openmp 并行计算

luoganttcc_son

于 2022-07-31 09:48:09 发布

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分类专栏： c++ 文章标签： c++ 开发语言

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这篇博客介绍了如何利用OpenMP在C++中实现并行计算。通过example.cpp的代码示例和CMakeLists.txt的配置，展示了如何构建并运行一个OpenMP并行程序。

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代码在git

example.cpp

#include <iostream>
#include <omp.h>
#include <string>

int main(int argc, char *argv[]) {
  std::cout << "number of available processors: " << omp_get_num_procs()
            << std::endl;
  std::cout << "number of threads: " << omp_get_max_threads() << std::endl;

  auto n = std::stol(argv[1]);
  std::cout << "we will form sum of numbers from 1 to " << n << std::endl;

  // start timer
  auto t0 = omp_get_wtime();

  auto s = 0LL;
#pragma omp parallel for reduction(+ : s)
  for (auto i = 1; i <= n; i++) {
    s += i;
  }

  // stop timer
  auto t1 = omp_get_wtime();

  std::cout << "sum: " << s << std::endl;
  std::cout << "elapsed wall clock time: " << t1 - t0 << " seconds" << std::endl;

  return 0;
}

CMakeLists.txt

# set minimum cmake version
cmake_minimum_required(VERSION 3.9 FATAL_ERROR)

# project name and language
project(recipe-05 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_EXTENSIONS OFF)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(OpenMP REQUIRED)

add_executable(example example.cpp)

target_link_libraries(example
  PUBLIC
    OpenMP::OpenMP_CXX
  )