How to benchmark C++ function performance?

To benchmark a C function, you can take the following steps: Use a timing tool (such as the std::chrono library) to measure the execution time. Write a benchmark function that executes code and returns the execution time. Leverage the benchmark library for advanced features such as statistics collection and comparison.

How to benchmark C function performance

Benchmarking is an important technique for measuring code performance and comparing different implementations . In C, we can benchmark function performance through the following methods:

1. Using timing tools

C providesstd::chrono Library containing classes for measuring time. We can use std::chrono::high_resolution_clock to obtain high-precision timing:

#include <chrono>

using namespace std::chrono;

auto start = high_resolution_clock::now();
// 待测试代码
auto end = high_resolution_clock::now();

2. Write a benchmark function

Write a function to Execute the code to be tested and return the execution time:

#include <chrono>

using namespace std::chrono;

double benchmark(int n) {
  auto start = high_resolution_clock::now();
  // 待测试代码
  auto end = high_resolution_clock::now();
  return duration_cast<duration<double>>(end - start).count();
}

3. Using a benchmark library

There are also various C benchmark libraries available that provide more Advanced features such as statistics collection and comparison. Here are some popular libraries:

• [benchmark](https://github.com/google/benchmark)
• [boost::benchmark](https://www .boost.org/doc/libs/1_65_1/libs/benchmark/doc/html/index.html)
• [google-benchmark](https://github.com/google/benchmark)
• [Catch2](https://github.com/catchorg/Catch2)

Practical case:

Suppose we want to benchmark a search Functionfind_element():

#include <chrono>
#include <vector>

using namespace std::chrono;

double find_element_benchmark(size_t n) {
  // 生成一个包含 n 个元素的数组
  std::vector<int> arr(n, 0);
  
  // 查找一个不存在的元素
  auto start = high_resolution_clock::now();
  auto pos = std::find(arr.begin(), arr.end(), -1);
  auto end = high_resolution_clock::now();
  if (pos != arr.end()) return -1;  // 仅在元素找到时返回 -1

  return duration_cast<duration<double>>(end - start).count();
}

int main() {
  // 多次测试不同数组大小
  for (size_t n = 1000; n <= 1000000; n *= 10) {
    // 运行基准测试
    double time = find_element_benchmark(n);
    
    // 打印结果
    std::cout << "数组大小: " << n << "\t执行时间: " << time << " 秒" << std::endl;
  }

  return 0;
}

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