Dueling DQN explained from scratch: why splitting state value from advantage beats classic DQN

East-Muffin-6472 · reddit · 2026-11-10

Continuing an "RL From Scratch" series, the author published notes on Dueling DQN, covering the what/why/how versus Double DQN and vanilla DQN:

• What: still off-policy, model-free, value-based — only the last layer of the Q-Network changes, mainly for optimization
• Core question: do we really need Q(s,a) for every action in every state? A car on a highway shows state value (road, steering) can matter far more than individual action values, especially with a wall ahead
• Key concepts: advantage (A(s,a)=Q(s,a)−V(s)), identifiability, the two-head trunk/value/advantage split, and the aggregation rule Q=V+A−mean A
• Comes with theory, code, math, and a playground to train a live agent

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