[INFRA] Import NVIDIA/CCCL upstream as optimization reference library

CCCL (CUDA C++ Core Libraries) provides:
- CUB: device/block/warp-level GPU primitives (reduce, scan, sort, topk)
- Thrust: high-level parallel algorithms (transform_reduce, sort, scan)
- libcudacxx: CUDA C++ standard library (atomics, barriers, memory)
- cudax: experimental features (memory resources, allocators)
- Tuning policies: per-SM hardware-specific algorithm parameters

Competition optimization vectors mapped to CCCL:
- Output TPS (83% weight): warp_reduce, block_reduce, device_topk
- Input TPS (14% weight): device_scan, block_load, prefetch
- Cache TPS (3% weight): prefix caching strategy patterns
- Memory (0.9 util): pooled/cached/buddy allocators

Source: https://github.com/NVIDIA/cccl (shallow clone, HEAD only)
License: Apache-2.0

cccl_upstream/thrust/testing/count.cu

@@ -0,0 +1,128 @@
+#include <thrust/count.h>
+#include <thrust/iterator/retag.h>
+
+#include <unittest/unittest.h>
+
+template <class Vector>
+void TestCountSimple()
+{
+  Vector data{1, 1, 0, 0, 1};
+
+  ASSERT_EQUAL(thrust::count(data.begin(), data.end(), 0), 2);
+  ASSERT_EQUAL(thrust::count(data.begin(), data.end(), 1), 3);
+  ASSERT_EQUAL(thrust::count(data.begin(), data.end(), 2), 0);
+}
+DECLARE_VECTOR_UNITTEST(TestCountSimple);
+
+template <typename T>
+void TestCount(const size_t n)
+{
+  thrust::host_vector<T> h_data   = unittest::random_samples<T>(n);
+  thrust::device_vector<T> d_data = h_data;
+
+  size_t cpu_result = thrust::count(h_data.begin(), h_data.end(), T(5));
+  size_t gpu_result = thrust::count(d_data.begin(), d_data.end(), T(5));
+
+  ASSERT_EQUAL(cpu_result, gpu_result);
+}
+DECLARE_VARIABLE_UNITTEST(TestCount);
+
+template <typename T>
+struct greater_than_five
+{
+  _CCCL_HOST_DEVICE bool operator()(const T& x) const
+  {
+    return x > 5;
+  }
+};
+
+template <class Vector>
+void TestCountIfSimple()
+{
+  using T = typename Vector::value_type;
+
+  Vector data{1, 6, 1, 9, 2};
+
+  ASSERT_EQUAL(thrust::count_if(data.begin(), data.end(), greater_than_five<T>()), 2);
+}
+DECLARE_VECTOR_UNITTEST(TestCountIfSimple);
+
+template <typename T>
+void TestCountIf(const size_t n)
+{
+  thrust::host_vector<T> h_data   = unittest::random_samples<T>(n);
+  thrust::device_vector<T> d_data = h_data;
+
+  size_t cpu_result = thrust::count_if(h_data.begin(), h_data.end(), greater_than_five<T>());
+  size_t gpu_result = thrust::count_if(d_data.begin(), d_data.end(), greater_than_five<T>());
+
+  ASSERT_EQUAL(cpu_result, gpu_result);
+}
+DECLARE_VARIABLE_UNITTEST(TestCountIf);
+
+template <typename Vector>
+void TestCountFromConstIteratorSimple()
+{
+  Vector data{1, 1, 0, 0, 1};
+
+  ASSERT_EQUAL(thrust::count(data.cbegin(), data.cend(), 0), 2);
+  ASSERT_EQUAL(thrust::count(data.cbegin(), data.cend(), 1), 3);
+  ASSERT_EQUAL(thrust::count(data.cbegin(), data.cend(), 2), 0);
+}
+DECLARE_VECTOR_UNITTEST(TestCountFromConstIteratorSimple);
+
+template <typename InputIterator, typename EqualityComparable>
+int count(my_system& system, InputIterator, InputIterator, EqualityComparable x)
+{
+  system.validate_dispatch();
+  return x;
+}
+
+void TestCountDispatchExplicit()
+{
+  thrust::device_vector<int> vec(1);
+
+  my_system sys(0);
+  thrust::count(sys, vec.begin(), vec.end(), 13);
+
+  ASSERT_EQUAL(true, sys.is_valid());
+}
+DECLARE_UNITTEST(TestCountDispatchExplicit);
+
+template <typename InputIterator, typename EqualityComparable>
+int count(my_tag, InputIterator /*first*/, InputIterator, EqualityComparable x)
+{
+  return x;
+}
+
+void TestCountDispatchImplicit()
+{
+  thrust::device_vector<int> vec(1);
+
+  auto result = thrust::count(thrust::retag<my_tag>(vec.begin()), thrust::retag<my_tag>(vec.end()), 13);
+
+  ASSERT_EQUAL(13, result);
+}
+DECLARE_UNITTEST(TestCountDispatchImplicit);
+
+void TestCountWithBigIndexesHelper(int magnitude)
+{
+  thrust::counting_iterator<long long> begin(1);
+  thrust::counting_iterator<long long> end = begin + (1ll << magnitude);
+  ASSERT_EQUAL(::cuda::std::distance(begin, end), 1ll << magnitude);
+
+  long long result = thrust::count(thrust::device, begin, end, (1ll << magnitude) - 17);
+
+  ASSERT_EQUAL(result, 1);
+}
+
+void TestCountWithBigIndexes()
+{
+  TestCountWithBigIndexesHelper(30);
+#ifndef THRUST_FORCE_32_BIT_OFFSET_TYPE
+  TestCountWithBigIndexesHelper(31);
+  TestCountWithBigIndexesHelper(32);
+  TestCountWithBigIndexesHelper(33);
+#endif
+}
+DECLARE_UNITTEST(TestCountWithBigIndexes);