[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/trivial_sequence.cu

@@ -0,0 +1,47 @@
+#include <thrust/detail/trivial_sequence.h>
+#include <thrust/iterator/zip_iterator.h>
+#include <thrust/type_traits/is_contiguous_iterator.h>
+
+#include <unittest/unittest.h>
+
+template <typename Iterator>
+void test(Iterator first, Iterator last)
+{
+  using System = typename thrust::iterator_system<Iterator>::type;
+  System system;
+  thrust::detail::trivial_sequence<Iterator, System> ts(system, first, last);
+  using ValueType = typename ::cuda::std::iterator_traits<Iterator>::value_type;
+
+  ASSERT_EQUAL_QUIET((ValueType) ts.begin()[0], ValueType(0, 11));
+  ASSERT_EQUAL_QUIET((ValueType) ts.begin()[1], ValueType(2, 11));
+  ASSERT_EQUAL_QUIET((ValueType) ts.begin()[2], ValueType(1, 13));
+  ASSERT_EQUAL_QUIET((ValueType) ts.begin()[3], ValueType(0, 10));
+  ASSERT_EQUAL_QUIET((ValueType) ts.begin()[4], ValueType(1, 12));
+
+  ts.begin()[0] = ValueType(0, 0);
+  ts.begin()[1] = ValueType(0, 0);
+  ts.begin()[2] = ValueType(0, 0);
+  ts.begin()[3] = ValueType(0, 0);
+  ts.begin()[4] = ValueType(0, 0);
+
+  using TrivialIterator = typename thrust::detail::trivial_sequence<Iterator, System>::iterator_type;
+
+  ASSERT_EQUAL(thrust::is_contiguous_iterator_v<Iterator>, false);
+  ASSERT_EQUAL(thrust::is_contiguous_iterator_v<TrivialIterator>, true);
+}
+
+template <class Vector>
+void TestTrivialSequence()
+{
+  Vector A{0, 2, 1, 0, 1};
+  Vector B{11, 11, 13, 10, 12};
+
+  test(thrust::make_zip_iterator(A.begin(), B.begin()), thrust::make_zip_iterator(A.end(), B.end()));
+
+  Vector refA{0, 2, 1, 0, 1};
+  ASSERT_EQUAL(A, refA);
+  // ensure that values weren't modified
+  Vector refB{11, 11, 13, 10, 12};
+  ASSERT_EQUAL(B, refB);
+}
+DECLARE_VECTOR_UNITTEST(TestTrivialSequence);