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Regret

As explained in Optimization Algorithms: AI techniques for design, planning, and control problems

Regret is the cumulative difference between the reward obtainable by always choosing the best action and the reward actually obtained.

Regret measures the cumulative reward lost by choosing actions instead of always selecting the best available action. In multi-armed bandits, it exposes the cost of exploration and poor exploitation. section 12.1.6

Three slot machines over 90 trials

Suppose three machines have mean payoffs of 8, 10, and 5. Choosing each machine 30 times produces 690 expected reward, while always choosing machine 2 produces 900. Regret is therefore 900 − 690 = 210. section 12.1.6

Compare strategies by accumulating per-trial regret:

  • Explore-only samples machines randomly, while exploit-only greedy commits to the currently highest-reward choice. section 12.1.6

How Optimization Algorithms: AI techniques for design, planning, and control problems covers it

How deep it goes
Calculates per-trial and average regret with a worked example and Python implementations, but does not develop formal regret bounds.
Examples
Uses three slot machines, 90 trials, payoff distributions, strategy pseudocode, and average-regret outputs.
What it assumes
Assumes familiarity with rewards and repeated choices while introducing exploration, exploitation, payoff distributions, and regret through slot machines.
What you can do after
Diagnose bandit strategies by implementing cumulative and average regret calculations in NumPy.
How it connects
Connects regret with multi-armed bandits, exploration, exploitation, ε-greedy, and upper confidence bound strategies.

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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Optimization Algorithms: AI techniques for design, planning, and control problems. The section links point to the parts of the book it draws on.