Deterministic $(2k-1)$-competitive online transportation algorithm

Determine whether online metric transportation admits a deterministic $(2k-1)$-competitive algorithm, matching the known lower bound and yielding a competitive guarantee independent of the total capacity.

Background

The online metric transportation problem assigns sequentially arriving requests to kk capacitated server locations in a metric space. The competitive ratio is measured against an offline optimum that knows the entire request sequence, and the desired bound should depend on the number of server locations kk rather than the total capacity nn.

A deterministic (2k−1)(2k-1) lower bound is known, and the cited conjecture proposes that this lower bound is achievable. Prior to the paper, deterministic upper bounds had reached $8k-7$; the paper improves this to approximately $6.6604k-2.89$ but does not establish the conjectured exact bound.

References

conjectured that online transportation admits a deterministic $(2k-1)$-competitive algorithm, matching the known lower bound. Obtaining a guarantee linear in $k$, independently of the total capacity, remained open for more than two decades.

— A Robustified Greedy Algorithm for Online Transportation with Improved Competitive Guarantees  (2609.39052 - Seth et al., 30 Sep 2026) in Introduction