OMP中的减少和折叠子句有一些混淆点 [英] Reduction and collapse clauses in OMP have some confusing points

问题描述

OMP中的缩减和折叠子句都让我感到困惑，
一些提示突然出现在我脑海中。

Both of reduction and collapse clauses in OMP confuses me, some points raised popped into my head

1. 用负号工作？如所列的限制此处


2. 是有任何工作要实现减号？


3. 一元运算符如何工作，即x ++或x--？是 - 或++应用于每个部分结果？或者只有在创建全局结果时才一次？这两种情况完全不同。

关于崩溃..
我们可以在嵌套循环上应用collapse，
之间的代码例如

About the collapse.. could we apply collapse on a nested loops but have some lines of code in between for example

for (int i = 0; i < 4; i++)
{
    cout << "Hi"; //This is an extra line. which breaks the 2 loops.
    for (int j = 0; j < 100; j++)
    {
        cout << "*";
    }
}

推荐答案

1 &对于减号，你减去什么？如果你有两个线程，你做 result_thread_1 - result_thread_2 或 result_thread_2 - result_thread_1 吗？如果你有两个以上的线程，那么它会更加混乱：我只有一个否定词，所有其他都是正数？只有一个积极的词，而其他的是负的？是混合吗？哪些结果是哪些？

1 & 2. For minus, what are you subtracting from? If you have two threads, do you do result_thread_1 - result_thread_2, or result_thread_2 - result_thread_1? If you have more than 2 threads, then it gets even more confusing: Do I only have one negative term and all others are positive? Is there only one positive term and others are negative? Is it a mix? Which results are which? As such, no, there is no workaround.

1. 如果 x ++ 或 x - ，假设它们在缩减循环内，它们应该出现在每个部分结果中。

1. In the event of x++ or x--, assuming that they are within the reduction loop, they should happen to each partial result.

是的，我相信这样。

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