Sharp Noisy Binary Search with Monotonic Probabilities
- URL: http://arxiv.org/abs/2311.00840v1
- Date: Wed, 1 Nov 2023 20:45:13 GMT
- Title: Sharp Noisy Binary Search with Monotonic Probabilities
- Authors: Lucas Gretta, Eric Price
- Abstract summary: We revisit the noisy binary search model of Karp and Kleinberg.
We produce an algorithm that succeeds with probability $1-delta$ from [ frac1C_tau, varepsilon cdot left(lg n + O(log2/3 n log 1/3 frac1delta + log frac1delta) right.
- Score: 5.563988395126509
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: We revisit the noisy binary search model of Karp and Kleinberg, in which we
have $n$ coins with unknown probabilities $p_i$ that we can flip. The coins are
sorted by increasing $p_i$, and we would like to find where the probability
crosses (to within $\varepsilon$) of a target value $\tau$. This generalized
the fixed-noise model of Burnashev and Zigangirov , in which $p_i = \frac{1}{2}
\pm \varepsilon$, to a setting where coins near the target may be
indistinguishable from it. Karp and Kleinberg showed that
$\Theta(\frac{1}{\varepsilon^2} \log n)$ samples are necessary and sufficient
for this task.
We produce a practical algorithm by solving two theoretical challenges:
high-probability behavior and sharp constants. We give an algorithm that
succeeds with probability $1-\delta$ from
\[
\frac{1}{C_{\tau, \varepsilon}} \cdot \left(\lg n + O(\log^{2/3} n \log^{1/3}
\frac{1}{\delta} + \log \frac{1}{\delta})\right)
\]
samples, where $C_{\tau, \varepsilon}$ is the optimal such constant
achievable. For $\delta > n^{-o(1)}$ this is within $1 + o(1)$ of optimal, and
for $\delta \ll 1$ it is the first bound within constant factors of optimal.
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