Core Concepts
Closing the gap between directed hopsets and shortcut sets through innovative construction techniques.
Abstract
The content discusses the tradeoff between optimal size of hopsets and shortcut sets in directed graphs. It introduces a new hopset construction method to bridge the gap between these two concepts. The analysis is structured into sections detailing technical overview, proof of theorem, hopset size analysis, constructing the path, and more.
Introduction:
Reachability and shortest paths in directed graphs are fundamental.
Dependency on few edges motivated shortcut sets.
Generalization to distances led to hopsets.
Technical Overview:
Proof of Theorem 1.1 presented.
Hopset construction detailed in two parts: using existing methods and introducing new edges.
Proof of Theorem 1.1:
Backward Shortcutting Subroutine guarantees small-hop paths.
Hierarchical sampling for many-hop detours explained.
Hopset Size Analysis:
Calculation of total number of hopset edges based on types.
Constructing the Path:
Algorithm for building a path from source to target along R(s, t).
Differentiating easy and hard intervals on R(s, t) for efficient construction.
Stats
Hopset edges: O(n log n), O(n2 log6 n log(nW)/(ε2β3)), O(n log2(nW) log3 n/ε2)
Quotes
"Shortcuts sets / hopsets form core algorithms for reachability / shortest paths." - Authors