Gradient-based one-side sampling (GOSS) speeds gradient boosting by keeping examples with large gradient magnitudes and sampling examples with small gradients. Large gradients indicate predictions that still need substantial improvement, while small-gradient examples are already better trained. Unlike random downsampling, GOSS preserves difficult examples without letting them dominate the learner. section 5.3.1
GOSS proceeds as a targeted reduction of the training set:
- Compute each training example’s gradient magnitude from the current boosting iteration. section 5.3.1
- Retain examples with the largest gradients because they offer the strongest immediate learning signal. section 5.3.1
- Sample a fraction of small-gradient examples so correctly classified cases remain represented. section 5.3.1
- Reweight the sampled small-gradient examples to compensate for their reduced representation, then continue tree learning on the resulting subset. section 5.3.1
Large-scale document retrieval
A LightGBM document-retrieval model can use GOSS when the training set is large. It reduces the number of training examples and is typically fast to train, although downsampling may reduce generalization compared with standard gradient-boosted decision trees. section 5.5.2
GOSS is one of LightGBM’s scaling mechanisms, complementing histogram-based tree learning and exclusive feature bundling: it reduces examples, while EFB reduces features. section 5.3 section 5.3.1

