ConceptApproximation Ratio
Approximation Ratio
A common metric for measuring the gap between an algorithm's performance and that of a theoretically optimal algorithm. In best-arm identification it is defined as the ratio of the algorithm's normalized error exponent to the optimal value; the closer to 1, the closer to fully adaptive.
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Nov 4
For a fixed m, the algorithm achieves an approximation ratio of (1-c_m)/(2-c_m) (ignoring estimation error), and this factor approaches 1/2 as c_m decreases.
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