Searching with increasing speeds

Leszek Gąsieniec, Shuji Kijima, Jie Min

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Scopus citations


In the classical search problem on the line or in higher dimension one is asked to find the shortest (and often the fastest) route to be adopted by a robot R from the starting point s towards the target point t located at unknown location and distance D. It is usually assumed that robot R moves with a fixed unit speed 1. It is well known that one can adopt a “zig-zag” strategy based on the exponential expansion, which allows to reach the target located on the line in time ≤9D and this bound is tight. The problem was also studied in two dimensions where the competitive factor is known to be O(D). In this paper we study an alteration of the search problem in which robot R starts moving with the initial speed 1. However, during search it can encounter a point or a sequence of points enabling faster and faster movement. The main goal is to adopt the route which allows R to reach the target t as quickly as possible. We study two variants of the considered search problem: (1) with the global knowledge and (2) with the local knowledge. In variant (1) robot R knows a priori the location of all intermediate points as well as their expulsion speeds. In this variant we study the complexity of computing optimal search trajectories. In variant (2) the relevant information about points in P is acquired by R gradually, i.e., while moving along the adopted trajectory. Here the focus is on the competitive factor of the solution, i.e., the ratio between the solutions computed in variants (2) and (1). We also consider two types of search spaces with points distributed on the line and subsequently with points distributed in two-dimensional space.

Original languageEnglish (US)
Title of host publicationStabilization, Safety, and Security of Distributed Systems - 20th International Symposium, SSS 2018, Proceedings
EditorsTaisuke Izumi, Petr Kuznetsov
PublisherSpringer Verlag
Number of pages13
ISBN (Print)9783030032319
StatePublished - 2018
Externally publishedYes
Event20th International Symposium on Stabilization, Safety, and Security of Distributed Systems, SSS 2018 - Tokyo, Japan
Duration: Nov 4 2018Nov 7 2018

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume11201 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference20th International Symposium on Stabilization, Safety, and Security of Distributed Systems, SSS 2018


  • 2d space
  • Increasing speeds
  • Line
  • Search problem

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)


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