Replace optional<unique_ptr> with unique_ptr for heuristics

[wujingyue]

Summary: std::optional<std::unique_ptr<T>> is redundant since unique_ptr can represent "no value" via nullptr.

Changes:

• getMaybeHeuristicsFor / getMaybeHeuristicParams now return std::unique_ptr<T> (nullptr when unavailable).
• Call sites: .has_value() → != nullptr, removed valueOrError for heuristics path.
• FusionKernelRuntime constructor uses NVF_ERROR(heuristics_ != nullptr) after getMaybeHeuristicsFor.

Files: fusion_kernel_runtime.{h,cpp}, fusion_segmenter.{h,cpp}, fusion_executor_cache.cpp, benchmarks (heuristic_*.cpp, shape_inference.cpp).

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[greptile-apps]

Greptile Summary

Removed redundancy by replacing std::optional<std::unique_ptr<T>> with std::unique_ptr<T> throughout the heuristics API, since unique_ptr inherently represents "no value" via nullptr.

Key changes:

• getMaybeHeuristicsFor and getMaybeHeuristicParams now return std::unique_ptr<T> directly
• Null checks updated from .has_value() to != nullptr and std::nullopt to nullptr
• Removed unnecessary .value() extractions when accessing the pointers
• Modernized code to use std::ranges::find_if and std::ranges::find
• Added (void)_ in benchmark loops to suppress unused variable warnings
• Changed debug output from std::endl to '\n' for minor performance improvement

All changes are semantically equivalent and maintain the same behavior. The refactoring simplifies the API and improves code readability.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• Clean refactoring that eliminates redundant type wrapping. All conversions are correct and consistent across the codebase. The changes are semantically equivalent to the original code with no behavioral modifications. Code modernization to C++20 ranges and minor improvements are appropriate.
• No files require special attention

Important Files Changed

Filename	Overview
csrc/runtime/fusion_kernel_runtime.h	Updated return type from optional<unique_ptr> to unique_ptr for getMaybeHeuristicsFor, updated comments to reflect nullptr instead of nullopt
csrc/runtime/fusion_kernel_runtime.cpp	Refactored to use unique_ptr directly, simplified null checks from .has_value() to != nullptr, removed .value() extractions
csrc/runtime/fusion_executor_cache.cpp	Updated lambda to assign unique_ptr directly, modernized to use std::ranges::find_if, changed debug output from std::endl to '\n'
csrc/fusion_segmenter.h	Updated return type and comments for getMaybeHeuristicParams, modernized isFusionInput to use std::ranges::find, added algorithm header
csrc/fusion_segmenter.cpp	Changed return type to unique_ptr, replaced std::nullopt with nullptr

_{Last reviewed commit: 852bd0c}

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[github-actions]

Review updated until commit 852bd0c

Description

• Replace std::optional<std::unique_ptr<T>> with std::unique_ptr<T> for heuristic functions since unique_ptr can represent "no value" via nullptr

• Update return statements from std::nullopt to nullptr in getMaybeHeuristicsFor and getMaybeHeuristicParams

• Update call sites: .has_value() checks changed to != nullptr, removed .value() calls

• Minor formatting: changed std::endl to '\n' in debug output, added (void)_ to suppress benchmark warnings

Changes walkthrough

	Relevant files

PR Reviewer Guide

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🧪 PR contains tests

⚡ Recommended focus areas for review

Missing include for std::ranges The code at line 618 uses std::ranges::find_if but there is no visible #include added to this file. While it may be included indirectly through other headers, it should be verified that the build passes and the include is explicit if not guaranteed by existing includes. // Generate metadata for the fusion's outputs auto group_runtime_outputs = inferOutputMetaTensor( heuristics.get(), group_to_run, group_runtime_inputs, evaluator_precomputed_values.get()); Documentation inconsistency The documentation at lines 128-129 says "will return nullptr if either any segment cannot be scheduled or the parameters don't match" but doesn't mention the case when the segmented fusion has no groups (is empty). This should be clarified to ensure all return nullptr cases are documented. // Try to compute heuristics based on the SegmentedFusion managed // in this kernel runtime, and will return nullptr if either // any segment cannot be scheduled or the parameters don't match. // // Heuristics must use the index type of forced_index_type if given. std::unique_ptr<HeuristicParamsList> getMaybeHeuristicsFor( const KernelArgumentHolder& args, std::optional<PrimDataType> forced_index_type = std::nullopt);

[wujingyue]

!test