Writing Benchmarks in C++

// Define the function under test
static void BM_StringCopy(benchmark::State &state) {
  std::string x = "hello";

  // Google benchmark relies on state.begin() and state.end() to run the benchmark and count iterations
  for (auto _ : state) {
    std::string copy(x);

    // Use DoNotOptimize and ClobberMemory to prevent the compiler optimizing away your benchmark
    // See: https://google.github.io/benchmark/user_guide.html#preventing-optimization
    benchmark::DoNotOptimize(copy);
    benchmark::ClobberMemory();
  }
}
// Register the benchmarked to be called by the executable
BENCHMARK(BM_StringCopy);

static void BM_memcpy(benchmark::State &state) {
  char *src = new char[state.range(0)];
  char *dst = new char[state.range(0)];
  memset(src, 'x', state.range(0));
  for (auto _ : state) {
    memcpy(dst, src, state.range(0));
    benchmark::DoNotOptimize(dst);
    benchmark::ClobberMemory();
  }
  delete[] src;
  delete[] dst;
}

BENCHMARK(BM_memcpy)->Range(8, 8 << 10);

// Entrypoint of the benchmark executable
BENCHMARK_MAIN();

cmake_minimum_required(VERSION 3.12)
include(FetchContent)

project(my_codspeed_project VERSION 0.0.0 LANGUAGES CXX)

# Enable release mode with debug symbols to display useful profiling data
set(CMAKE_BUILD_TYPE RelWithDebInfo)

set(BENCHMARK_DOWNLOAD_DEPENDENCIES ON)

FetchContent_Declare(
    google_benchmark
    GIT_REPOSITORY https://github.com/CodSpeedHQ/codspeed-cpp # Target the codspeed cpp repository
    SOURCE_SUBDIR google_benchmark # Make sure to target the google_benchmark subdirectory
    GIT_TAG main # Or chose a specific version or git ref, check the releases page on the repository
)

FetchContent_MakeAvailable(google_benchmark)

# Declare your benchmark executable and its sources here
add_executable(my_benchmark_executable benches/bench.cpp)

# Link your executable against the `benchmark::benchmark`, the `google_benchmark` library
# Note: the first argument must match the first argument of the `add_executable` call
target_link_libraries(my_benchmark_executable benchmark::benchmark)

name: CodSpeed Benchmarks

on:
  push:
    branches:
      - "main" # or "master"
  pull_request:
  # `workflow_dispatch` allows CodSpeed to trigger backtest
  # performance analysis in order to generate initial data.
  workflow_dispatch:

jobs:
  benchmarks:
    name: Run benchmarks
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Build the benchmark target(s)
        run: |
          mkdir build
          cd build
          cmake -DCODSPEED_MODE=instrumentation ..
          make -j
      - name: Run the benchmarks
        uses: CodSpeedHQ/action@v4
        with:
          mode: instrumentation
          run: ./build/my_benchmark_executable  # Replace with the proper executable path
          token: ${{ secrets.CODSPEED_TOKEN }} # optional for public repos

# Create individual benchmark executables
set(BENCHMARKS first_bench second_bench third_bench)

# Add `bench_name` target with `bench_name.cpp` source for each bench listed above
foreach(benchmark IN LISTS BENCHMARKS)
  add_executable(${benchmark} benches/${benchmark}.cpp)
  target_link_libraries(${benchmark}
    benchmark::benchmark
  )
endforeach()

# Create a custom target to run all benchmarks locally
add_custom_target(run_all_benchmarks
  COMMAND ${CMAKE_COMMAND} -E echo "Running all benchmarks..."
)
# Register each benchmark target as a dependency of
foreach(benchmark IN LISTS BENCHMARKS)
  add_custom_command(
    TARGET run_all_benchmarks
    POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E echo "Running ${benchmark}..."
    COMMAND $<TARGET_FILE:${benchmark}>
    WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
  )
endforeach()

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "codspeed_cpp", # Name the codspeed_cpp will be imported as

    # Target the main branch automatically, or select a specific version
    urls = ["https://github.com/CodSpeedHQ/codspeed-cpp/archive/refs/heads/main.zip"],
    strip_prefix = "codspeed-cpp-main",
)

cc_binary(
    name = "my_benchmark", # Name of your benchmark target
    srcs = glob(["*.cpp", "*.hpp"]), # Or define sources however you wish
    deps = [
        "@codspeed_cpp//google_benchmark:benchmark", # codspeed_cpp must match the name you imported the lib in WORKSPACE
    ],
)

name: CodSpeed Benchmarks

on:
  push:
    branches:
      - "main" # or "master"
  pull_request:
  # `workflow_dispatch` allows CodSpeed to trigger backtest
  # performance analysis in order to generate initial data.
  workflow_dispatch:

jobs:
  benchmarks:
    name: Run benchmarks
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Set up Bazel
        uses: bazelbuild/setup-bazelisk@v2
      - name: Build the benchmark target
        run: |
          bazel build //path/to/bench:my_benchmark --@codspeed_cpp//core:codspeed_mode=instrumentation
      - name: Run the benchmarks
        uses: CodSpeedHQ/action@v4
        with:
          mode: instrumentation
          run: |
            bazel run //path/to/bench:my_benchmark --@codspeed_cpp//core:codspeed_mode=instrumentation
          token: ${{ secrets.CODSPEED_TOKEN }} # optional for public repos