可这code进行优化？ [英] Can this code be optimised?

问题描述

我有一些图像处理code来遍历2多维字节数组（大小相同）。它从源数组的值，再对其进行计算，然后将结果存储在另一个数组。

  INT xSize = ResultImageData.GetLength（0）;
INT ySize = ResultImageData.GetLength（1）;

为（中间体X = 0 X  - 其中; xSize; X ++）
{
   对于（INT Y = 0; Y＆LT; ySize; Y ++）
   {
      ResultImageData [X，Y] =（字节）（（CurrentImageData [X，Y] * AlphaValue）+
                                    （AlphaImageData [X，Y] * OneMinusAlphaValue））;
   }
}
 

环路目前需要11毫秒〜，我认为主要是由于访问字节数组值作为计算pretty的简单（2乘法和加法1）。

有什么我可以做，以加快这？这是我的程序的时间关键部分，这code被称为每秒80-100次，所以任何速度上涨，但是小会有所作为。此外，在时刻xSize = 768和ySize = 576，但这样会在将来增加

更新：感谢 Guffa （见回答以下），以下$ C $ Ç为我节省了每个循环4-5ms。虽然它的不安全的code。

  INT大小= ResultImageData.Length;
INT计数器= 0;
不安全
{
    固定（BYTE * R = ResultImageData，C = CurrentImageData，A = AlphaImageData）
    {
        而（尺寸大于0）
        {
            *（R +计数器）=（字节）（*（C +计数器）* AlphaValue +
                                    *（A +计数器）* OneMinusAlphaValue）;
            反++;
            尺寸 - ;
        }
    }
}
 

解决方案

要得到任何真正的speadup此code，你就需要使用指针访问数组时，要删除所有指标的计算和边界检查。

  INT大小= ResultImageData.Length;
不安全
{
   固定（BYTE * RP = ResultImageData，CP = CurrentImageData，AP = AlphaImageData）
   {
      字节* R = RP;
      字节* C = CP;
      字节* A = AP;
      而（尺寸大于0）
      {
         * R =（字节）（* C * AlphaValue + * A * OneMinusAlphaValue）;
          -  [R ++;
         C ++;
         A ++;
         尺寸 - ;
      }
   }
}
 

编辑：
固定变量不能改变，所以我加了code的指针复制到可以改变的新指针。

I have some image processing code that loops through 2 multi-dimensional byte arrays (of the same size). It takes a value from the source array, performs a calculation on it and then stores the result in another array.

int xSize = ResultImageData.GetLength(0);
int ySize = ResultImageData.GetLength(1);

for (int x = 0; x < xSize; x++)
{                
   for (int y = 0; y < ySize; y++) 
   {                                                
      ResultImageData[x, y] = (byte)((CurrentImageData[x, y] * AlphaValue) +
                                    (AlphaImageData[x, y] * OneMinusAlphaValue));
   }
}

The loop currently takes ~11ms, which I assume is mostly due to accessing the byte arrays values as the calculation is pretty simple (2 multiplications and 1 addition).

Is there anything I can do to speed this up? It is a time critical part of my program and this code gets called 80-100 times per second, so any speed gains, however small will make a difference. Also at the moment xSize = 768 and ySize = 576, but this will increase in the future.

Update: Thanks to Guffa (see answer below), the following code saves me 4-5ms per loop. Although it is unsafe code.

int size = ResultImageData.Length;
int counter = 0;
unsafe
{
    fixed (byte* r = ResultImageData, c = CurrentImageData, a = AlphaImageData)
    {
        while (size > 0)
        {
            *(r + counter) = (byte)(*(c + counter) * AlphaValue + 
                                    *(a + counter) * OneMinusAlphaValue);
            counter++;
            size--;
        }
    }
}

解决方案

To get any real speadup for this code you would need to use pointers to access the arrays, that removes all the index calculations and bounds checking.

int size = ResultImageData.Length;
unsafe 
{
   fixed(byte* rp = ResultImageData, cp = CurrentImageData, ap = AlphaImageData) 
   {
      byte* r = rp;
      byte* c = cp;
      byte* a = ap;
      while (size > 0) 
      {
         *r = (byte)(*c * AlphaValue + *a * OneMinusAlphaValue);
         r++;
         c++;
         a++;
         size--;
      }
   }
}

Edit:
Fixed variables can't be changed, so I added code to copy the pointers to new pointers that can be changed.

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