[TRTLLM-8425][doc] Update sampling documentation

[stnie]

Summary by CodeRabbit

• Documentation
  • Comprehensively updated sampling features documentation with clearer descriptions and reorganized content layout.
  • Documented new sampler_type parameter for explicit backend selection (TorchSampler or TRTLLMSampler).
  • Added detailed explanation of default backend auto-selection behavior for different use cases.
  • Updated all examples demonstrating per-prompt sampling configuration and multi-sampling usage.
  • Simplified beam search prerequisites and setup instructions.

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Description

Update docs for sampling

Test Coverage

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[zhenhuaw-me]

Added a few comments as a beginner of sampling :)

[coderabbitai]

📝 Walkthrough

Walkthrough

Documentation rewrite reorganizes sampling features guide with combined feature table, updates terminology (PyTorch to Torch), replaces enable_trtllm_sampler guidance with explicit sampler_type parameter selection, adds default auto-selection behavior explanation, updates examples for per-prompt sampling parameters, and removes beam search prerequisites.

Changes

Cohort / File(s)

Summary

Sampling Documentation Rewrite docs/source/features/sampling.md

Reorganized content into combined feature table (Forward Pass, Sampling Strategies, Sampling Features); updated PyTorch terminology to Torch; replaced enable_trtllm_sampler guidance with explicit sampler_type parameter ("TorchSampler"/"TRTLLMSampler"); added default auto-selection behavior (TRTLLM for Beam Search, Torch otherwise); updated examples with per-prompt SamplingParams; removed speculative decoder unsupported note; removed disable_overlap_scheduler and CUDA Graphs prerequisites from beam search; added per-prompt configuration code blocks.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	PR description is minimal and lacks required details. Only states 'Update docs for sampling' without explaining the issue, motivation, or specific changes made.	Expand description to include: what was updated in the sampling documentation, why the changes were necessary, and details about the new sampler backends and API changes (sampler_type parameter, per-prompt configuration, etc.).

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: updating sampling documentation. It follows the required format with JIRA ticket [TRTLLM-8425], type [doc], and a concise summary.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 2

Fix all issues with AI Agents 🤖

In @docs/source/features/sampling.md:
- Line 24: Replace the phrase "long term solution" with the hyphenated compound
adjective "long-term solution" in the sentence that reads "Torch Sampler
currently supports a superset of features of TRTLLM Sampler, and is intended as
the long term solution." Ensure the updated sentence uses "long-term solution"
so the compound adjective correctly modifies "solution."
- Line 3: Replace the incorrect capitalization "Pytorch" with the correct
product name "PyTorch" in the documentation; specifically update the string "The
Pytorch backend supports a wide variety of features, listed below:" to "The
PyTorch backend supports a wide variety of features, listed below:" and scan the
same file for any other occurrences of "Pytorch" to correct them for consistent
capitalization.

🧹 Nitpick comments (1)

docs/source/features/sampling.md (1)

1-41: Clarify the relationship between PyTorch backend and the two samplers.

The opening states the documentation covers the "Pytorch backend," but the "General usage" section introduces two sampling backends: Torch Sampler and TRTLLM Sampler. The distinction between the backend and the samplers could be clearer. Consider explicitly stating whether both samplers are part of the PyTorch backend or if they represent different architectural choices.

📜 Review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between b1733d5 and 8340ae6.

📒 Files selected for processing (1)

• docs/source/features/sampling.md

🧰 Additional context used

🧠 Learnings (11)

📓 Common learnings

Learnt from: venkywonka
Repo: NVIDIA/TensorRT-LLM PR: 6029
File: .github/pull_request_template.md:45-53
Timestamp: 2025-08-27T17:50:13.264Z
Learning: For PR templates in TensorRT-LLM, avoid suggesting changes that would increase developer overhead, such as converting plain bullets to mandatory checkboxes. The team prefers guidance-style bullets that don't require explicit interaction to reduce friction in the PR creation process.

Learnt from: tongyuantongyu
Repo: NVIDIA/TensorRT-LLM PR: 9655
File: tensorrt_llm/_torch/pyexecutor/sampler.py:3031-3031
Timestamp: 2025-12-12T03:27:18.859Z
Learning: In tensorrt_llm/_torch/pyexecutor/sampler.py, when reviewing code that iterates through requests, ensure it does not convert excessive data into Python lists. Instead, the code should use torch.gather or indexing to gather only the data that will be used in the for loop before converting to Python lists. This minimizes data movement and improves performance.

Learnt from: dcampora
Repo: NVIDIA/TensorRT-LLM PR: 6867
File: tensorrt_llm/_torch/pyexecutor/sampler.py:67-72
Timestamp: 2025-08-13T16:20:37.987Z
Learning: In TensorRT-LLM sampler code, performance is prioritized over additional validation checks. The beam_width helper method intentionally returns the first request's beam_width without validating consistency across all requests to avoid performance overhead from iterating through the entire batch.

📚 Learning: 2025-08-27T15:03:57.149Z

Learnt from: ixlmar
Repo: NVIDIA/TensorRT-LLM PR: 7294
File: tensorrt_llm/_torch/pyexecutor/sampler.py:368-392
Timestamp: 2025-08-27T15:03:57.149Z
Learning: In TensorRT-LLM's sampler.py, int32 usage for softmax_indices and related tensor indexing is intentional and should not be changed to int64. The torch.IntTensor type hint is correct for the sample() function's softmax_indices parameter.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-08-13T16:20:37.987Z

Learnt from: dcampora
Repo: NVIDIA/TensorRT-LLM PR: 6867
File: tensorrt_llm/_torch/pyexecutor/sampler.py:67-72
Timestamp: 2025-08-13T16:20:37.987Z
Learning: In TensorRT-LLM sampler code, performance is prioritized over additional validation checks. The beam_width helper method intentionally returns the first request's beam_width without validating consistency across all requests to avoid performance overhead from iterating through the entire batch.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-07-28T17:06:08.621Z

Learnt from: moraxu
Repo: NVIDIA/TensorRT-LLM PR: 6303
File: tests/integration/test_lists/qa/examples_test_list.txt:494-494
Timestamp: 2025-07-28T17:06:08.621Z
Learning: In TensorRT-LLM testing, it's common to have both CLI flow tests (test_cli_flow.py) and PyTorch API tests (test_llm_api_pytorch.py) for the same model. These serve different purposes: CLI flow tests validate the traditional command-line workflow, while PyTorch API tests validate the newer LLM API backend. Both are legitimate and should coexist.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-08-14T15:38:01.771Z

Learnt from: MatthiasKohl
Repo: NVIDIA/TensorRT-LLM PR: 6904
File: cpp/tensorrt_llm/pybind/thop/bindings.cpp:55-57
Timestamp: 2025-08-14T15:38:01.771Z
Learning: In TensorRT-LLM Python bindings, tensor parameter collections like mla_tensor_params and spec_decoding_tensor_params are kept as required parameters without defaults to maintain API consistency, even when it might affect backward compatibility.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-08-15T06:46:53.813Z

Learnt from: eopXD
Repo: NVIDIA/TensorRT-LLM PR: 6767
File: cpp/tensorrt_llm/batch_manager/kvCacheManager.cpp:0-0
Timestamp: 2025-08-15T06:46:53.813Z
Learning: In the TensorRT-LLM KV cache manager, SWA (Sliding Window Attention) combined with beam search is currently in a broken/non-functional state and is planned for future rework. During preparatory refactoring phases, code related to SWA+beam search may intentionally remain in a non-working state until the broader rework is completed.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-08-26T09:37:10.463Z

Learnt from: jiaganc
Repo: NVIDIA/TensorRT-LLM PR: 7031
File: tensorrt_llm/bench/dataclasses/configuration.py:90-104
Timestamp: 2025-08-26T09:37:10.463Z
Learning: In TensorRT-LLM, the `get_pytorch_perf_config()` method returns `self.pytorch_config` which can contain default `cuda_graph_config` values, so `llm_args` may already have this config before the extra options processing.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-08-26T09:37:10.463Z

Learnt from: jiaganc
Repo: NVIDIA/TensorRT-LLM PR: 7031
File: tensorrt_llm/bench/dataclasses/configuration.py:90-104
Timestamp: 2025-08-26T09:37:10.463Z
Learning: In TensorRT-LLM's bench configuration, the `get_pytorch_perf_config()` method returns `self.pytorch_config` which is a Dict[str, Any] that can contain default values including `cuda_graph_config`, making the fallback `llm_args["cuda_graph_config"]` safe to use.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-08-14T15:43:23.107Z

Learnt from: MatthiasKohl
Repo: NVIDIA/TensorRT-LLM PR: 6904
File: tensorrt_llm/_torch/attention_backend/trtllm.py:259-262
Timestamp: 2025-08-14T15:43:23.107Z
Learning: In TensorRT-LLM's attention backend, tensor parameters in the plan() method are assigned directly without validation (dtype, device, contiguity checks). This maintains consistency across all tensor inputs and follows the pattern of trusting callers to provide correctly formatted tensors.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-09-09T09:40:45.658Z

Learnt from: fredricz-20070104
Repo: NVIDIA/TensorRT-LLM PR: 7645
File: tests/integration/test_lists/qa/llm_function_core.txt:648-648
Timestamp: 2025-09-09T09:40:45.658Z
Learning: In TensorRT-LLM test lists, it's common and intentional for the same test to appear in multiple test list files when they serve different purposes (e.g., llm_function_core.txt for comprehensive core functionality testing and llm_function_core_sanity.txt for quick sanity checks). This duplication allows tests to be run in different testing contexts.

Applied to files:

• docs/source/features/sampling.md

📚 Learning: 2025-08-01T15:14:45.673Z

Learnt from: yibinl-nvidia
Repo: NVIDIA/TensorRT-LLM PR: 6506
File: examples/models/core/mixtral/requirements.txt:3-3
Timestamp: 2025-08-01T15:14:45.673Z
Learning: In TensorRT-LLM, examples directory can have different dependency versions than the root requirements.txt file. Version conflicts between root and examples dependencies are acceptable because examples are designed to be standalone and self-contained.

Applied to files:

• docs/source/features/sampling.md

🪛 LanguageTool

docs/source/features/sampling.md

[grammar] ~24-~24: Use a hyphen to join words.
Context: ...LLM Sampler, and is intended as the long term solution. One can specify which sam...

(QB_NEW_EN_HYPHEN)

🔇 Additional comments (1)

docs/source/features/sampling.md (1)

45-74: Well-structured examples addressing previous review feedback.

The examples effectively demonstrate both single and per-prompt sampling parameter usage, directly addressing previous reviewer comments about showing per-prompt configuration. The progression from basic usage to advanced per-prompt specification is clear and helpful.

[stnie]

/bot run --stage-list "A10-Build_Docs"

[tensorrt-cicd]

PR_Github #31593 [ run ] triggered by Bot. Commit: 8340ae6

[tensorrt-cicd]

PR_Github #31593 [ run ] completed with state SUCCESS. Commit: 8340ae6
/LLM/main/L0_MergeRequest_PR pipeline #24432 (Partly Tested) completed with status: 'SUCCESS'

[nv-guomingz]

LGTM

[stnie]

/bot skip --comment "doc-only change"

[tensorrt-cicd]

PR_Github #31767 [ skip ] triggered by Bot. Commit: 8340ae6

[tensorrt-cicd]

PR_Github #31767 [ skip ] completed with state SUCCESS. Commit: 8340ae6
Skipping testing for commit 8340ae6

[stnie]

/bot run --stage-list "A10-Build_Docs"

[tensorrt-cicd]

PR_Github #32004 [ run ] triggered by Bot. Commit: d8bd34f

[tensorrt-cicd]

PR_Github #32004 [ run ] completed with state SUCCESS. Commit: d8bd34f
/LLM/main/L0_MergeRequest_PR pipeline #24796 (Partly Tested) completed with status: 'SUCCESS'

[stnie]

/bot skip --comment "doc-only change"

[tensorrt-cicd]

PR_Github #32269 [ skip ] triggered by Bot. Commit: d8bd34f

[tensorrt-cicd]

PR_Github #32269 [ skip ] completed with state SUCCESS. Commit: d8bd34f
Skipping testing for commit d8bd34f