Empirical Reward Model Loss Formula using Bradley-Terry Model
The reward model is trained by minimizing an empirical loss function derived from the Bradley-Terry model for pairwise comparisons. The objective is to adjust the model's parameters, , to minimize the negative log-likelihood of the observed human preferences in the dataset . This is achieved by applying the sigmoid function to the difference in reward scores for the preferred response, , and the rejected response, , and then minimizing the negative logarithm of this probability, averaged over the entire dataset. The formula is:

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Ch.4 Alignment - Foundations of Large Language Models
Foundations of Large Language Models
Foundations of Large Language Models Course
Computing Sciences
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Empirical Reward Model Loss Formula using Bradley-Terry Model
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