[cudax][cuco] Migrate host insert_if APIs for fixed_capacity_set

cudax/include/cuda/experimental/__cuco/fixed_capacity_set.cuh

@@ -232,6 +232,54 @@ public:
     __impl_->insert_async(__stream, __first, __last, ref());
   }
 
+  //! @brief Inserts keys whose stencil satisfies `__pred` and returns the number of new keys inserted.
+  //!
+  //! The key `__first[i]` is inserted when `__pred(__stencil[i])` is true. Duplicate keys and keys
+  //! that cannot fit in the set do not contribute to the count.
+  //! @pre No selected input key equals the empty sentinel.
+  //! @note `__pred` may be invoked more than once for the same stencil element.
+  //! @note Synchronizes the supplied stream for nonempty input. For asynchronous execution use `insert_if_async`.
+  //! @throws cuda_error if the operation or stream synchronization fails
+  //! @tparam _InputIt Device-accessible random-access iterator with compatible key values
+  //! @tparam _StencilIt Device-accessible random-access iterator whose values are convertible to the
+  //! predicate's argument type
+  //! @tparam _Predicate Unary callable returning a value convertible to `bool`
+  //! @param[in] __stream Stream used for insertion
+  //! @param[in] __first Beginning of the input range
+  //! @param[in] __last End of the input range
+  //! @param[in] __stencil Beginning of the stencil range
+  //! @param[in] __pred Predicate applied to each stencil value to select keys for insertion
+  //! @return Number of successfully inserted keys
+  template <class _InputIt, class _StencilIt, class _Predicate>
+  _CCCL_HOST_API size_type
+  insert_if(::cuda::stream_ref __stream, _InputIt __first, _InputIt __last, _StencilIt __stencil, _Predicate __pred)
+  {
+    return __impl_->insert_if(__stream, __first, __last, __stencil, __pred, ref());
+  }
+
+  //! @brief Asynchronously inserts keys whose stencil satisfies `__pred` without returning an insertion count.
+  //!
+  //! The key `__first[i]` is inserted when `__pred(__stencil[i])` is true. Duplicate keys and keys
+  //! that cannot fit in the set are ignored.
+  //! @pre No selected input key equals the empty sentinel.
+  //! @note `__pred` may be invoked more than once for the same stencil element.
+  //! @throws cuda_error if insertion fails to launch
+  //! @tparam _InputIt Device-accessible random-access iterator with compatible key values
+  //! @tparam _StencilIt Device-accessible random-access iterator whose values are convertible to the
+  //! predicate's argument type
+  //! @tparam _Predicate Unary callable returning a value convertible to `bool`
+  //! @param[in] __stream Stream used for insertion
+  //! @param[in] __first Beginning of the input range
+  //! @param[in] __last End of the input range
+  //! @param[in] __stencil Beginning of the stencil range
+  //! @param[in] __pred Predicate applied to each stencil value to select keys for insertion
+  template <class _InputIt, class _StencilIt, class _Predicate>
+  _CCCL_HOST_API void insert_if_async(
+    ::cuda::stream_ref __stream, _InputIt __first, _InputIt __last, _StencilIt __stencil, _Predicate __pred)
+  {
+    __impl_->insert_if_async(__stream, __first, __last, __stencil, __pred, ref());
+  }
+
   //! @brief Writes whether each query key is present.
   //!
   //! @pre No query key equals the empty sentinel.

cudax/test/cuco/fixed_capacity_set/test_insert_and_contains.cu

@@ -35,6 +35,14 @@ struct duplicate_key
   }
 };
 
+struct is_negative
+{
+  [[nodiscard]] _CCCL_DEVICE_API bool operator()(int value) const noexcept
+  {
+    return value < 0;
+  }
+};
+
 C2H_TEST("fixed_capacity_set insert and contains", "[container]", key_types, cg_sizes, bucket_sizes, probing_kinds)
 {
   using key_type                              = c2h::get<0, TestType>;
@@ -92,6 +100,19 @@ C2H_TEST("fixed_capacity_set insert and contains", "[container]", key_types, cg_
   set.contains(context.stream, first, first + num_queries, found.begin());
   REQUIRE(context.matches(found.data(), num_queries, num_keys));
 
+  // The stencil is negative only for the first half while every key is nonnegative, so the stencil, not the key,
+  // selects the first half.
+  const auto stencil = cuda::counting_iterator<int>{-num_keys / 2};
+  set.clear(context.stream);
+  REQUIRE(set.insert_if(context.stream, first, first + num_keys, stencil, is_negative{}) == num_keys / 2);
+  set.contains(context.stream, first, first + num_queries, found.begin());
+  REQUIRE(context.matches(found.data(), num_queries, num_keys / 2));
+
+  set.clear(context.stream);
+  set.insert_if_async(context.stream, first, first + num_keys, stencil, is_negative{});
+  set.contains(context.stream, first, first + num_queries, found.begin());
+  REQUIRE(context.matches(found.data(), num_queries, num_keys / 2));
+
   set_type full{context.stream, context.mr, cuda::std::size_t{13}, cudax::cuco::empty_key{static_cast<key_type>(-1)}};
   const int capacity = static_cast<int>(full.capacity());
   REQUIRE(full.insert(context.stream, first, first + capacity) == full.capacity());