严重的性能差异:调试与发布

Question

我有一个简单的算法,将拜耳图像通道(BGGR,RGGB,GBRG,GRBG)转换为rgb(去马赛克,但没有邻居).在我的实现中,我预先设置了偏移向量,这有助于我将拜耳通道索引转换为相应的rgb通道索引.唯一的问题是我在使用MSVC11的调试模式下获得了可怕的性能.在发布时,对于3264X2540大小的输入,该功能在~60ms内完成.对于调试中的相同输入,该函数在~20,000ms内完成.这超过了X300的差异,因为一些开发人员在调试中运行我的应用程序,这是不可接受的.

我的代码:

void ConvertBayerToRgbImageDemosaic(int* BayerChannel, int* RgbChannel, int Width, int 

Height, ColorSpace ColorSpace)
{
    int rgbOffsets[4]; //translates color location in Bayer block to it's location in RGB block. So R->0, G->1, B->2
    std::vector<int> bayerToRgbOffsets[4]; //the offsets from every color in the Bayer block to (bayer) indices it will be copied to (R,B are copied to all indices, Gr to R and Gb to B).
    //calculate offsets according to color space
    switch (ColorSpace)
    {
    case ColorSpace::BGGR:
            /*
             B G
             G R
            */ 
        rgbOffsets[0] = 2; //B->0
        rgbOffsets[1] = 1; //G->1
        rgbOffsets[2] = 1; //G->1
        rgbOffsets[3] = 0; //R->0
        //B is copied to every pixel in it's block
        bayerToRgbOffsets[0].push_back(0);
        bayerToRgbOffsets[0].push_back(1);
        bayerToRgbOffsets[0].push_back(Width);
        bayerToRgbOffsets[0].push_back(Width + 1);
        //Gb is copied to it's neighbouring B
        bayerToRgbOffsets[1].push_back(-1);
        bayerToRgbOffsets[1].push_back(0);
        //GR is copied to it's neighbouring R
        bayerToRgbOffsets[2].push_back(0);
        bayerToRgbOffsets[2].push_back(1);
        //R is copied to every pixel in it's block
        bayerToRgbOffsets[3].push_back(-Width - 1);
        bayerToRgbOffsets[3].push_back(-Width);
        bayerToRgbOffsets[3].push_back(-1);
        bayerToRgbOffsets[3].push_back(0);
        break;
    ... other color spaces
    }

    for (auto row = 0; row < Height; row++)
    {
        for (auto col = 0, bayerIndex = row * Width; col < Width; col++, bayerIndex++)
        {
            auto colorIndex = (row%2)*2 + (col%2); //0...3, For example in BGGR: 0->B, 1->Gb, 2->Gr, 3->R
            //iteration over bayerToRgbOffsets is O(1) since it is either sized 2 or 4.
            std::for_each(bayerToRgbOffsets[colorIndex].begin(), bayerToRgbOffsets[colorIndex].end(), 
                [&](int colorOffset)
                {
                    auto rgbIndex = (bayerIndex + colorOffset) * 3 + rgbOffsets[offset];
                    RgbChannel[rgbIndex] = BayerChannel[bayerIndex];
                });
        }
    }
}

我尝试过的:我尝试使用优化(/ O2)进行调试构建,但没有显着差异.我尝试用for_each一个普通的旧for循环替换内部语句,但无济于事.我有一个非常相似的算法,它将拜耳转换为"绿色"rgb(不将数据复制到块中的相邻像素),其中我没有使用它,std::vector并且调试和发布之间存在预期的运行时差异(X2-X3) ).那么std::vector问题可能就是这样吗？如果是这样,我该如何克服它？

Answer 1

在使用时std::vector,它将有助于禁用迭代器调试.

MSDN显示了如何做到这一点.

简单来说,#define在包含任何STL标头之前进行此操作:

#define _HAS_ITERATOR_DEBUGGING 0

根据我的经验,这给出了一个重要的调试版本的性能提升,虽然当然你失去一些调试功能.