Calibrating group rewards can avoid failures from independent KL penalties

ZCPO uses each response’s relative policy drift to adjust zero-sum reward coefficients within a sampled group.

Chinese Tech
Fei Ding

Alibaba Group

Research Digest··3 min read
Ding examines why reference-policy KL regularization, which discourages a trained model from drifting too far from a baseline, can impair group-relative policy optimization.

The author analyzes group-relative policy optimization, a reinforcement-learning approach that compares rewards among several responses to the same input without training a separate value model.

Why this paper

From Alibaba Group

In one line

ZCPO uses conditional-KL drift to calibrate zero-sum group-relative rewards, avoiding seven failure modes that can make independent reference-policy KL regularization harmful.

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