[CongMa13]

Refactor cd sequence_reverse_inclusive_scan from recursive template to constexpr for-loop.

This pull request improves the utility array functionality and its integration with sequence utilities, as well as adds comprehensive unit tests for the Array class. The main changes include refactoring the implementation of reverse inclusive scan for sequences, updating header dependencies, optimizing the Array assignment operator, and introducing a full test suite for Array.

Array and Sequence Utility Improvements:

• Refactored the implementation of sequence_reverse_inclusive_scan in sequence.hpp to use a more efficient, array-based approach, encapsulated in a new impl namespace. This change simplifies the logic and should improve compile-time performance.
• Updated header dependencies in both array.hpp and sequence.hpp to remove unused includes and ensure correct dependency order, notably including array.hpp in sequence.hpp to support the new scan implementation. [1] [2]
• Optimized the assignment operator in the Array struct by replacing the static_for loop with a standard for-loop and adding a pragma for potential unrolling, improving both readability and performance.

Testing Enhancements:

• Added a new unit test file unit_array.cpp with comprehensive tests covering construction, element access, assignment, iterators, the make_array helper, and different data types for the Array class.
• Updated the CMakeLists.txt to build and link the new unit_array test executable.

Tracking issue: #3575

[CongMa13]

Removed the dependency on static_for. Hence, only need to include type.hpp.

And the code is easier to read.

[Copilot]

Pull request overview

This PR refactors the sequence_reverse_inclusive_scan implementation from a recursive template-based approach to a more efficient constexpr for-loop using the Array utility class. The changes improve compile-time performance and simplify the logic.

Changes:

• Refactored sequence_reverse_inclusive_scan to use an array-based iterative approach instead of recursive templates
• Updated header dependencies to remove circular includes and optimize dependencies
• Optimized Array::operator= by replacing static_for with a standard for-loop with unroll pragma
• Added comprehensive unit tests for the Array class

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
include/ck/utility/sequence.hpp	Refactored sequence_reverse_inclusive_scan from recursive templates to constexpr array-based implementation
include/ck/utility/array.hpp	Updated header dependencies and optimized assignment operator with standard for-loop
test/util/unit_array.cpp	Added comprehensive unit tests covering Array construction, access, assignment, iterators, and edge cases
test/util/CMakeLists.txt	Added build configuration for new unit_array test executable

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[Copilot]

Comment mentions 'Sequence' but should refer to 'Array' since this test is for the Array class.

Suggested change

	// Test basic Sequence construction and properties
	// Test basic Array construction and properties

[shumway]

This comment should be updated.

[Copilot]

The loop variable uses int type while NSize is of type index_t (typically size_t or similar). For consistency and to avoid potential type conversion issues, use index_t i = 0 instead of int i = 0.

Suggested change

	for(int i = 0; i < NSize; i++)
	for(index_t i = 0; i < NSize; i++)

[shumway]

Yes, let's use index_t for consistency.

[shumway]

We don't need pragma unroll here. The compiler should optimize correctly.

[shumway]

It might be slightly faster to replace this lambda with a named constexpr function helper.

[shumway]

This looks great. I just have a few small comments.

I think we may need unit tests for the reverse inclusive scan.

[illsilin]

Hey @CongMa13, please resolve conflicts for the headers, and make sure ci tests pass.

[ammallya]

Imported to ROCm/rocm-libraries