Question

我已经编辑了这个问题（希望）让问题更加清晰。以下函数包含两个相同代码的块。每个块产生的输出是不同的。具体而言，在执行第一个临界区时，“done”变量未正确更新。关键部分确实具有保持输出不混合的效果。第二个代码块似乎产生预期的输出。产生的输出遵循代码。

有没有人对此行为有任何解释。我开始怀疑微软的一个错误。我正在使用Visual Studio 2010 Premium SP1进行开发。

感谢您提供的任何见解。

void OmpTest(int iterations)
{
  int done;
  // . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
  done = 0;
  #pragma omp parallel for
  for (int ii = 0; ii < iterations; ++ii)
  {
    // do something useful
    cv::Mat frame(32, 32, CV_8UC1, cv::Scalar(255));

    // now update
    #pragma omp critical
    {
      ++done;
      cout << setw(3) << 100 * done / iterations << "%  " 
            << setw(3) << done << " of " << setw(3) << iterations 
            << "   ii = " << ii << endl;
    }
  }
  cout << endl;

  // . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
  done = 0;
  #pragma omp parallel for
  for (int ii = 0; ii < iterations; ++ii)
  {
    // do something useful
    cv::Mat frame(32, 32, CV_8UC1, cv::Scalar(255));

    // now update
    #pragma omp critical
    {
      ++done;
      cout << setw(3) << 100 * done / iterations << "%  " 
            << setw(3) << done << " of " << setw(3) << iterations 
            << "   ii = " << ii << endl;
    }
  }
  cout << endl;
}

输出：

% OmpTest
  6%    1 of  16   ii = 0
 12%    2 of  16   ii = 1
  6%    1 of  16   ii = 8
  6%    1 of  16   ii = 6
  6%    1 of  16   ii = 12
  6%    1 of  16   ii = 2
  6%    1 of  16   ii = 4
  6%    1 of  16   ii = 14
 12%    2 of  16   ii = 15
 12%    2 of  16   ii = 9
 12%    2 of  16   ii = 7
 12%    2 of  16   ii = 13
 12%    2 of  16   ii = 3
 12%    2 of  16   ii = 5
  6%    1 of  16   ii = 10
 12%    2 of  16   ii = 11

  6%    1 of  16   ii = 10
 12%    2 of  16   ii = 2
 18%    3 of  16   ii = 3
 25%    4 of  16   ii = 14
 31%    5 of  16   ii = 15
 37%    6 of  16   ii = 12
 43%    7 of  16   ii = 8
 50%    8 of  16   ii = 4
 56%    9 of  16   ii = 11
 62%   10 of  16   ii = 6
 68%   11 of  16   ii = 0
 75%   12 of  16   ii = 13
 81%   13 of  16   ii = 9
 87%   14 of  16   ii = 5
 93%   15 of  16   ii = 7
100%   16 of  16   ii = 1

当并行部分创建cv :: Mat时，Omp的行为不同

0 个答案: