[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/is_partitioned.cu

@@ -0,0 +1,135 @@
+#include <thrust/execution_policy.h>
+#include <thrust/functional.h>
+#include <thrust/partition.h>
+
+#include <unittest/unittest.h>
+
+#ifdef THRUST_TEST_DEVICE_SIDE
+template <typename ExecutionPolicy, typename Iterator, typename Predicate, typename Iterator2>
+__global__ void
+is_partitioned_kernel(ExecutionPolicy exec, Iterator first, Iterator last, Predicate pred, Iterator2 result)
+{
+  *result = thrust::is_partitioned(exec, first, last, pred);
+}
+
+template <typename T>
+struct is_even
+{
+  _CCCL_HOST_DEVICE bool operator()(T x) const
+  {
+    return ((int) x % 2) == 0;
+  }
+};
+
+template <typename ExecutionPolicy>
+void TestIsPartitionedDevice(ExecutionPolicy exec)
+{
+  size_t n = 1000;
+
+  n = ::cuda::std::max<size_t>(n, 2);
+
+  thrust::device_vector<int> v = unittest::random_integers<int>(n);
+
+  thrust::device_vector<bool> result(1);
+
+  v[0] = 1;
+  v[1] = 0;
+
+  is_partitioned_kernel<<<1, 1>>>(exec, v.begin(), v.end(), is_even<int>(), result.begin());
+  {
+    cudaError_t const err = cudaDeviceSynchronize();
+    ASSERT_EQUAL(cudaSuccess, err);
+  }
+
+  ASSERT_EQUAL(false, result[0]);
+
+  thrust::partition(v.begin(), v.end(), is_even<int>());
+
+  is_partitioned_kernel<<<1, 1>>>(exec, v.begin(), v.end(), is_even<int>(), result.begin());
+  {
+    cudaError_t const err = cudaDeviceSynchronize();
+    ASSERT_EQUAL(cudaSuccess, err);
+  }
+
+  ASSERT_EQUAL(true, result[0]);
+}
+
+void TestIsPartitionedDeviceSeq()
+{
+  TestIsPartitionedDevice(thrust::seq);
+}
+DECLARE_UNITTEST(TestIsPartitionedDeviceSeq);
+
+void TestIsPartitionedDeviceDevice()
+{
+  TestIsPartitionedDevice(thrust::device);
+}
+DECLARE_UNITTEST(TestIsPartitionedDeviceDevice);
+#endif
+
+void TestIsPartitionedCudaStreams()
+{
+  thrust::device_vector<int> v(4);
+  v[0] = 1;
+  v[1] = 1;
+  v[2] = 1;
+  v[3] = 0;
+
+  cudaStream_t s;
+  cudaStreamCreate(&s);
+
+  // empty partition
+  ASSERT_EQUAL_QUIET(true,
+                     thrust::is_partitioned(thrust::cuda::par.on(s), v.begin(), v.begin(), ::cuda::std::identity{}));
+
+  // one element true partition
+  ASSERT_EQUAL_QUIET(
+    true, thrust::is_partitioned(thrust::cuda::par.on(s), v.begin(), v.begin() + 1, ::cuda::std::identity{}));
+
+  // just true partition
+  ASSERT_EQUAL_QUIET(
+    true, thrust::is_partitioned(thrust::cuda::par.on(s), v.begin(), v.begin() + 2, ::cuda::std::identity{}));
+
+  // both true & false partitions
+  ASSERT_EQUAL_QUIET(true,
+                     thrust::is_partitioned(thrust::cuda::par.on(s), v.begin(), v.end(), ::cuda::std::identity{}));
+
+  // one element false partition
+  ASSERT_EQUAL_QUIET(true,
+                     thrust::is_partitioned(thrust::cuda::par.on(s), v.begin() + 3, v.end(), ::cuda::std::identity{}));
+
+  v[0] = 1;
+  v[1] = 0;
+  v[2] = 1;
+  v[3] = 1;
+
+  // not partitioned
+  ASSERT_EQUAL_QUIET(false,
+                     thrust::is_partitioned(thrust::cuda::par.on(s), v.begin(), v.end(), ::cuda::std::identity{}));
+
+  cudaStreamDestroy(s);
+}
+DECLARE_UNITTEST(TestIsPartitionedCudaStreams);
+
+template <typename T>
+struct is_even_non_const
+{
+  _CCCL_HOST_DEVICE bool operator()(T x) // no const
+  {
+    return ((int) x % 2) == 0;
+  }
+};
+
+void TestIsPartitionedWithNonConstPredicate()
+{
+  thrust::device_vector<int> partitioned   = {0, 2, 4, 1, 3, 5};
+  thrust::device_vector<int> unpartitioned = {0, 1, 2, 3};
+
+  ASSERT_EQUAL_QUIET(
+    true, thrust::is_partitioned(thrust::cuda::par, partitioned.begin(), partitioned.end(), is_even_non_const<int>{}));
+
+  ASSERT_EQUAL_QUIET(
+    false,
+    thrust::is_partitioned(thrust::cuda::par, unpartitioned.begin(), unpartitioned.end(), is_even_non_const<int>{}));
+}
+DECLARE_UNITTEST(TestIsPartitionedWithNonConstPredicate);