fixed bug in SURF_GPU (compute descriptors, tid < 25)

modules/gpu/src/cuda/surf.cu

@@ -831,6 +831,8 @@ namespace cv { namespace gpu { namespace surf
 
         const int tid = threadIdx.y * blockDim.x + threadIdx.x;
 
+        if (tid < 25)
+        {
             sdxabs[tid] = fabs(sdx[tid]); // |dx| array
             sdyabs[tid] = fabs(sdy[tid]); // |dy| array
             __syncthreads();
@@ -849,6 +851,7 @@ namespace cv { namespace gpu { namespace surf
                 descriptors_block[3] = sdyabs[0];
             }
         }
+    }
 
 	__global__ void compute_descriptors128(PtrStepf descriptors, const float* featureX, const float* featureY, const float* featureSize, const float* featureDir)
     {
@@ -867,6 +870,8 @@ namespace cv { namespace gpu { namespace surf
 
         const int tid = threadIdx.y * blockDim.x + threadIdx.x;
 
+        if (tid < 25)
+        {
             if (sdy[tid] >= 0)
             {
                 sd1[tid] = sdx[tid];
@@ -926,6 +931,7 @@ namespace cv { namespace gpu { namespace surf
                 descriptors_block[7] = sdabs2[0];
             }
         }
+    }
 
     template <int BLOCK_DIM_X> __global__ void normalize_descriptors(PtrStepf descriptors)
     {