,
Ron Rothblum
Creative Commons Attribution 4.0 International license
We study the circuit complexity of the multiselection problem: given an input string x ∈ {0,1}ⁿ along with indices i_1,… ,i_q ∈ [n], output (x_{i_1},… ,x_{i_q}). A trivial lower bound for the circuit size is the input length n + q⋅log(n), but the straightforward construction has size Θ(q⋅n).
Our main result is an O(n+q⋅log³(n))-size and O(log(n+q))-depth circuit for multiselection. In particular, for any q ≤ n/log³(n) the circuit has linear size and logarithmic depth. Prior to our work no linear-size circuit for multiselection was known for any q = ω(1) and regardless of depth.
@InProceedings{holmgren_et_al:LIPIcs.CCC.2024.11,
author = {Holmgren, Justin and Rothblum, Ron},
title = {{Linear-Size Boolean Circuits for Multiselection}},
booktitle = {39th Computational Complexity Conference (CCC 2024)},
pages = {11:1--11:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-331-7},
ISSN = {1868-8969},
year = {2024},
volume = {300},
editor = {Santhanam, Rahul},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CCC.2024.11},
URN = {urn:nbn:de:0030-drops-204070},
doi = {10.4230/LIPIcs.CCC.2024.11},
annote = {Keywords: Private Information Retrieval, Batch Selection, Boolean Circuits}
}