p90 TTFT, E2E, and TPOT where decode exists. SLO is not scored.

The pressure-probe measurements selected the workload but are excluded from
the real evaluation pool. A failed or incomplete Frontier cell is a coverage
failure, not a high-latency observation.

## Expected output and decision

The final table has one row per case/objective with Frontier winner, real
winner, regret, and pairwise agreement. If the old Fixed-PD reversal persists,
the failure is not an artifact of singleton load. If it disappears, simulator
fidelity has a load-regime boundary that must be localized. Fixed-PO isolates
whether decode-state composition is necessary for either outcome.

The previously reviewed matrix schematic remains the figure prototype:
`../simulator-tuning-latency-matrix-v0/latency-selection-matrix-schematic.svg`.

## Provenance

Remote output root:
`dash0:/home/admin/cpfs/wjh/aituner/qwen30-fixed-pressure-surface-20260719-r1`.
The campaign records source/profile/model hashes, runtime versions, GPU
inventory, per-cell commands, raw request records, and an artifact checksum
manifest.