Hello,

I’m CUDA newbie and I’m trying to implement image variance filter with CUDA. The problem that has occured to me is that “if” statement kind of does not work.

```
__global__ void __cudaVarianceFilter(cv::cuda::PtrStep<int> integralImg, cv::cuda::PtrStep<uint64_t > integralImg_squared,
int * windows_d, int * d_inWinIndices, int numInWins, float minVar)
{
int idx = blockDim.x * blockIdx.x + threadIdx.x;
if (idx < numInWins) {
int winIdx = d_inWinIndices[idx];
int * win = &windows_d[winIdx * TLD_WINDOW_SIZE];
int x1 = win[0] + 1;
int y1 = win[1] + 1;
int w = win[2];
int h = win[3];
int x2 = x1 + w - 1;
int y2 = y1 + h - 1;
float area = w * h;
uint64_t mX = __fdividef(integralImg(y2, x2) - integralImg(y1 - 1, x2) - integralImg(y2, x1 - 1) + integralImg(y1 - 1, x1 - 1), area);
uint64_t mX2 = __fdividef((integralImg_squared(y2, x2) - integralImg_squared(y1 - 1, x2) - integralImg_squared(y2, x1 - 1) + integralImg_squared(y1 - 1, x1 - 1)), area);
uint64_t variance = mX2 - __powf(mX, 2);
#if __CUDA_ARCH__ >= 200
if(idx%50==0)
printf("%d , minvar = %f \n", variance, minVar);
if(variance <minVar)
printf("The variance < minVar");
#endif
d_inWinIndices[idx] = (variance < minVar) ? -1 : d_inWinIndices[idx];
}
}
```

The problem is that the statement “if(variance < minVar)” is never true, and I do not know why, because I’ve even printf some of the values to see if maybe the calculations are wrong, but that is not the point. Here are some results of my code:

http://2.1m.yt/cFGO1f.png

Can you please point out my mistake?

Thanks a lot