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