[PointKernel]

Description

Closes #11135.

This PR migrates the host contains_if and contains_if_async APIs from cuCollections static_set to fixed_capacity_set, reusing the shared open-addressing implementation.

Checklist

• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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[PointKernel]

/ok to test

[coderabbitai]

No actionable comments were generated in the recent review.

Summary

Summary by CodeRabbit

• New Features
  • Added conditional membership checks for fixed-capacity sets, with synchronous and asynchronous options. A predicate selects which queries are checked against the set; unselected queries return false.
• Tests
  • Added coverage for conditional lookups with offset stencil values, including results before and after inserting keys, and verified that only selected queries receive membership results.

Adds synchronous and asynchronous contains_if APIs to fixed_capacity_set. The APIs use a predicate on stencil values to select queries and write membership results. Tests cover both overloads and verify results across the query range.

Changes: Conditional lookup

Layer / File(s)	Summary
Add conditional lookup APIs cudax/include/cuda/experimental/__cuco/fixed_capacity_set.cuh	Adds synchronous and asynchronous contains_if overloads. Both write membership results for selected keys and false for unselected keys. The synchronous overload synchronizes the supplied stream; the asynchronous overload does not.
Test conditional lookup cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu	Adds predicate helpers and tests both overloads with an offset stencil. Checks membership results for even-indexed inserted keys.

Assessment against linked issues

Objective	Addressed	Explanation
Migrate host contains_if APIs to fixed_capacity_set and add corresponding tests [#11135]	✅

Possibly related PRs

• NVIDIA/cccl#12355: Adds stencil-filtered lookup APIs that return stored keys or a sentinel rather than membership results.

Suggested reviewers: fbusato

Change: Feature

Merge Risk: Low · up to 41473

The change is mergeable with a test follow-up: the filtered lookup test does not detect every missing write, but no current API failure or build blocker is established.

Security architecture risk: Minimal · up to 41473

The new queries reuse existing lookup execution and preserve caller-managed storage and stream synchronization. The review found no introduced security finding or material expansion of privileges or trust-boundary exposure.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The added API operates with the invoking application's existing CUDA authority over supplied iterators, set storage, and stream. The inspected change adds query selection, not a service, tenant, credential, or sandbox boundary.

Trust Boundaries and Controls

• inferred — The stencil predicate is caller-supplied query logic, not an authorization control. As with existing membership operations, the caller must provide valid device-accessible ranges and retain storage until queued work completes; the new wrappers do not validate untrusted pointers or transfer storage ownership.

Resilience and Maintainability Implications

• inferred — The methods preserve the existing borrowed-storage execution model. Repeated queries do not introduce a set-state transition, while overlapping output writes and premature destruction still require caller coordination. Launch and synchronization errors are reported, but callers must not assume atomic output publication or rollback after execution failure; that limitation predates these wrappers.

- [ ] Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

Recent review info

Run configuration

• Source mode: Auto
• Repository: NVIDIA/cccl
• Branch: main
• File: .coderabbit.yaml
• Commit: 22bbd61
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Enterprise
• Run ID: 4e351f9f-542f-4f62-8e2d-8784ae5d033b

Commits

Reviewing files that changed from the base of the PR and between de7680b and 414731d.

Files selected for processing: 2

• cudax/include/cuda/experimental/__cuco/fixed_capacity_set.cuh
• cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu

Included review availability: This review used your included allowance. Your plan provides up to 12 included reviews per hour; 11 remain after this review.

[coderabbitai]

Actionable comments posted: 1

Nitpick comments: 1

cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu: 1

90-99: Trivial · Maintainability & Code Quality · Quick win

suggestion: Initialize the filtered output before the lookup.

Selected positions already contain the expected membership values. A regression that leaves those positions unchanged can pass this assertion.

Suggested fix

-  set.contains_if(context.stream, first, first + num_queries, stencil, is_odd{}, found.begin());
+  auto filtered_found = cuda::make_buffer<int>(context.stream, context.mr, num_queries, 7);
+  set.contains_if(context.stream, first, first + num_queries, stencil, is_odd{}, filtered_found.begin());
   REQUIRE(cuda::std::all_of(
     context.policy(),
     cuda::counting_iterator<int>{0},
     cuda::counting_iterator<int>{num_queries},
-    matches_even_membership{found.data(), num_keys}));
+    matches_even_membership{filtered_found.data(), num_keys}));

Review info

Run configuration

• Source mode: Auto
• Repository: NVIDIA/cccl
• Branch: main
• File: .coderabbit.yaml
• Commit: dd063b7
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Enterprise
• Run ID: 3ccb783e-2a6a-46f6-a52d-636a2e0925bd

Commits

Reviewing files that changed from the base of the PR and between 83458af and de7680b.

Files selected for processing: 2

• cudax/include/cuda/experimental/__cuco/fixed_capacity_set.cuh
• cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu

Included review availability: This review used your included allowance. Your plan provides up to 12 included reviews per hour; 9 remain after this review.

[coderabbitai]

Major · Functional Correctness · Quick win

Supported by static analysis

Script executed:

sed -n '55,150p' cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu
rg -n 'test_insert_and_contains|define C2H_TEST' cudax/test/cuco

Repository: NVIDIA/cccl

Length of output: 5337

---

Script executed:

cat -n cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu | sed -n '1,185p'
cat -n cudax/test/cuco/fixed_capacity_set/CMakeLists.txt
cat -n cudax/test/cuco/CMakeLists.txt
rg -n --glob '*.[ch]' --glob '*.cuh' --glob '*.hpp' '#[[:space:]]*define[[:space:]]+C2H_TEST' cudax c2h libcudacxx thrust cub 2>/dev/null
git diff dd063b73e63e18f911182f79879fbf7d558ebe79 de7680b3b25b53bca9e8c3bd99bc3401269de02b -- cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu

Repository: NVIDIA/cccl

Length of output: 14218

---

Script executed:

cat -n c2h/include/c2h/catch2_test_helper.h | sed -n '625,660p'
rg -n 'function\(cudax_add_catch2_test|macro\(cudax_add_catch2_test' cudax

Repository: NVIDIA/cccl

Length of output: 1859

---

Script executed:

cat -n cudax/test/CMakeLists.txt | sed -n '1,105p'

Repository: NVIDIA/cccl

Length of output: 3712

---

important: Give the stencil variables distinct names.

The two stencil declarations share a scope, so the test target cannot compile. Rename the later variable and its uses.

Suggested fix

-  const auto stencil = cuda::counting_iterator<int>{-num_keys / 2};
+  const auto insert_stencil = cuda::counting_iterator<int>{-num_keys / 2};
@@
-  REQUIRE(set.insert_if(context.stream, first, first + num_keys, stencil, is_negative{}) == num_keys / 2);
+  REQUIRE(set.insert_if(context.stream, first, first + num_keys, insert_stencil, is_negative{}) == num_keys / 2);
@@
-  set.insert_if_async(context.stream, first, first + num_keys, stencil, is_negative{});
+  set.insert_if_async(context.stream, first, first + num_keys, insert_stencil, is_negative{});

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