[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/examples/cudax/CMakeLists.txt

@@ -0,0 +1,75 @@
+# SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+cmake_minimum_required(VERSION 3.18 FATAL_ERROR)
+
+project(CUDAX_SAMPLES CUDA CXX)
+
+# This example uses the CMake Package Manager (CPM) to simplify fetching CCCL from GitHub
+# For more information, see https://github.com/cpm-cmake/CPM.cmake
+include(cmake/CPM.cmake)
+
+# We define these as variables so they can be overridden in CI to pull from a PR instead of CCCL `main`
+# In your project, these variables are unnecessary and you can just use the values directly
+set(
+  CCCL_REPOSITORY
+  "https://github.com/NVIDIA/cccl"
+  CACHE STRING
+  "Git repository to fetch CCCL from"
+)
+set(CCCL_TAG "main" CACHE STRING "Git tag/branch to fetch from CCCL repository")
+
+# This will automatically clone CCCL from GitHub and make the exported cmake targets available
+CPMAddPackage(
+  NAME CCCL
+  GIT_REPOSITORY "${CCCL_REPOSITORY}"
+  GIT_TAG ${CCCL_TAG}
+  GIT_SHALLOW ON
+  # The following is required to make the `CCCL::cudax` target available:
+  OPTIONS "CCCL_ENABLE_UNSTABLE ON"
+)
+
+# Default to building for the GPU on the current system
+if (NOT DEFINED CMAKE_CUDA_ARCHITECTURES)
+  set(CMAKE_CUDA_ARCHITECTURES native)
+endif()
+
+add_library(cudax_samples_interface INTERFACE)
+
+target_link_libraries(cudax_samples_interface INTERFACE CCCL::CCCL CCCL::cudax)
+
+if ("MSVC" STREQUAL "${CMAKE_CXX_COMPILER_ID}")
+  # mdspan on windows only works in C++20 mode
+  target_compile_features(cudax_samples_interface INTERFACE cxx_std_20)
+
+  if (MSVC_TOOLSET_VERSION LESS 143)
+    # winbase.h(9572): warning C5105: macro expansion producing 'defined' has undefined behavior
+    target_compile_options(
+      cudax_samples_interface
+      INTERFACE
+        $<$<COMPILE_LANGUAGE:CXX>:/wd5105>
+        $<$<COMPILE_LANG_AND_ID:CUDA,NVIDIA>:-Xcompiler=/wd5105>
+    )
+  endif()
+endif()
+
+# The vector_add sample demonstrates a simple CUDA kernel that adds two vectors
+add_executable(vector_add vector_add/vector_add.cu)
+target_link_libraries(vector_add PUBLIC cudax_samples_interface)
+
+# This is only relevant for internal testing and not needed by end users.
+include(CTest)
+enable_testing()
+add_test(NAME vector_add COMMAND vector_add)

cccl_upstream/examples/cudax/README.md

@@ -0,0 +1,5 @@
+
+# Overview
+
+This example extends the `example_project` by additionally enabling the CUDA Experimental library, `cudax`.
+See the `example_project`'s README for additional information.

cccl_upstream/examples/cudax/vector_add/vector.cuh

@@ -0,0 +1,145 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of CUDA Experimental in CUDA C++ Core Libraries,
+// under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+// SPDX-FileCopyrightText: Copyright (c) 2024 NVIDIA CORPORATION & AFFILIATES.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _CUDAX__CONTAINER_VECTOR
+#define _CUDAX__CONTAINER_VECTOR
+
+#include <cuda/__cccl_config>
+
+#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
+#  pragma GCC system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
+#  pragma clang system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
+#  pragma system_header
+#endif // no system header
+
+#include <thrust/device_vector.h>
+#include <thrust/host_vector.h>
+
+#include <cuda/std/__type_traits/maybe_const.h>
+#include <cuda/std/span>
+#include <cuda/stream>
+
+#include <cuda/experimental/__detail/utility.cuh>
+#include <cuda/experimental/__launch/param_kind.cuh>
+
+namespace cuda::experimental
+{
+using ::cuda::std::span;
+using ::thrust::device_vector;
+using ::thrust::host_vector;
+
+template <typename _Ty>
+class vector
+{
+public:
+  vector() = default;
+  explicit vector(size_t __n)
+      : __h_(__n)
+  {}
+
+  _Ty& operator[](size_t __i) noexcept
+  {
+    __dirty_ = true;
+    return __h_[__i];
+  }
+
+  const _Ty& operator[](size_t __i) const noexcept
+  {
+    return __h_[__i];
+  }
+
+private:
+  void sync_host_to_device([[maybe_unused]] ::cuda::stream_ref __str, __detail::__param_kind __p) const
+  {
+    if (__dirty_)
+    {
+      if (__p == __detail::__param_kind::_out)
+      {
+        // There's no need to copy the data from host to device if the data is
+        // only going to be written to. We can just allocate the device memory.
+        __d_.resize(__h_.size());
+      }
+      else
+      {
+        // TODO: use a memcpy async here
+        __d_ = __h_;
+      }
+      __dirty_ = false;
+    }
+  }
+
+  void sync_device_to_host(::cuda::stream_ref __str, __detail::__param_kind __p) const
+  {
+    if (__p != __detail::__param_kind::_in)
+    {
+      // TODO: use a memcpy async here
+      __str.sync(); // wait for the kernel to finish executing
+      __h_ = __d_;
+    }
+  }
+
+  template <__detail::__param_kind _Kind>
+  class __action //: private __detail::__immovable
+  {
+    using __cv_vector = ::cuda::std::__maybe_const<_Kind == __detail::__param_kind::_in, vector>;
+
+  public:
+    explicit __action(::cuda::stream_ref __str, __cv_vector& __v) noexcept
+        : __str_(__str)
+        , __v_(__v)
+    {
+      __v_.sync_host_to_device(__str_, _Kind);
+    }
+
+    __action(__action&&) = delete;
+
+    ~__action()
+    {
+      __v_.sync_device_to_host(__str_, _Kind);
+    }
+
+    ::cuda::std::span<_Ty> transformed_argument()
+    {
+      return {__v_.__d_.data().get(), __v_.__d_.size()};
+    }
+
+  private:
+    ::cuda::stream_ref __str_;
+    __cv_vector& __v_;
+  };
+
+  [[nodiscard]] friend __action<__detail::__param_kind::_inout>
+  transform_launch_argument(::cuda::stream_ref __str, vector& __v) noexcept
+  {
+    return __action<__detail::__param_kind::_inout>{__str, __v};
+  }
+
+  [[nodiscard]] friend __action<__detail::__param_kind::_in>
+  transform_launch_argument(::cuda::stream_ref __str, const vector& __v) noexcept
+  {
+    return __action<__detail::__param_kind::_in>{__str, __v};
+  }
+
+  template <__detail::__param_kind _Kind>
+  [[nodiscard]] friend __action<_Kind>
+  transform_launch_argument(::cuda::stream_ref __str, __detail::__box<vector, _Kind> __b) noexcept
+  {
+    return __action<_Kind>{__str, __b.__val};
+  }
+
+  mutable host_vector<_Ty> __h_;
+  mutable device_vector<_Ty> __d_{};
+  mutable bool __dirty_ = true;
+};
+} // namespace cuda::experimental
+
+#endif

cccl_upstream/examples/cudax/vector_add/vector_add.cu

@@ -0,0 +1,127 @@
+/* Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *  * Neither the name of NVIDIA CORPORATION nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * Vector addition: C = A + B.
+ *
+ * This sample is a very basic sample that implements element by element
+ * vector addition. It is the same as the sample illustrating Chapter 2
+ * of the programming guide with some additions like error checking.
+ */
+
+#include <stdio.h>
+
+// For the CUDA runtime routines (prefixed with "cuda_")
+#include <cuda/std/span>
+
+#include <cuda/experimental/launch.cuh>
+#include <cuda/experimental/stream.cuh>
+
+#include <cuda_runtime.h>
+
+#include "vector.cuh"
+
+namespace cudax = cuda::experimental;
+using cudax::in;
+using cudax::out;
+
+/**
+ * CUDA Kernel Device code
+ *
+ * Computes the vector addition of A and B into C. The 3 vectors have the same
+ * number of elements numElements.
+ */
+__global__ void vectorAdd(cudax::span<const float> A, cudax::span<const float> B, cudax::span<float> C)
+{
+  int i = blockDim.x * blockIdx.x + threadIdx.x;
+
+  if (i < A.size())
+  {
+    C[i] = A[i] + B[i] + 0.0f;
+  }
+}
+
+/**
+ * Host main routine
+ */
+int main(void)
+try
+{
+  // A CUDA stream on which to execute the vector addition kernel
+  cudax::stream stream(cuda::devices[0]);
+
+  // Print the vector length to be used, and compute its size
+  int numElements = 50000;
+  printf("[Vector addition of %d elements]\n", numElements);
+
+  // Allocate the host vectors
+  cudax::vector<float> A(numElements); // input
+  cudax::vector<float> B(numElements); // input
+  cudax::vector<float> C(numElements); // output
+
+  // Initialize the host input vectors
+  for (int i = 0; i < numElements; ++i)
+  {
+    A[i] = rand() / (float) RAND_MAX;
+    B[i] = rand() / (float) RAND_MAX;
+  }
+
+  // Define the kernel launch parameters
+  constexpr int threadsPerBlock = 256;
+  auto config                   = cuda::distribute<threadsPerBlock>(numElements);
+
+  // Launch the vectorAdd kernel
+  printf("CUDA kernel launch with %zu blocks of %d threads\n", cuda::block.count(cuda::grid, config), threadsPerBlock);
+  cudax::launch(stream, config, vectorAdd, in(A), in(B), out(C));
+
+  printf("waiting for the stream to finish\n");
+  stream.sync();
+
+  printf("verifying the results\n");
+  // Verify that the result vector is correct
+  for (int i = 0; i < numElements; ++i)
+  {
+    if (fabs(A[i] + B[i] - C[i]) > 1e-5)
+    {
+      fprintf(stderr, "Result verification failed at element %d!\n", i);
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  printf("Test PASSED\n");
+
+  printf("Done\n");
+  return 0;
+}
+catch (const std::exception& e)
+{
+  printf("caught an exception: \"%s\"\n", e.what());
+}
+catch (...)
+{
+  printf("caught an unknown exception\n");
+}