OpenMP 奇偶换排序

▶ 使用 OpenMP 进行奇偶交换排序

● 代码

 #include <stdio.h>
 #include <stdlib.h>
 #include <omp.h>
 #include <time.h>

 const int thread = , dataSize = ;

 int main0(int argc, char* argv[])// 每次并行时即时产生多个线程
 {
     int i, j, threadReal, data[dataSize];
     clock_t time;
     if (argc >  && *argv[] > ''&& *argv[] < '')
         threadReal = atoi(argv[]);
     else
         threadReal = thread;
     srand();
     #pragma omp parallel for num_threads(thread)
     for (i = ; i < dataSize; i++)
         data[i] = rand();

     time = clock();
     for (i = ; i < dataSize; i++)
     {
         if (i % )
         {
             #pragma omp parallel for num_threads(thread) default(none) shared(data, dataSize) private(j)
             for (j = ; j < dataSize - ; j += )
             {
                 if (data[j + ] < data[j])
                     data[j + ] ^= data[j], data[j] ^= data[j + ], data[j + ] ^= data[j];
             }
         }
         else
         {
             #pragma omp parallel for num_threads(thread) default(none) shared(data, dataSize) private(j)
             for (j = ; j < dataSize; j += )
             {
                 if (data[j - ] > data[j])
                     data[j - ] ^= data[j], data[j] ^= data[j - ], data[j - ] ^= data[j];
             }
         }
     }
     time = clock() - time;
     printf("Sort finished!\n");
     for (i = ; i < dataSize - ; i++)
     {
         if (data[i] > data[i + ])
         {
             printf("Sort error at %d, data[i] = %d,data[i+1] = %d, time = %d ms\n", i, data[i], data[i + ], time);
             break;
         }
     }
     if (i == dataSize - )
         printf("Sort correct, time = %d ms\n", time);
     getchar();
     return ;
 }

 int main1(int argc, char* argv[])// 预先产生需要的线程
 {
     int i, j, threadReal, data[dataSize];
     clock_t time;
     if (argc >  && *argv[] > ''&& *argv[] < '')
         threadReal = atoi(argv[]);
     else
         threadReal = thread;
     srand();
     #pragma omp parallel for num_threads(thread)
     for (i = ; i < dataSize; i++)
         data[i] = rand();

     time = clock();
     #pragma omp parallel num_threads(thread) default(none) shared(data, dataSize) private(i, j) // 预先说明并行的参数，特别是规定使用的线程数
     for (i = ; i < dataSize; i++)                                                              // 注意这层没有 for 子句，且 i 也作为私有变量
     {
         if (i % )
         {
             #pragma omp for// 每次并行时使用预先规定的线程数和参数，使用完毕后保留，直到退出外层循环再销毁
             for (j = ; j < dataSize - ; j += )
             {
                 if (data[j + ] < data[j])
                     data[j + ] ^= data[j], data[j] ^= data[j + ], data[j + ] ^= data[j];
             }
         }
         else
         {
             #pragma omp for
             for (j = ; j < dataSize; j += )
             {
                 if (data[j - ] > data[j])
                     data[j - ] ^= data[j], data[j] ^= data[j - ], data[j - ] ^= data[j];
             }
         }
     }
     time = clock() - time;
     printf("Sort finished!\n");
     for (i = ; i < dataSize - ; i++)
     {
         if (data[i] > data[i + ])
         {
             printf("Sort error at %d, data[i] = %d,data[i+1] = %d, time = %d ms\n", i, data[i], data[i + ], time);
             break;
         }
     }
     if (i == dataSize - )
         printf("Sort correct, time = %d ms\n", time);
     getchar();
     return ;
 }

● 输出结果与对比

// 每次并行时即时产生多个线程，分别为 1 个线程和 8 个线程
Sort finished!
Sort correct, time =  ms
Sort finished!
Sort correct, time =  ms

// 预先产生需要的线程，分别为 1 个线程和 8 个线程
Sort finished!
Sort correct, time =  ms
Sort finished!
Sort correct, time =  ms