Pseudo-Huber loss gives Newton boosting a smooth alternative to Huber loss. It preserves Huber’s outlier-limiting behavior while remaining differentiable enough for second-derivative methods. section 7.3.1 section 7.3.2
Its behavior follows the residual size:
- For residuals close to zero, it behaves like squared error, producing 1/2·(y − f(x))². section 7.3.1
- For larger residuals, it approximates Huber loss, which transitions toward scaled absolute error and limits outlier influence. section 7.3.1
- Unlike Huber and absolute error losses, it supports Newton boosting because it is differentiable for second-derivative calculations. section 7.3.2 section 7.4.4
Using pseudo-Huber loss with XGBoost
Configure XGBRegressor with objective='reg:pseudohubererror', then tune tree depth, learning rate, feature sampling, and L1/L2 regularization through randomized cross-validation. In one regression comparison, the resulting model reached test MSE 0.0947 and test MAE 0.2244, close to LightGBM’s Huber result. section 7.3.2
