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[Engine] strata-sycl.sh drops every STRATA_* variable whose value is 0, so the documented STRATA_PREFILL_MMQ=0 (FP16 prompt path) never reaches the engine; "off" works by accident

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Valutazione

Difficoltà
2/5
Tempo stimato
1-3 ore
Idoneità per principianti
74/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
bash, cpp, docker
Ambito
backend, cli

Direzione di ricerca

Inizia dal ciclo di inoltro dell’ambiente in sycl/serve/strata-sycl.sh e segui come viene creato l’array setting a partire dall’ambiente di configurazione. Riproduci il caso con STRATA_PREFILL_MMQ=0 bash -x sycl/serve/strata-sycl.sh --version e controlla gli argomenti di docker run; confronta con =off. Il lavoro è concluso quando il valore documentato 0 raggiunge il motore come STRATA_PREFILL_MMQ=0 e il comportamento degli altri switch del launcher è chiaro.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Area

[Engine] (the SYCL serve path: sycl/serve/strata-sycl.sh, the config's exe on Intel)

Desktop app, Terminal or source?

Source

What happened

The launcher forwards STRATA_* (and ONEAPI_/UR_/IGC_/SYCL_/ZES_) variables into the container, but skips every one whose value is 0 or empty:

for k in "${!setting[@]}"; do
    # the engine tests the switches by presence: a value of 0 (or empty) means "not set", so it is not passed on
    case "${setting[$k]}" in 0|"") ;; *) envs+=(-e "$k=${setting[$k]}") ;; esac
done

That is right for a switch whose unset default is off, and wrong for a three-state switch where unset means "auto". STRATA_PREFILL_MMQ is one: unset = auto on Battlemage, 0 = the FP16 path. 0 is the documented value (docs/INTEL_INT8_EXPERTS.md: "STRATA_PREFILL_MMQ=0: the FP16 path everywhere"; the 0.2.0 release notes), and it is what the engine itself prints at start: int8 prompt experts are on (Battlemage default, auto); STRATA_PREFILL_MMQ=0 turns them off. A config with "env": {"STRATA_PREFILL_MMQ": "0"} (the documented way to give the engine a setting: the server puts the env block into the launcher's environment) starts the auto path anyway, and the log advises the value that was just dropped.

Trace, bash -x sycl/serve/strata-sycl.sh --version:

  • with STRATA_PREFILL_MMQ=0 the exec docker run line carries only the launcher's three defaults: -e STRATA_VERIFY_NO_HOST=1 -e STRATA_VERIFY_DEVICE_PLAN=1 -e STRATA_STAGER_THREADS=12;
  • with STRATA_PREFILL_MMQ=off it also carries -e STRATA_PREFILL_MMQ=off. "off" works only because choose_mode() in sycl/include/strata/prefill/esimd_moe.hpp parses a non-digit string as 0, which no document says.

Seen with the real engine (2026-10-26, v0.2.6 build): an A/B arm whose config env had STRATA_PREFILL_MMQ=0 logged int8 prompt experts are on (Battlemage default, auto) and ran at the auto path's speed (1115 tok/s on a 6,345-token prompt, against 1316 with "off"; the numbers are in the int8 issue I am filing next).

The launcher's own header example, "env": {"STRATA_VERIFY_NO_HOST": "0"}, works by accident: the 0 replaces the launcher's default 1 in the setting array and is then dropped, and the engine's unset default happens to be the same as 0. Other =0 forms the Intel docs give and the launcher cannot deliver: STRATA_I8_FORCE=0, STRATA_I8_WG=0, STRATA_MMVQ_A2=0, STRATA_MMVQ_WIDE_32=0, STRATA_LEND_MIRROR=0, STRATA_ARENA_ALIAS_CHECK=0, STRATA_SPLIT_HEADROOM=0, STRATA_MIRROR_MIB=0 (docs/INTEL.md, INTEL_ARC.md, INTEL_INT8_EXPERTS.md). I did not check which of those have an unset default equal to 0 and which do not.

Expected: a value the config's env block names reaches the engine as written. If some engine switches really are presence-tested (so that K=0 would turn them on), a short list of those names to keep dropping, or a list of the three-state names to pass through, would avoid this; dropping every 0 silently is what bites.

Smallest steps or command that reproduce it
  1. Intel install per docs/INTEL_ARC.md.
  2. In the run config: "env": {"STRATA_PREFILL_MMQ": "0"}; start the server; the engine log says int8 prompt experts are on (Battlemage default, auto).
  3. Change the value to "off": no int8 lines, FP16 timings.
  4. Without a GPU: STRATA_PREFILL_MMQ=0 bash -x sycl/serve/strata-sycl.sh --version 2>&1 | grep 'exec docker run' has no -e STRATA_PREFILL_MMQ; with =off it has.
Reproduction status

Reproduced locally

Strata version

Source v0.2.7.1 (46c152a1), engine 0.1.53 built from it; strata-sycl.sh is identical on main today and was the same on v0.2.6.

Graphics card, memory and system

Intel Arc Pro B70 32 GB · 62 GB RAM · Debian 13 (kernel 7.2.6, xe driver); engine in the strata-sycl-dev container

Model, size and settings

Qwen3.8-Flash-Next IQ3_S (native pack, --stream-experts, --prefill 4096), 256K context, pictures off

Logs

The trace lines above, and the engine's int8 prompt experts are on (Battlemage default, auto); STRATA_PREFILL_MMQ=0 turns them off under a config env of 0.

Lingua principale
C++
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