基于OpenMP的C++并行编程简单示例

示例要求：在整数A和B之间找到符合条件的值X，使f(X)=C。

示例代码（需要在VS中开启OpenMP支持）：

 #include<iostream>
 #include<time.h>
 #include"omp.h"

 int f(int i) {
     int i4_huge = ;
     int j;
     int k;
     int value;
     value = i;
     for (j = ; j <= ; j++)
     {
         k = value / ;
         value =  * (value - k * ) - k * ;
         if (value <= )
         {
             value = value + i4_huge;
         }
     }
     return value;
 }

 int search(int a, int b, int c)
 {
     int fi;
     int i;
     int j;

     j = -;

     #pragma omp parallel for num_threads(6)
     for (i = a; i <= b; i++)
     {
         fi = f(i);
         if (fi == c)
         {
             j = i;
             break;
         }
     }

     return j;
 }

 int main()
 {
     int j;
     int a = ;
     int b = ;
     int c = ;
     double wtime;

     clock_t start, finish;
     double totaltime;
     start = clock();

     j = search(a, b, c);

     finish = clock();
     totaltime = (double)(finish - start) / CLOCKS_PER_SEC;
     std::cout << "\n search运行时间为" << totaltime << "秒！" << std::endl;
     system("pause");
     return ;
 }

并行算法的加速情况：

加速前：

加速后：