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Kto To
Asked:2020-02-17 16:40:44 +0000 UTC2020-02-17 16:40:44 +0000 UTC

一个简单的多线程示例

  • 772

帮助实现示例程序。我做得对还是有更简单的方法？好吧，我的程序挂在了线上auto r = f.get(); ，当其中一个线程找到密钥时，如何让线程完成它们的工作？这是一个示例任务。它能在我的电脑上运行 3 年这一事实并不重要。

#include <iostream>
#include <future>
#include <vector>

#define KEY_PASS  (0xFFAAFFAABBCCDDEE)

bool checkPass(uint64_t pass) {
    return pass == KEY_PASS;
}

const uint64_t STEP = 0x1000000000000000;

uint64_t funcAsync(uint64_t begin) {
    for (uint64_t i = 0; i < STEP; ++i) {
        if (checkPass(begin + i)) {
            return i;
        }
    }
    return uint64_t(-1);
}


int main() {
// Пример без работы с потоками
//    for (uint64_t i = 0; i < UINT64_MAX; ++i) {
//        if (checkPass(i)) {
//            std::cout << std::hex << i << std::endl;
//            break;
//        }
//    }
// Пример с потоками
    uint64_t i = 0;
    std::vector<std::future<uint64_t>> v;
    do {
        v.push_back(std::async(std::launch::async, funcAsync, i));
        i += STEP;
        std::cout << (i >> 60) << " open threads" << std::endl;
    } while (i != 0);
    for (auto& f: v) {
        auto r = f.get();
        if (r != uint64_t(-1)) {
            std::cout << std::hex << r << std::endl;
            break;
        }
    }
}
c++

1 个回答

  1. Best Answer
    // $ g++ -std=c++11 -Wall -Wpedantic -Wextra -pthread futur.cpp -o futur
#include <iostream>
#include <future>
#include <vector>

#define KEY_PASS  (0xFFAAFFAABBCCDDEE)

bool checkPass(uint64_t pass) {
  return  (random() & 0xff) == 0 ;
    //return pass == KEY_PASS;
}

const uint64_t STEP = 0x1000000000000000;

volatile std ::  atomic  < bool  > flag_stop{ false };

struct s_result {
  bool  valid ;
  uint64_t value ;
} ;

s_result funcAsync(uint64_t begin) {
    for (uint64_t i = 0; i < STEP; ++i) {
        if ( flag_stop ) s_result{false,uint64_t(-1)};
        if (checkPass(begin+i)) {
            flag_stop = true ;
            return s_result{true,begin + i};
        }
    }
    return s_result{false,uint64_t(-1)};
}


int main() {
// Пример без работы с потоками
//    for (uint64_t i = 0; i < UINT64_MAX; ++i) {
//        if (checkPass(i)) {
//            std::cout << std::hex << i << std::endl;
//            break;
//        }
//    }
// Пример с потоками
  srandom(time(nullptr));
    uint64_t i = 0;
    std::vector<std::future<s_result>> v;
    do {
        v.push_back(std::async(std::launch::async, funcAsync, i));
        i += STEP;
        std::cout << (i >> 60) << " open threads" << std::endl;
    } while (i != 0);
    for (auto& f: v) {
        auto r = f.get();
        if ( r.valid ) {
          std::cout << "found " << std::hex << r.value << std::endl;
          break;
        }

    }
}
    • 1

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