Function idx

src/backend/cuda/kernel/fast.hpp:32–34

inline __device__ int idx_x(const int i) { return idx_y((i + 4) & 15); }

inline __device__ int idx(const int x, const int y) {
    return ((threadIdx.x + 3 + x) + (blockDim.x + 6) * (threadIdx.y + 3 + y));
}

// test_greater()
// Tests if a pixel x > p + thr