Expand MdForwardIter host coverage

[psychocoderHPC]

Split from local commit 6110d5c.

Base branch: dev.

Summary by CodeRabbit

• Bug Fixes

  • Improved const-qualified iterator access for multi-dimensional spans to properly return const iterators.
  • Added const-qualified iterator support to multi-dimensional array containers.

• Tests

  • Expanded test coverage for multi-dimensional array iteration including empty array handling, traversal order validation, const correctness enforcement, and iterator increment behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 51b6511c-2fac-4e41-926d-4f73b4757a23

📥 Commits

Reviewing files that changed from the base of the PR and between 6110d5c and 8995315.

📒 Files selected for processing (3)

• include/alpaka/mem/MdSpan.hpp
• include/alpaka/mem/MdSpanArray.hpp
• test/unit/mem/mdIterator.cpp

🚧 Files skipped from review as they are similar to previous changes (2)

• include/alpaka/mem/MdSpan.hpp
• include/alpaka/mem/MdSpanArray.hpp

---

📝 Walkthrough

Walkthrough

This PR refines iterator access in MdSpan and MdSpanArray classes. The const-qualified begin()/end() methods now construct iterators from getConstMdSpan() instead of *this. New const overloads are added to MdSpanArray. Comprehensive unit tests validate iterator behavior across various container configurations and edge cases.

Changes

Cohort / File(s)	Summary
Iterator const overload updates include/alpaka/mem/MdSpan.hpp, include/alpaka/mem/MdSpanArray.hpp	Updated begin() const and end() const methods to construct iterators from getConstMdSpan() rather than *this. New const overloads added to MdSpanArray.
Iterator test suite expansion test/unit/mem/mdIterator.cpp	Replaced single test with comprehensive Catch2 test suite. Added collectValues helper and multiple test sections covering zero extents, 1D/3D traversal order, mutable/const iteration semantics, and increment behaviors.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 Hopping through spans so true,
Const iterators, fresh and new,
getConstMdSpan leads the way,
Through dimensions, hooray, hooray!
Tests validate each bound we take, 🎉

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ 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%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main changes: expanding test coverage for MdForwardIter (iterator access) on the host platform across MdSpan and MdSpanArray.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch pr-expand-mdforwarditer-host-coverage

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

🧹 Nitpick comments (1)

test/unit/mem/mdIterator.cpp (1)

92-105: Add direct const-iterator checks for MdSpan and MdSpanArray.

The new read-only assertions currently only prove the View path. Adding one const MdSpan and one const MdSpanArray round-trip here would exercise the overloads changed in include/alpaka/mem/MdSpan.hpp and include/alpaka/mem/MdSpanArray.hpp.

➕ Suggested coverage

         std::array<int, 6> storage{2, 4, 6, 8, 10, 12};
         auto view = alpaka::makeView(api::host, storage.data(), alpaka::Vec{2u, 3u});
         auto const constView = view.getConstView();
+        auto span = alpaka::makeMdSpan(storage.data(), alpaka::Vec{2u, 3u});
+        int arrayStorage[2][3]{{2, 4, 6}, {8, 10, 12}};
+        alpaka::MdSpanArray<decltype(arrayStorage), uint32_t> arraySpan(arrayStorage);
 
         static_assert(!std::is_const_v<std::remove_reference_t<decltype(*view.begin())>>);
         static_assert(std::is_const_v<std::remove_reference_t<decltype(*constView.begin())>>);
         static_assert(std::is_const_v<std::remove_reference_t<decltype(*std::as_const(view).begin())>>);
+        static_assert(std::is_const_v<std::remove_reference_t<decltype(*std::as_const(span).begin())>>);
+        static_assert(std::is_const_v<std::remove_reference_t<decltype(*std::as_const(arraySpan).begin())>>);
 
         REQUIRE(collectValues(view) == std::vector<int>{2, 4, 6, 8, 10, 12});
         REQUIRE(collectValues(constView) == collectValues(view));
+        REQUIRE(collectValues(std::as_const(span)) == collectValues(view));
+        REQUIRE(collectValues(std::as_const(arraySpan)) == collectValues(view));

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@test/unit/mem/mdIterator.cpp` around lines 92 - 105, Add tests that exercise
the const-iterator overloads for MdSpan and MdSpanArray: create a mutable MdSpan
and MdSpanArray from the same storage used for View, obtain their const variants
(e.g., via getConstView-like API or by binding to const MdSpan/MdSpanArray), add
static_asserts that *const* iterators yield const references (similar to the
View checks) and REQUIRE that collectValues(constMdSpan) and
collectValues(constMdSpanArray) equal the mutable collectValues results; target
the types MdSpan and MdSpanArray and the helper collectValues to ensure the
MdSpan.hpp and MdSpanArray.hpp const overloads are exercised.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@test/unit/mem/mdIterator.cpp`:
- Around line 92-105: Add tests that exercise the const-iterator overloads for
MdSpan and MdSpanArray: create a mutable MdSpan and MdSpanArray from the same
storage used for View, obtain their const variants (e.g., via getConstView-like
API or by binding to const MdSpan/MdSpanArray), add static_asserts that *const*
iterators yield const references (similar to the View checks) and REQUIRE that
collectValues(constMdSpan) and collectValues(constMdSpanArray) equal the mutable
collectValues results; target the types MdSpan and MdSpanArray and the helper
collectValues to ensure the MdSpan.hpp and MdSpanArray.hpp const overloads are
exercised.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 5e7c9b73-9f14-491e-a025-c3dec5d07b04

📥 Commits

Reviewing files that changed from the base of the PR and between 33568ee and 6110d5c.

📒 Files selected for processing (5)

• include/alpaka/mem/MdSpan.hpp
• include/alpaka/mem/MdSpanArray.hpp
• test/unit/mem/concepts.cpp
• test/unit/mem/idxRange.cpp
• test/unit/mem/mdIterator.cpp

[psychocoderHPC]

@coderabbitai review

[coderabbitai]

✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[psychocoderHPC]

@coderabbitai review

[coderabbitai]

✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.