[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/cuda/swap_ranges.cu

@@ -0,0 +1,64 @@
+#include <thrust/execution_policy.h>
+#include <thrust/swap.h>
+
+#include <unittest/unittest.h>
+
+#ifdef THRUST_TEST_DEVICE_SIDE
+template <typename ExecutionPolicy, typename Iterator1, typename Iterator2>
+__global__ void swap_ranges_kernel(ExecutionPolicy exec, Iterator1 first1, Iterator1 last1, Iterator2 first2)
+{
+  thrust::swap_ranges(exec, first1, last1, first2);
+}
+
+template <typename ExecutionPolicy>
+void TestSwapRangesDevice(ExecutionPolicy exec)
+{
+  using Vector = thrust::device_vector<int>;
+
+  Vector v1{0, 1, 2, 3, 4};
+  Vector v2{5, 6, 7, 8, 9};
+  Vector v1_ref(v2);
+  Vector v2_ref(v1);
+
+  swap_ranges_kernel<<<1, 1>>>(exec, v1.begin(), v1.end(), v2.begin());
+  cudaError_t const err = cudaDeviceSynchronize();
+  ASSERT_EQUAL(cudaSuccess, err);
+
+  ASSERT_EQUAL(v1, v1_ref);
+  ASSERT_EQUAL(v2, v2_ref);
+}
+
+void TestSwapRangesDeviceSeq()
+{
+  TestSwapRangesDevice(thrust::seq);
+}
+DECLARE_UNITTEST(TestSwapRangesDeviceSeq);
+
+void TestSwapRangesDeviceDevice()
+{
+  TestSwapRangesDevice(thrust::device);
+}
+DECLARE_UNITTEST(TestSwapRangesDeviceDevice);
+#endif
+
+void TestSwapRangesCudaStreams()
+{
+  using Vector = thrust::device_vector<int>;
+
+  Vector v1{0, 1, 2, 3, 4};
+  Vector v2{5, 6, 7, 8, 9};
+  Vector v1_ref(v2);
+  Vector v2_ref(v1);
+
+  cudaStream_t s;
+  cudaStreamCreate(&s);
+
+  thrust::swap_ranges(thrust::cuda::par.on(s), v1.begin(), v1.end(), v2.begin());
+  cudaStreamSynchronize(s);
+
+  ASSERT_EQUAL(v1, v1_ref);
+  ASSERT_EQUAL(v2, v2_ref);
+
+  cudaStreamDestroy(s);
+}
+DECLARE_UNITTEST(TestSwapRangesCudaStreams);