想问一下，多核CPU与SMP架构的高性能计算机有什么编程上的类似或者不同之处？具体要注意哪些区别？

[Hutcher]

如题，谢谢！

[Hutcher]

int find_steady_state (int p, int id, int my_rows, double **u, double **w)
{
   double     diff;             /* 当前进程最大温差 */
   double     global_diff;      /* 全局最大温差 */
   int        i, j;
   int        its;              /* 迭代次数 */
   MPI_Status status;           
   double     tdiff;            /* 当前线程最大温差 */

   its = 0;
   for (;;) {

	  /* 交换辅助网格点上的近似解 */
      if (id > 0)
         MPI_Send (u[1], N, MPI_DOUBLE, id-1, 0, MPI_COMM_WORLD);
      if (id < p-1) {
         MPI_Send (u[my_rows-2], N, MPI_DOUBLE, id+1, 0, MPI_COMM_WORLD);
         MPI_Recv (u[my_rows-1], N, MPI_DOUBLE, id+1, 0, MPI_COMM_WORLD,
            &status);
      }
      if (id > 0)
         MPI_Recv (u[0], N, MPI_DOUBLE, id-1, 0, MPI_COMM_WORLD, &status);

	  /* 更新求得的数值解 */
      diff = 0.0;
#pragma omp parallel private (i, j, tdiff)
{
      tdiff = 0.0;
#pragma omp for
      for (i = 1; i < my_rows-1; i++)
         for (j = 1; j < N-1; j++) {
            w[i][j] = (u[i-1][j] + u[i+1][j] +
                       u[i][j-1] + u[i][j+1])/4.0;
            if (fabs(w[i][j] - u[i][j]) > tdiff)
               tdiff = fabs(w[i][j] - u[i][j]);
         }
#pragma omp for nowait
      for (i = 1; i < my_rows-1; i++)
         for (j = 1; j < N-1; j++)
            u[i][j] = w[i][j];
#pragma omp critical
      if (tdiff > diff) diff = tdiff;
}
      MPI_Allreduce (&diff, &global_diff, 1, MPI_DOUBLE, MPI_MAX,
         MPI_COMM_WORLD);

	  /* 中止条件 */
      if (global_diff <= EPSILON) break;
      its++;
   }
   return its;
}