Function Nudge

tensorflow/core/kernels/fake_quant_ops_functor.h:41–61

Gymnastics with nudged zero point is to ensure that real zero maps to an integer, which is required for e.g. zero-padding in convolutional layers. Outputs nudged_min, nudged_max, nudged_scale.

// an integer, which is required for e.g. zero-padding in convolutional layers.
// Outputs nudged_min, nudged_max, nudged_scale.
EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE void Nudge(
    const float min, const float max, const int quant_min, const int quant_max,
    float* nudged_min, float* nudged_max, float* scale) {
  const float quant_min_float = static_cast<float>(quant_min);
  const float quant_max_float = static_cast<float>(quant_max);
  *scale = (max - min) / (quant_max_float - quant_min_float);
  const float zero_point_from_min = quant_min_float - min / *scale;
  const uint16 nudged_zero_point = [zero_point_from_min, quant_min,
                                    quant_min_float, quant_max,
                                    quant_max_float] {
    if (zero_point_from_min < quant_min_float) {
      return static_cast<uint16>(quant_min);
    }
    if (zero_point_from_min > quant_max_float) {
      return static_cast<uint16>(quant_max);
    }
    return static_cast<uint16>(StdRound(zero_point_from_min));
  }();
  *nudged_min = (quant_min_float - nudged_zero_point) * (*scale);
  *nudged_max = (quant_max_float - nudged_zero_point) * (*scale);
}

template <typename T>
using ConstScalar = typename tensorflow::TTypes<T>::ConstScalar;