[TRTLLM-9295][fix] use greedy decoding in test_openai_compatible_json_schema

[ixlmar]

Description

This PR makes the test pass when FlashInfer.sampling is enabled (cf. #9270).

Test Coverage

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Summary by CodeRabbit

Release Notes

This release contains no user-facing changes. Internal test configurations have been updated to support ongoing development and quality assurance efforts.

[ixlmar]

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[coderabbitai]

📝 Walkthrough

Walkthrough

A temperature parameter set to 0.0 was added to a chat.completions.create API call within a test method, modifying the request configuration without altering test logic or public APIs.

Changes

Cohort / File(s)	Change Summary
Test API Configuration tests/unittest/llmapi/apps/_test_openai_chat_guided_decoding.py	Added temperature=0.0 parameter to chat.completions.create call in test_openai_compatible_json_schema test method

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

• Isolated test file modification with single parameter addition
• No logic changes or public API modifications

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding greedy decoding (temperature=0.0) to a test. It is directly related to the changeset and follows the repository template format.
Description check	✅ Passed	The description provides the context (FlashInfer.sampling enablement) and references a related issue, but lacks specific technical details about how the fix works or why temperature=0.0 implements greedy decoding.

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📥 Commits

Reviewing files that changed from the base of the PR and between 46dd988 and 15f1eec.

📒 Files selected for processing (1)

• tests/unittest/llmapi/apps/_test_openai_chat_guided_decoding.py (1 hunks)

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🔇 Additional comments (1)

tests/unittest/llmapi/apps/_test_openai_chat_guided_decoding.py (1)

139-139: Now let me search for context about why the fix is applied only to one test:

Let me search for more specific information about whether both test variants should have the temperature fix:

Based on my verification, I now have a clear picture of why only test_openai_compatible_json_schema needs the temperature fix:

The two tests use fundamentally different OpenAI API features:

• test_json_schema: Uses "type": "json" (older JSON mode) — does not enforce strict schema adherence, uses best-effort validation
• test_openai_compatible_json_schema: Uses "type": "json_schema" (Structured Outputs) — enforces strict schema conformance using constrained token-level decoding

Structured Outputs uses grammar-based constrained sampling where after every token, the inference engine determines which tokens are valid based on the schema grammar and masks invalid tokens by setting their probability to 0. This token-level constraint is sensitive to non-deterministic sampling behavior from FlashInfer.

JSON mode improves model reliability for generating valid JSON outputs, but does not guarantee that the model's response will conform to a particular schema, making it less sensitive to sampling variability.

The temperature=0.0 fix in test_openai_compatible_json_schema is therefore intentional and appropriate to that specific test variant. There is no evidence that test_json_schema requires the same fix.

Apply temperature=0.0 only to the json_schema variant, as currently implemented. No changes needed.

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[tensorrt-cicd]

PR_Github #25053 [ run ] triggered by Bot. Commit: 15f1eec

[tensorrt-cicd]

PR_Github #25053 [ run ] completed with state SUCCESS. Commit: 15f1eec
/LLM/main/L0_MergeRequest_PR pipeline #18934 completed with status: 'FAILURE'

[ixlmar]

/bot run

[tensorrt-cicd]

PR_Github #25069 [ run ] triggered by Bot. Commit: 15f1eec

[tensorrt-cicd]

PR_Github #25069 [ run ] completed with state SUCCESS. Commit: 15f1eec
/LLM/main/L0_MergeRequest_PR pipeline #18949 completed with status: 'SUCCESS'
Pipeline passed with automatic retried tests. Check the rerun report for details.