Affiliation:
1. UC Berkeley, Berkeley, California, USA
2. Duke University and Emerald Innovations, Durham, North Carolina, USA
3. Duke University, Durham, North Carolina, USA
Abstract
This article presents
universal
algorithms for clustering problems, including the widely studied
k
-median,
k
-means, and
k
-center objectives. The input is a metric space containing all
potential
client locations. The algorithm must select
k
cluster centers such that they are a good solution for
any
subset of clients that actually realize. Specifically, we aim for low
regret
, defined as the maximum over all subsets of the difference between the cost of the algorithm’s solution and that of an optimal solution. A universal algorithm’s solution
Sol
for a clustering problem is said to be an α , β-approximation if for all subsets of clients
C
′
, it satisfies
sol
(
C
′
) ≤ α ċ
opt
(
C
′) + β ċ
mr
, where
opt
(
C
′ is the cost of the optimal solution for clients (
C
′) and
mr
is the minimum regret achievable by any solution.
Our main results are universal algorithms for the standard clustering objectives of
k
-median,
k
-means, and
k
-center that achieve (
O
(1),
O
(1))-approximations. These results are obtained via a novel framework for universal algorithms using linear programming (LP) relaxations. These results generalize to other ℓ
p
-objectives and the setting where some subset of the clients are
fixed
. We also give hardness results showing that (α, β)-approximation is NP-hard if α or β is at most a certain constant, even for the widely studied special case of Euclidean metric spaces. This shows that in some sense, (
O
(1),
O
(1))-approximation is the strongest type of guarantee obtainable for universal clustering.
Funder
NSF
NSF CAREER
Indo-US Virtual Networked Joint Center on Algorithms
Publisher
Association for Computing Machinery (ACM)
Subject
Mathematics (miscellaneous)
Cited by
1 articles.
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