Reward Model Loss as Negative Log-Likelihood
To train the reward model in RLHF, the objective is to maximize the preference probability defined by the Bradley-Terry model. This is mathematically achieved by minimizing a loss function based on the negative log-likelihood over the human preference dataset . The loss function is given by: , where represents the trainable parameters of the reward model, and each sample denotes a preference for over given input .

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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
Ch.2 Generative Models - Foundations of Large Language Models
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Intuition of the Ranking Loss Function in RLHF
Reward Model Training via Ranking Loss Minimization
Reward Model Loss as Negative Log-Likelihood
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An AI team is training a system to learn from human preferences. They have a dataset where for a given input
x, humans consistently prefer responsey_preferredover responsey_rejected. After training, they test two different scoring models, Model A and Model B, on this pair. The models produce the following scores:- Model A:
score(x, y_preferred) = 3.2,score(x, y_rejected) = 1.5 - Model B:
score(x, y_preferred) = -0.5,score(x, y_rejected) = -2.0
Based on these scores, which statement accurately evaluates the models' performance on this specific example?
- Model A:
A reward model is being trained to learn human preferences by minimizing a ranking loss function. This function penalizes the model when the score it assigns to a human-preferred response is not higher than the score for a less-preferred response. Given the same prompt, which of the following scoring outcomes for a preferred/less-preferred pair would incur a penalty from the loss function?
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Choosing and Justifying an RLHF Objective Under Competing Product Constraints
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Root-Cause Analysis of a “Reward Hacking” Spike During RLHF with PPO
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Simplified Notation for Preference Probability Models
Reward Model Loss as Negative Log-Likelihood
Empirical Reward Model Loss Formula using Bradley-Terry Model
A system for evaluating generated text uses a scalar scoring function,
r(input, output), to assign a numerical score to each potential output. For a given input, 'Output A' receives a score of 2.0, and 'Output B' receives a score of -0.2. The system models the probability that one output is preferred over another using the sigmoid of the difference between their scores. Based on this model, what is the approximate probability that 'Output A' is preferred over 'Output B'?Impact of Score Transformation on Preference Probabilities
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Omission of Parameter Superscript in Probability Notation
A preference model calculates the probability that output Y_a is preferred over output Y_b by applying the sigmoid function to the difference in their scalar scores,
score(Y_a) - score(Y_b). If the initial scores for Y_a and Y_b result in a preference probability greater than 50% but less than 100%, which of the following transformations to the scores is guaranteed to leave this probability unchanged?
Learn After
Pair-wise Ranking Loss Formula for RLHF Reward Model
Empirical Reward Model Loss Formula using Bradley-Terry Model
A reward model is trained to learn human preferences by minimizing the following loss function, which is an expectation over a preference dataset :
In this dataset, represents a response preferred over response for a given input . What is the primary effect of successfully minimizing this loss function on the model's behavior?
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Impact of Prediction Confidence on Reward Model Loss