背景
老實說，C++11中對非同步的支援不必Python和JavaScript弱。
實現（程式碼）
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#include <iostream> #include <vector> #include <algorithm> #include <future> template <typename RAIter> int parallel_sum(RAIter front, RAIter beg, RAIter end) { auto len = end - beg; if (len < 1000) { char out[50]; sprintf(out, "Calculate from %d to %d\n", beg - front, end - front); std::cout << out; return std::accumulate(beg, end, 0); } RAIter mid = beg + len / 2; auto handle_right = std::async(std::launch::async, parallel_sum<RAIter>, front, mid, end); auto handle_left = std::async(std::launch::async, parallel_sum<RAIter>, front, beg, mid); return handle_left.get() + handle_right.get(); } int main() { std::vector<int> v(20000, 1); std::cout << "The sum is " << parallel_sum(v.begin(), v.begin(), v.end()) << '\n'; } |
輸出
可能一
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Calculate from 8125 to 8750 Calculate from 18125 to 18750 Calculate from 10625 to 11250 Calculate from 2500 to 3125 Calculate from 13750 to 14375 Calculate from 5000 to 5625 Calculate from 1250 to 1875 Calculate from 3750 to 4375 Calculate from 16250 to 16875 Calculate from 17500 to 18125 Calculate from 10000 to 10625 Calculate from 625 to 1250 Calculate from 18750 to 19375 Calculate from 15625 to 16250 Calculate from 3125 to 3750 Calculate from 12500 to 13125 The sum is 20000 |
可能二
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Calculate from 1875 to 2500 Calculate from 3750 to 4375 Calculate from 8750 to 9375 Calculate from 7500 to 8125 Calculate from 15000 to 15625 Calculate from 10000 to 10625 Calculate from 1250 to 1875 Calculate from 6875 to 7500 Calculate from 0 to 625 Calculate from 3125 to 3750 Calculate from 5625 to 6250 Calculate from 5000 to 5625 Calculate from 6250 to 6875 Calculate from 2500 to 3125 The sum is 20000 |
可能….
…..
注意
如果在輸出中間資訊的時候不先現在字串裡輸出會很亂，因為同一行cout輸出不同項的操作不是原子的，中間可能會轉到其他執行緒去。