project_6/cccl_upstream/libcudacxx/benchmarks/bench/transform/babelstream.cu

//===----------------------------------------------------------------------===//
//
// Part of libcu++, the C++ Standard Library for your entire system,
// 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) 2026 NVIDIA CORPORATION & AFFILIATES.
//
//===----------------------------------------------------------------------===//

#include <thrust/device_vector.h>
#include <thrust/execution_policy.h>
#include <thrust/iterator/zip_iterator.h>

#include <cuda/functional>
#include <cuda/iterator>
#include <cuda/memory_pool>
#include <cuda/std/execution>
#include <cuda/stream>

#include <nvbench_helper.cuh>

// The benchmarks are inspired by the BabelStream thrust version:
// https://github.com/UoB-HPC/BabelStream/blob/main/src/thrust/ThrustStream.cu

// Modified from BabelStream to also work for integers
constexpr auto startA      = 1; // BabelStream: 0.1
constexpr auto startB      = 2; // BabelStream: 0.2
constexpr auto startC      = 3; // BabelStream: 0.1
constexpr auto startScalar = 4; // BabelStream: 0.4

using element_types = nvbench::type_list<std::int8_t, std::int16_t, float, double, __int128>;
// Different benchmarks use a different number of buffers. H200/B200 can fit 2^31 elements for all benchmarks and types.
// Upstream BabelStream uses 2^25. Allocation failure just skips the benchmark
auto array_size_powers = std::vector<std::int64_t>{25, 31};

template <typename T>
static void mul(nvbench::state& state, nvbench::type_list<T>)
{
  const auto n = static_cast<std::size_t>(state.get_int64("Elements"));
  thrust::device_vector<T> b(n, startB);
  thrust::device_vector<T> c(n, startC);

  state.add_element_count(n);
  state.add_global_memory_reads<T>(n);
  state.add_global_memory_writes<T>(n);

  caching_allocator_t alloc{};

  const T scalar = startScalar;
  state.exec(nvbench::exec_tag::gpu | nvbench::exec_tag::no_batch | nvbench::exec_tag::sync,
             [&](nvbench::launch& launch) {
               do_not_optimize(cuda::std::transform(
                 cuda_policy(alloc, launch), c.begin(), c.end(), b.begin(), [=] _CCCL_HOST_DEVICE(const T& ci) {
                   return ci * scalar;
                 }));
             });
}

NVBENCH_BENCH_TYPES(mul, NVBENCH_TYPE_AXES(element_types))
  .set_name("mul")
  .set_type_axes_names({"T{ct}"})
  .add_int64_power_of_two_axis("Elements", array_size_powers);

template <typename T>
static void add(nvbench::state& state, nvbench::type_list<T>)
{
  const auto n = static_cast<std::size_t>(state.get_int64("Elements"));
  thrust::device_vector<T> a(n, startA);
  thrust::device_vector<T> b(n, startB);
  thrust::device_vector<T> c(n, startC);

  state.add_element_count(n);
  state.add_global_memory_reads<T>(2 * n);
  state.add_global_memory_writes<T>(n);

  caching_allocator_t alloc{};

  state.exec(nvbench::exec_tag::gpu | nvbench::exec_tag::no_batch | nvbench::exec_tag::sync,
             [&](nvbench::launch& launch) {
               do_not_optimize(cuda::std::transform(
                 cuda_policy(alloc, launch), a.begin(), a.end(), b.begin(), c.begin(), cuda::std::plus<T>{}));
             });
}

NVBENCH_BENCH_TYPES(add, NVBENCH_TYPE_AXES(element_types))
  .set_name("add")
  .set_type_axes_names({"T{ct}"})
  .add_int64_power_of_two_axis("Elements", array_size_powers);

template <typename T>
static void triad(nvbench::state& state, nvbench::type_list<T>)
{
  const auto n = static_cast<std::size_t>(state.get_int64("Elements"));
  thrust::device_vector<T> a(n, startA);
  thrust::device_vector<T> b(n, startB);
  thrust::device_vector<T> c(n, startC);

  state.add_element_count(n);
  state.add_global_memory_reads<T>(2 * n);
  state.add_global_memory_writes<T>(n);

  caching_allocator_t alloc{};

  const T scalar = startScalar;
  state.exec(nvbench::exec_tag::gpu | nvbench::exec_tag::no_batch | nvbench::exec_tag::sync,
             [&](nvbench::launch& launch) {
               do_not_optimize(cuda::std::transform(
                 cuda_policy(alloc, launch),
                 b.begin(),
                 b.end(),
                 c.begin(),
                 a.begin(),
                 [=] _CCCL_HOST_DEVICE(const T& bi, const T& ci) {
                   return bi + scalar * ci;
                 }));
             });
}

NVBENCH_BENCH_TYPES(triad, NVBENCH_TYPE_AXES(element_types))
  .set_name("triad")
  .set_type_axes_names({"T{ct}"})
  .add_int64_power_of_two_axis("Elements", array_size_powers);

template <typename T>
static void nstream(nvbench::state& state, nvbench::type_list<T>)
{
  const auto n = static_cast<std::size_t>(state.get_int64("Elements"));
  thrust::device_vector<T> a(n, startA);
  thrust::device_vector<T> b(n, startB);
  thrust::device_vector<T> c(n, startC);

  state.add_element_count(n);
  state.add_global_memory_reads<T>(3 * n);
  state.add_global_memory_writes<T>(n);

  caching_allocator_t alloc{};

  const T scalar = startScalar;
  state.exec(nvbench::exec_tag::gpu | nvbench::exec_tag::no_batch | nvbench::exec_tag::sync,
             [&](nvbench::launch& launch) {
               do_not_optimize(cuda::std::transform(
                 cuda_policy(alloc, launch),
                 cuda::make_zip_iterator(a.begin(), b.begin(), c.begin()),
                 cuda::make_zip_iterator(a.end(), b.end(), c.end()),
                 a.begin(),
                 cuda::zip_function{[=] _CCCL_HOST_DEVICE(const T& ai, const T& bi, const T& ci) {
                   return ai + bi + scalar * ci;
                 }}));
             });
}

NVBENCH_BENCH_TYPES(nstream, NVBENCH_TYPE_AXES(element_types))
  .set_name("nstream")
  .set_type_axes_names({"T{ct}"})
  .add_int64_power_of_two_axis("Elements", array_size_powers);