Distributed Search Trees: Fault Tolerance in an Asynchronous Environment

We propose a distributed dictionary that allows insert and search operations and that tolerates arbitrary single server crashes. The distinctive feature of our model is that the crash of a server cannot be detected. This is in contrast to all other proposals of distributed fault-tolerant search structures presented thus far. It reflects the real situation in the internet more accurately, and is in general more suitable to complex overall conditions. This makes our solution fundamentally different from all previous ones, but also more complicated. We present in detail the algorithms for searching, insertion, and graceful recovery of crashed server

Distributed search trees: Fault tolerance in an asynchronous environment

ISSN:1432-4350ISSN:1433-049

From Robotics to Facility Location: Contraction Functions, Weber Point, Convex Core

We define and study the concept of Contraction Functions to solve the point formation problem in robotics. Interestingly, the discussion leads to the Weber point that plays an important role in facility location. We introduce the notion of Convex Core and show that this helps to locate the Weber point

Point Formation on a line: Contraction Functions and Weber point

In [Sch03], we introduced the concept of Contraction Functions and Contraction Points to solve the point formation problem. We derived several interesting properties and showed that the Weber point is a contraction point. It is an open question, whether there are contraction points besides the Weber point

Distributed Highly Available Search Trees

We propose a distributed dictionary that tolerates arbitrary single server crashes. The distinctive feature of our model is that the crash of a server cannot be detected. This is in contrast to all other proposals of distributed fault tolerant search structures presented thus far

Equal Sum Subsets: Complexity of Variations

We start an investigation into the complexity of variations of the Equal Sum Subsets problem, a basic problem in which we are given a set of numbers and are asked to find two disjoint subsets of the numbers that add up to the same sum. While Equal Sum Subsets is known to be NP -complete, only very few studies have investigated the complexity of its variations. In this paper, we show NP -completeness for two very natural variations, namely Factor-r Sum Subsets, where we need to find two subsets such that the ratio of their sums is exactly r, and k Equal Sum Subsets, where we need to find k subsets of equal sum. In an effort to gain an intuitive understanding of what makes a variation of Equal Sum Subsets NP -hard, we study several variations of Equal Sum Subsets in which we introduce additional requirements that a solution must fulfill (e.g., the cardinalities of the two sets must differ by exactly one), and prove NP -hardness for these variations. Finally, we investigate and show NP -hardness for the Equal Sum Subsets from Two Sets problem and its variations, where we are given two sets and we need to find two subsets of equal sum

Improving Customer Proximity to Railway Stations

We consider problems of (nev) station placement along (existing) railvay tracks, so as to increase the number of users. We prove that, in spite of the NP-hardness for the general version, some interesting cases can be solved exactly by a suitable dynamic programming approach. For variants in vhich ve also take into account existing connections betveen cities and railvay tracks (streets, buses, etc.) ve instead shov some hardness results