omp最大减少量与索引存储量 [英] omp max reduction with storage of index

问题描述

使用c ++ openmp 3.1，我实现了一个max reduce，它存储对象向量的整数变量(分数)的最大值.但我也想存储矢量索引，以使分数最高的对象获得访问. 我当前不成功的实现如下所示:

Using c++ openmp 3.1 I implemented a max reduction which stores the maximum value of integer variable (score) of an vector of objects (s). But I also want to store the vector index to acces the (s) object with the maximum score. My current unsuccesfull implementation looks like this:

//s is a vector of sol objects which contain apart from other variables an  integer     score    variable s[].score            
int bestscore = 0;
int bestant = 0;                
#pragma omp parallel shared(bestant)
{//start parallel session
    #pragma omp for    nowait reduction(max : bestscore)
    for (int ant = 0; ant<maxsols; ++ant) // for all ants
    {
        //procedures on s[ant] object which update the  int s[ant].score
        if (s[ant].score > bestscore)
        {
            //find the object with the highest score
            bestscore = s[ant].score;
            bestant = ant;//i also want know which ant has the highest score
        }
    }
}

代码会编译并运行.找到了最大的最高分，但Bestant获得了一个随机索引.链接到完成速度最快的线程的蚂蚁将存储在bestant中. bestscore以0开头，因此在大多数情况下s [ant] .score会获得更高的分数，并且bestscore和bestant也会更新. 我认为我需要一个简化运算符来处理诸如更新最佳分数"之类的防腐剂.

The code compiles and runs. the maximum bestscore is found but bestant gets a random index. The ant linked to the fastest thread to finish gets stored in bestant. bestscore start with a value of 0 so in most cases s[ant].score will have a higher score and bestscore and bestant are updated. I think I need a reduction operator for bestant like "on update of bestscore".

推荐答案

尝试一下

int bestscore = 0;
int bestant = 0;
#pragma omp parallel
{
    int bestscore_private = 0;
    int bestant_private = 0;
    #pragma omp for nowait
    for (int ant = 0; ant<maxsols; ++ant) {         
        if (s[ant].score > bestscore_private) {
            bestscore_private = s[ant].score;
            bestant_private = ant;
        }
    }
    #pragma omp critical 
    {
        if(bestscore_private>bestscore) {
            bestscore = bestscore_private;
            bestant = besant_private;
        }
    }
}

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