[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/sort.cu

@@ -0,0 +1,128 @@
+#include <thrust/functional.h>
+#include <thrust/iterator/retag.h>
+#include <thrust/sort.h>
+
+#include <unittest/unittest.h>
+
+template <typename RandomAccessIterator>
+void sort(my_system& system, RandomAccessIterator, RandomAccessIterator)
+{
+  system.validate_dispatch();
+}
+
+void TestSortDispatchExplicit()
+{
+  thrust::device_vector<int> vec(1);
+
+  my_system sys(0);
+  thrust::sort(sys, vec.begin(), vec.begin());
+
+  ASSERT_EQUAL(true, sys.is_valid());
+}
+DECLARE_UNITTEST(TestSortDispatchExplicit);
+
+template <typename RandomAccessIterator>
+void sort(my_tag, RandomAccessIterator first, RandomAccessIterator)
+{
+  *first = 13;
+}
+
+void TestSortDispatchImplicit()
+{
+  thrust::device_vector<int> vec(1);
+
+  thrust::sort(thrust::retag<my_tag>(vec.begin()), thrust::retag<my_tag>(vec.begin()));
+
+  ASSERT_EQUAL(13, vec.front());
+}
+DECLARE_UNITTEST(TestSortDispatchImplicit);
+
+template <class Vector>
+void InitializeSimpleKeySortTest(Vector& unsorted_keys, Vector& sorted_keys)
+{
+  unsorted_keys.resize(7);
+  unsorted_keys = {1, 3, 6, 5, 2, 0, 4};
+
+  sorted_keys.resize(7);
+  sorted_keys = {0, 1, 2, 3, 4, 5, 6};
+}
+
+template <class Vector>
+void TestSortSimple()
+{
+  Vector unsorted_keys;
+  Vector sorted_keys;
+
+  InitializeSimpleKeySortTest(unsorted_keys, sorted_keys);
+
+  thrust::sort(unsorted_keys.begin(), unsorted_keys.end());
+
+  ASSERT_EQUAL(unsorted_keys, sorted_keys);
+}
+DECLARE_VECTOR_UNITTEST(TestSortSimple);
+
+template <typename T>
+void TestSortAscendingKey(const size_t n)
+{
+  thrust::host_vector<T> h_data   = unittest::random_integers<T>(n);
+  thrust::device_vector<T> d_data = h_data;
+
+  thrust::sort(h_data.begin(), h_data.end(), ::cuda::std::less<T>());
+  thrust::sort(d_data.begin(), d_data.end(), ::cuda::std::less<T>());
+
+  ASSERT_EQUAL(h_data, d_data);
+}
+DECLARE_VARIABLE_UNITTEST(TestSortAscendingKey);
+
+void TestSortDescendingKey()
+{
+  const size_t n = 10027;
+
+  thrust::host_vector<int> h_data   = unittest::random_integers<int>(n);
+  thrust::device_vector<int> d_data = h_data;
+
+  thrust::sort(h_data.begin(), h_data.end(), ::cuda::std::greater<int>());
+  thrust::sort(d_data.begin(), d_data.end(), ::cuda::std::greater<int>());
+
+  ASSERT_EQUAL(h_data, d_data);
+}
+DECLARE_UNITTEST(TestSortDescendingKey);
+
+void TestSortBool()
+{
+  const size_t n = 10027;
+
+  thrust::host_vector<bool> h_data   = unittest::random_integers<bool>(n);
+  thrust::device_vector<bool> d_data = h_data;
+
+  thrust::sort(h_data.begin(), h_data.end());
+  thrust::sort(d_data.begin(), d_data.end());
+
+  ASSERT_EQUAL(h_data, d_data);
+}
+DECLARE_UNITTEST(TestSortBool);
+
+void TestSortBoolDescending()
+{
+  const size_t n = 10027;
+
+  thrust::host_vector<bool> h_data   = unittest::random_integers<bool>(n);
+  thrust::device_vector<bool> d_data = h_data;
+
+  thrust::sort(h_data.begin(), h_data.end(), ::cuda::std::greater<bool>());
+  thrust::sort(d_data.begin(), d_data.end(), ::cuda::std::greater<bool>());
+
+  ASSERT_EQUAL(h_data, d_data);
+}
+DECLARE_UNITTEST(TestSortBoolDescending);
+
+// See also: https://github.com/NVIDIA/cccl/issues/4919
+void TestSortTrivial()
+{
+  thrust::host_vector<int> h_data = {1, 0, -1, -2, -3};
+  thrust::host_vector<int> ref    = {-3, -2, -1, 0, 1};
+
+  thrust::sort(h_data.begin(), h_data.end());
+  ASSERT_EQUAL(h_data, ref);
+}
+DECLARE_UNITTEST(TestSortTrivial);