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  #include <cub/device/device_histogram.cuh>
  
  using namespace cub;
  
  template <int NUM_CHANNELS,
            int ACTIVE_CHANNELS,
            int NUM_BINS,
            typename PixelType>
  double run_cub_histogram(
      PixelType *d_image,
      int width,
      int height,
      unsigned int *d_hist, 
      bool is_warmup)
  {
      constexpr bool is_float = std::is_same<PixelType, float4>::value;
  
      using SampleT = cub::detail::conditional_t<is_float, float, unsigned char>;   // Sample type
      using LevelT = cub::detail::conditional_t<is_float, float, unsigned int>;     // Level type (uint32 for uchar)
  
      // Setup data structures
      unsigned int*       d_histogram[ACTIVE_CHANNELS];
      int                 num_levels[ACTIVE_CHANNELS];            ///< [in] The number of boundaries (levels) for delineating histogram samples in each active channel.  Implies that the number of bins for channel<sub><em>i</em></sub> is <tt>num_levels[i]</tt> - 1.
      LevelT              lower_level[ACTIVE_CHANNELS];           ///< [in] The lower sample value bound (inclusive) for the lowest histogram bin in each active channel.
      LevelT              upper_level[ACTIVE_CHANNELS];           ///< [in] The upper sample value bound (exclusive) for the highest histogram bin in each active channel.
  
      for (int CHANNEL = 0; CHANNEL < ACTIVE_CHANNELS; ++CHANNEL)
      {
          d_histogram[CHANNEL] = d_hist + (CHANNEL * NUM_BINS);
          num_levels[CHANNEL] = NUM_BINS + 1;
          lower_level[CHANNEL] = 0;
          upper_level[CHANNEL] = (is_float) ? 1 : 256;
      }
  
      // Allocate temporary storage
      size_t temp_storage_bytes = 0;
      void *d_temp_storage = NULL;
  
      SampleT* d_image_samples = (SampleT*) d_image;
  
      // Get amount of temporary storage needed
      DeviceHistogram::MultiHistogramEven<NUM_CHANNELS, ACTIVE_CHANNELS>(
          d_temp_storage,
          temp_storage_bytes,
          d_image_samples,
          d_histogram,
          num_levels,
          lower_level,
          upper_level,
          width * height, 
          (cudaStream_t) 0,
          is_warmup);
  
      cudaMalloc(&d_temp_storage, temp_storage_bytes);
  
      GpuTimer gpu_timer;
      gpu_timer.Start();
  
      // Compute histogram
      DeviceHistogram::MultiHistogramEven<NUM_CHANNELS, ACTIVE_CHANNELS>(
          d_temp_storage,
          temp_storage_bytes,
          d_image_samples,
          d_histogram,
          num_levels,
          lower_level,
          upper_level,
          width * height, 
          (cudaStream_t) 0,
          is_warmup);
  
      gpu_timer.Stop();
      float elapsed_millis = gpu_timer.ElapsedMillis();
  
      cudaFree(d_temp_storage);
  
      return elapsed_millis;
  }
  
  