How to use tbb::parallel_for & tbb::blocked_range2d

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C++

Hi all:
I don't know to use tbb::parall_for & tbb::backed_range2d ,if i have a four for loop.
for example:

void  Filter_Giws ( const Mat src,Mat &dst, const int win_size )
{
 int num_rows=0, num_cols=0;
 int half_win=0;
 int ir=0, ic=0;
 int iwr=0, iwc=0;
 int r_begin=0, r_end=0;/* vertical limits of the filtering operation */
 int c_begin=0, c_end=0;/* horizontal limits of the filtering operation */
 int wr_begin=0, wr_end=0;/* vertical limits of the filtering window */
 int wc_begin=0, wc_end=0;/* horizontal limits of the filtering window */
 int center_val=0;
 int cur_val=0;
 double weight=0;
 double weight_sum=0;
 double conv_sum=0;

 Mat dst2;
 Mat src2;

 CV_FUNCNAME("Filter_Giws");

 tbb::task_scheduler_init init;

 __CV_BEGIN__;
 CV_ASSERT(src.type()==CV_8UC1);

 half_win = win_size / 2;

 src2.create(cv::Size(src.rows+2*half_win,src.cols+2*half_win),CV_8UC1);
 copyMakeBorder(src,src2,half_win,half_win,half_win,half_win,BORDER_CONSTANT);

 num_rows = src2.rows;//get_num_rows ( in_img );
 num_cols =src2.cols;// get_num_cols ( in_img );

 dst.create(src.size(),src.type());

 /*
    Determine the limits of the filtering operation. Pixels
    in the output image outside these limits are set to 0.
  */
 r_begin = half_win;
 r_end = num_rows - half_win;
 c_begin = half_win;
 c_end = num_cols - half_win;

 /* Initialize the vertical limits of the filtering window */
 wr_begin = 0;
 wr_end = win_size;

 /* For each image row */

 tbb::parallel_for(tbb::blocked_range2d<int,int>(r_begin,r_end,c_begin,c_end),
   ParallelApplyGiwsFilter(src2,dst,win_size),tbb::auto_partitioner());

 init.terminate();
.......
}

&

class ParallelApplyGiwsFilter
{
public:
    ParallelApplyGiwsFilter(Mat  imgin,Mat& imgout,int win_size) : _imgin(imgin),_imgout(imgout),_win_size(win_size) {}
    void operator() (const tbb::blocked_range2d<int,int>& r) const
    {
        int wc_begin=0;
        int center_val=0;
        int cur_val=0;
        double weight=0;
        double weight_sum=0;
        double conv_sum=0;
        int wr_begin = 0;
        int wr_end = _win_size;
        int wc_end=0;
        int iwr=0;
        int iwc=0;

        for(size_t i=r.rows().begin(); i!=r.rows().end(); ++i)
        {
            /* Initialize the horizontal limits of the filtering window */
            wc_begin = 0;
            wc_end = _win_size;

            /* For each image column */
            for ( size_t j=r.cols().begin(); j!=r.cols().end(); ++j )
            {
                center_val = _imgin.at<uchar>(i,j);
                conv_sum = 0.0;
                weight_sum = 0.0;

                for ( iwr = wr_begin; iwr < wr_end; iwr++ )
                {
                    for ( iwc = wc_begin; iwc < wc_end; iwc++ )
                    {
                        cur_val =_imgin.at<uchar>(iwr,iwc) ;

                        /* Determine the weight for the current pixel */
                        if ( cur_val == center_val )
                        {
                            weight = 2.0;
                        }
                        else
                        {
                            weight = 1.0 / std::abs ( cur_val - center_val );
                        }
                        conv_sum += weight * cur_val;
                        weight_sum += weight;
                    }
                }
                _imgout.at<uchar>(i-2,j-2)=saturate_cast<uchar>(conv_sum/weight_sum);
                /* Update the horizontal limits of the filtering window */
                wc_begin++;
                wc_end++;
            }

            /* Update the vertical limits of the filtering window */
            wr_begin++;
            wr_end++;
        }
    }
private:
    Mat _imgin,&_imgout;
    int _win_size;
};

Is it right???