Fix FastIntDiv tparam

[aamijar]

Add explicit template parameters for FastIntDiv, follow up to NVIDIA/raft#3059.

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved consistency in soft clustering calculations, helping selected-cluster counts and distance handling behave more reliably.
  • Updated kernel parameter handling to better match the expected value type, reducing the risk of type-related issues during GPU execution.
  • Refreshed copyright year ranges.

Walkthrough

FastIntDiv template instantiations in the HDBSCAN soft clustering kernel declarations and call sites are made explicit by changing FastIntDiv to FastIntDiv<value_idx>, with matching static_cast<value_idx> at call sites. The copyright year is also updated to 2026.

Changes

FastIntDiv explicit template parameter typing

Layer / File(s)	Summary
merge_height_kernel parameter type fix cpp/src/hdbscan/detail/kernels/soft_clustering.cuh	Both overloads change the n parameter from raft::util::FastIntDiv to raft::util::FastIntDiv<value_idx>; copyright year updated to 2026.
Call-site FastIntDiv<value_idx> construction cpp/src/hdbscan/detail/soft_clustering.cuh	reduction_op divisor and both merge_height_kernel launches updated to construct FastIntDiv<value_idx> with explicit static_cast<value_idx>(n_selected_clusters).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly reflects the main change: making the FastIntDiv template parameter explicit.
Description check	✅ Passed	The description is directly related to the changeset and matches the stated FastIntDiv template update.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@cpp/src/hdbscan/detail/soft_clustering.cuh`:
- Around line 175-183: Guard the narrowing of n_selected_clusters before
launching merge_height_kernel and the other affected entry point in
soft_clustering.cuh: both currently pass a size_t through static_cast<value_idx>
for the kernel count and FastIntDiv divisor, which can truncate large values and
break indexing. Replace the unchecked cast with
ML::narrow_cast<value_idx>(n_selected_clusters) at the call sites (or widen the
API if value_idx cannot safely hold the full range), and use the narrowed value
consistently for the launch arguments in merge_height_kernel and the
corresponding second launch site.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 0c1bb20f-834c-462b-8037-faa97ee25d71

📥 Commits

Reviewing files that changed from the base of the PR and between 2c1989f and 9132224.

📒 Files selected for processing (2)

• cpp/src/hdbscan/detail/kernels/soft_clustering.cuh
• cpp/src/hdbscan/detail/soft_clustering.cuh

[coderabbitai]

🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

HIGH: Guard the size_t→value_idx cast before these launches.

Both entry points take n_selected_clusters as size_t, but the new launch arguments narrow it with static_cast<value_idx> for both the kernel count and the FastIntDiv divisor. If that count ever exceeds value_idx, the kernel sees a truncated divisor/count and its row/column indexing becomes invalid.

Suggested fix

+  auto n_selected_clusters_idx = ML::narrow_cast<value_idx>(n_selected_clusters);
   merge_height_kernel<<<n_blocks, tpb, 0, stream>>>(
     merge_heights,
     lambdas,
     ...
-    static_cast<value_idx>(n_selected_clusters),
-    raft::util::FastIntDiv<value_idx>(static_cast<value_idx>(n_selected_clusters)),
+    n_selected_clusters_idx,
+    raft::util::FastIntDiv<value_idx>(n_selected_clusters_idx),
     selected_clusters);

As per path instructions, host-side count/dimension narrowing must use ML::narrow_cast<...>(...) or widen the API.

Also applies to: 281-291

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@cpp/src/hdbscan/detail/soft_clustering.cuh` around lines 175 - 183, Guard the
narrowing of n_selected_clusters before launching merge_height_kernel and the
other affected entry point in soft_clustering.cuh: both currently pass a size_t
through static_cast<value_idx> for the kernel count and FastIntDiv divisor,
which can truncate large values and break indexing. Replace the unchecked cast
with ML::narrow_cast<value_idx>(n_selected_clusters) at the call sites (or widen
the API if value_idx cannot safely hold the full range), and use the narrowed
value consistently for the launch arguments in merge_height_kernel and the
corresponding second launch site.

Source: Path instructions

[jcrist]

[jcrist]

/merge