Openmp简单例子

/* * Compile: * g++ a.cpp -fopenmp * * 速度明显提升一倍(双核) */ #include <iostream> using namespace std; static long long num_rects = 1000000000; int main(int args, char** argv){ double mid, height, width, sum = 0.0; int i; double area; width = 1.0/(double)num_rects; #pragma omp parallel for private(mid, height) reduction(+:sum) for(i=0; i<num_rects; i++){ mid = (i+0.5)*width; height = 4.0/(1.0+mid*mid); sum += height; } area = width * sum; cout << "The value of PI is " << area << endl; return 0; }