Solution to KL Divergence Minimization for Policy Optimization
The optimization problem of minimizing the Kullback-Leibler (KL) divergence between a learned policy and an optimal policy is uniquely solved when the two probability distributions are identical. Thus, the optimal target policy is defined by equating it to , which incorporates the reward-weighted reference policy and the normalization factor. This relationship is formally given by:

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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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Solution to KL Divergence Minimization for Policy Optimization
When optimizing a policy π_θ to match an optimal policy π*, the objective function is often simplified from Objective A to Objective B:
Objective A:
arg min_θ Eₓ[KL(π_θ(·|x) || π*(·|x)) - log Z(x)]Objective B:arg min_θ Eₓ[KL(π_θ(·|x) || π*(·|x))]What is the fundamental mathematical reason this simplification is valid?
Efficiency in Policy Optimization Implementation
Justification for Simplification in Policy Optimization
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Reward Function in Terms of Policy Models and Normalization Factor
In a particular policy optimization framework, the target policy, denoted as , is determined by the following relationship involving a reference policy , a reward function , a positive temperature parameter , and a normalization term : Given this formula, what is the primary effect of significantly increasing the reward for a single, specific output , while keeping all other factors constant?
Consider the following equation that defines a target policy based on a reference policy , a reward function , a positive scaling parameter , and a normalization term : True or False: If the reward function is equal to zero for all possible outputs given an input , the target policy will be identical to the reference policy .
Impact of the Scaling Parameter on Policy Behavior