问openmp并行性能

EN

map <int, map< int, double> > dist;   //construct the distance matrix 

int c=count(dat.at(0).begin(),dat.at(0).end(),delm)+1;

#pragma omp parallel for shared (c,dist)

for(int p=0;p<dat.size();p++)
{

    for(int j=p+1;j<dat.size();j++)
    {
        double ecl=0;

        string line1=dat.at(p);
        string line2=dat.at(j);

        for (int i=0;i<c;i++)
        {

            double num1=atof(line1.substr(0,line1.find_first_of(delm)).c_str());

            line1=line1.substr(line1.find_first_of(delm)+1).c_str();

            double num2=atof(line2.substr(0,line2.find_first_of(delm)).c_str());

            line2=line2.substr(line2.find_first_of(delm)+1).c_str();

            ecl += (num1-num2)*(num1-num2);
        }

        ecl=sqrt(ecl);

#pragma omp critical
        {
            dist[p][j]=ecl;
            dist[j][p]=ecl;
        }
    }
}