__global__ void gpuKernel
(
  BYTE *src,float *aux, /* source, destination */
  size_t memPitch, /* memory pitch */
  size_t memPitchAux,
  int w,int h, /* size of picture  */
  BYTE *Rng,int sizeRng, /* ranges */
  BYTE *Dir,int sizeDir /* directions */
)
{
  int rx = ((VEC2*)Rng)->x; // range of calculations (sizeXofwindow = 2*rx+1)
  int ry = ((VEC2*)Rng)->y; // range of calculations (sizeYofwindow = 2*ry+1)

  int i = blockIdx.x * blockDim.x + threadIdx.x; // x-coordinate of pixel = column in devmem
  int j = blockIdx.y * blockDim.y + threadIdx.y; // y-coordinate of pixel = row in devmem
  int idx  = j * memPitchAux/sizeof(float) + i;

  int i0 = i-rx, i1 = i+rx; // the range of calculation for columns
  int j0 = j-ry, j1 = j+ry; // the range of calculation for rows

  float g=0.0f ,g0=0.0f;

 if((i0>=0) && (i1< w) && (j0>=0) && (j1< h))
 {
    g = 0.0;

  for(int n=0; n<5; n++)
    {
     for(int js=jsB; js<swy-jsE; js++)
      {
    for(int is=isB; is<swx-isE; is++)
    {
      int ic = (int) fabsf(src[(j0+js)*memPitch+i0+is]-
                               src[(j0+js+jsD)*memPitch+i0+is+isD]);
      c[ic] += 1.0f;
    }
      }

        g = fmaxf(g,g0*s);
     }

    aux[idx] = g;
    __syncthreads();
 }
 else
 {
  aux[idx] = 0;
 }
}

int main()
{
[..]
   checkCudaErrors(cudaMemcpy2D(data->BufGPU[0],data->memPitch, /* to GPU (device) */
        data->BufCPU[0],data->imgPitch, /* from CPU (host) */
        data->imgWidth, data->imgHeight, /* size of data (image) */
        cudaMemcpyHostToDevice));
  cudaThreadSynchronize();

[..]
  dim3 dimBlock(data->dimBLX,data->dimBLY,1);
  dim3 dimGrid(data->memPitch/dimBlock.x ,data->imgHeight/dimBlock.y,1);

  size_t memPitch = data->memPitch;

  float *auxD;
  size_t auxDPitch;
  size_t auxHPitch;
  checkCudaErrors(cudaMallocPitch((void**)&auxD,&auxDPitch,w*sizeof(float),h));

  auxHPitch = w*sizeof(float);
  float *auxH = (float *) malloc(h*auxHPitch);

  gpuKernel<<<dimGrid,dimBlock>>> (data->BufGPU[0],auxD,
                           memPitch,auxDPitch,w, h,
                           Rng,sRng,
                           Dir,sDir);
  cudaThreadSynchronize();

  checkCudaErrors(cudaMemcpy2D(auxH,auxHPitch,  // to CPU (host)
               auxD,auxDPitch,  // from GPU (device)
           auxHPitch, h, // size of data (image)
               cudaMemcpyDeviceToHost));

  cudaThreadSynchronize();
[..]
}