Queue Layouts of Hypercubes

  • Authors:
  • Petr Gregor;Riste Škrekovski;Vida Vukašinović

  • Affiliations:
  • gregor@ktiml.mff.cuni.cz;skrekovski@gmail.com;vida.vukasinovic@gmail.com

  • Venue:
  • SIAM Journal on Discrete Mathematics
  • Year:
  • 2012

Quantified Score

Hi-index 0.00

Visualization

Abstract

A queue layout of a graph consists of a linear ordering $\sigma$ of its vertices and a partition of its edges into sets, called queues, such that in each set no two edges are nested with respect to $\sigma$. We show that the $n$-dimensional hypercube $Q_n$ has a layout into $n-\lfloor \log_2 n \rfloor$ queues for all $n\ge 1$. On the other hand, for every $\varepsilon0$, every queue layout of $Q_n$ has more than $(\frac{1}{2}-\varepsilon) n-O(1/\varepsilon)$ queues and, in particular, more than $(n-2)/3$ queues. This improves previously known upper and lower bounds on the minimal number of queues in a queue layout of $Q_n$. For the lower bound we employ a new technique of out-in representations and contractions which may be of independent interest.