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SybilInfer: Detecting Sybil Nodes using Social Networks
"... SybilInfer is an algorithm for labelling nodes in a social network as honest users or Sybils controlled by an adversary. At the heart of SybilInfer lies a probabilistic model of honest social networks, and an inference engine that returns potential regions of dishonest nodes. The Bayesian inference ..."
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Cited by 109 (9 self)
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SybilInfer is an algorithm for labelling nodes in a social network as honest users or Sybils controlled by an adversary. At the heart of SybilInfer lies a probabilistic model of honest social networks, and an inference engine that returns potential regions of dishonest nodes. The Bayesian inference approach to Sybil detection comes with the advantage label has an assigned probability, indicating its degree of certainty. We prove through analytical results as well as experiments on simulated and realworld network topologies that, given standard constraints on the adversary, SybilInfer is secure, in that it successfully distinguishes between honest and dishonest nodes and is not susceptible to manipulation by the adversary. Furthermore, our results show that SybilInfer outperforms state of the art algorithms, both in being more widely applicable, as well as providing vastly more accurate results. 1
Adaptive Functional Programming
 IN PROCEEDINGS OF THE 29TH ANNUAL ACM SYMPOSIUM ON PRINCIPLES OF PROGRAMMING LANGUAGES
, 2001
"... An adaptive computation maintains the relationship between its input and output as the input changes. Although various techniques for adaptive computing have been proposed, they remain limited in their scope of applicability. We propose a general mechanism for adaptive computing that enables one to ..."
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Cited by 78 (23 self)
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An adaptive computation maintains the relationship between its input and output as the input changes. Although various techniques for adaptive computing have been proposed, they remain limited in their scope of applicability. We propose a general mechanism for adaptive computing that enables one to make any purelyfunctional program adaptive. We show
An experimental analysis of selfadjusting computation
 In Proceedings of the ACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI
, 2006
"... Selfadjusting computation uses a combination of dynamic dependence graphs and memoization to efficiently update the output of a program as the input changes incrementally or dynamically over time. Related work showed various theoretical results, indicating that the approach can be effective for a r ..."
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Cited by 50 (24 self)
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Selfadjusting computation uses a combination of dynamic dependence graphs and memoization to efficiently update the output of a program as the input changes incrementally or dynamically over time. Related work showed various theoretical results, indicating that the approach can be effective for a reasonably broad range of applications. In this article, we describe algorithms and implementation techniques to realize selfadjusting computation and present an experimental evaluation of the proposed approach on a variety of applications, ranging from simple list primitives to more sophisticated computational geometry algorithms. The results of the experiments show that the approach is effective in practice, often offering orders of magnitude speedup from recomputing the output from scratch. We believe this is the first experimental evidence that incremental computation of any type is effective in practice for a reasonably broad set of applications.
Differential dataflow
"... Existing computational models for processing continuously changing input data are unable to efficiently support iterative queries except in limited special cases. This makes it difficult to perform complex tasks, such as socialgraph analysis on changing data at interactive timescales, which would g ..."
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Cited by 24 (1 self)
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Existing computational models for processing continuously changing input data are unable to efficiently support iterative queries except in limited special cases. This makes it difficult to perform complex tasks, such as socialgraph analysis on changing data at interactive timescales, which would greatly benefit those analyzing the behavior of services like Twitter. In this paper we introduce a new model called differential computation, which extends traditional incremental computation to allow arbitrarily nested iteration, and explain—with reference to a publicly available prototype system called Naiad—how differential computation can be efficiently implemented in the context of a declarative dataparallel dataflow language. The resulting system makes it easy to program previously intractable algorithms such as incrementally updated strongly connected components, and integrate them with data transformation operations to obtain practically relevant insights from real data streams. 1.
Two for the price of one: A model for parallel and incremental computation
 In ACMSIGPLANConferenceonObjectOrientedProgramming,Systems, Languages, andApplications
, 2011
"... Parallel or incremental versions of an algorithm can significantly outperform their counterparts, but are often difficult to develop. Programming models that provide appropriate abstractions to decompose data and tasks can simplify parallelization. We show in this work that the same abstractions can ..."
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Cited by 15 (2 self)
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Parallel or incremental versions of an algorithm can significantly outperform their counterparts, but are often difficult to develop. Programming models that provide appropriate abstractions to decompose data and tasks can simplify parallelization. We show in this work that the same abstractions can enable both parallel and incremental execution. We present a novel algorithm for parallel selfadjusting computation. This algorithm extends a deterministic parallel programming model (concurrent revisions) with support for recording and repeating computations. On record, we construct a dynamic dependence graph of the parallel computation. On repeat, we reexecute only parts whose dependencies have changed. We implement and evaluate our idea by studying five example programs, including a realistic multipass CSS layout algorithm. We describe programming techniques that proved particularly useful to improve the performance of selfadjustment in practice. Our final results show significant speedups on all examples (up to 37x on an 8core machine). These speedups are well beyond what can be achieved by parallelization alone, while requiring a comparable effort by the programmer.
Kinetic algorithms via selfadjusting computation
 In Proceedings of the 14th Annual European Symposium on Algorithms (ESA 2006
, 2006
"... Abstract. Define a static algorithm as an algorithm that computes some combinatorial property of its input consisting of static, i.e., nonmoving, objects. In this paper, we describe a technique for syntactically transforming static algorithms into kinetic algorithms, which compute properties of mov ..."
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Cited by 12 (9 self)
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Abstract. Define a static algorithm as an algorithm that computes some combinatorial property of its input consisting of static, i.e., nonmoving, objects. In this paper, we describe a technique for syntactically transforming static algorithms into kinetic algorithms, which compute properties of moving objects. The technique o«ers capabilities for composing kinetic algorithms, for integrating dynamic and kinetic changes, and for ensuring robustness even with fixedprecision floatingpoint arithmetic. To evaluate the e«ectiveness of the approach, we implement a library for performing the transformation, transform a number of algorithms, and give an experimental evaluation. The results show that the technique performs well in practice. 1
A Proposal for Parallel SelfAdjusting Computation
, 2002
"... We present an overview of our ongoing work on parallelizing selfadjustingcomputation techniques. In selfadjusting computation, programs can respond to changes to their data (e.g., inputs, outcomes of comparisons) automatically by running a changepropagation algorithm. This ability is important i ..."
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Cited by 10 (5 self)
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We present an overview of our ongoing work on parallelizing selfadjustingcomputation techniques. In selfadjusting computation, programs can respond to changes to their data (e.g., inputs, outcomes of comparisons) automatically by running a changepropagation algorithm. This ability is important in applications where inputs change slowly over time. All previously proposed selfadjusting computation techniques assume a sequential execution model. We describe techniques for writing parallel selfadjusting programs and a change propagation algorithm that can update computations in parallel. We describe a prototype implementation and present preliminary experimental results.
HigherOrder Functional Reactive Programming in Bounded Space
"... Functional reactive programming (FRP) is an elegant and successful approach to programming reactive systems declaratively. The high levels of abstraction and expressivity that make FRP attractive as a programming model do, however, often lead to programs whose resource usage is excessive and hard to ..."
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Cited by 9 (2 self)
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Functional reactive programming (FRP) is an elegant and successful approach to programming reactive systems declaratively. The high levels of abstraction and expressivity that make FRP attractive as a programming model do, however, often lead to programs whose resource usage is excessive and hard to predict. In this paper, we address the problem of space leaks in discretetime functional reactive programs. We present a functional reactive programming language that statically bounds the size of the dataflow graph a reactive program creates, while still permitting use of higherorder functions and highertype streams such as streams of streams. We achieve this with a novel linear type theory that both controls allocation and ensures that all recursive definitions are wellfounded. We also give a denotational semantics for our language by combining recent work on metric spaces for the interpretation of higherorder causal functions with lengthspace models of spacebounded computation. The resulting category is doubly closed and hence forms a model of the logic of bunched implications.
Dynamic wellspaced point sets
 In SCG ’10: Proceedings of the 26th Annual Symposium on Computational Geometry
, 2010
"... In a wellspaced point set the Voronoi cells all have bounded aspect ratio, i.e., the distance from the Voronoi site to the farthest point in the Voronoi cell divided by the distance to the nearest neighbor in the set is bounded by a small constant. Wellspaced point sets satisfy some important geom ..."
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Cited by 9 (5 self)
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In a wellspaced point set the Voronoi cells all have bounded aspect ratio, i.e., the distance from the Voronoi site to the farthest point in the Voronoi cell divided by the distance to the nearest neighbor in the set is bounded by a small constant. Wellspaced point sets satisfy some important geometric properties and yield quality Voronoi or simplicial meshes that can be important in scientific computations. In this paper, we consider the dynamic wellspaced pointsets problem, which requires computing the wellspaced superset of a dynamically changing input set, e.g., as points are inserted or deleted. We present a dynamic algorithm that allows inserting/deleting points into/from the input in worstcase O(log ∆) time, where ∆ is the geometric spread, a natural measure that is bounded by O(log n) when input points are represented by logsize words. We show that the runtime of the dynamic update algorithm is optimal in the worst case by showing that there exists inputs and modifications that require Ω(log ∆) Steiner points to be inserted to the output. Our algorithm generates sizeoptimal outputs: the resulting output sets are never more than a constant factor larger than the minimum size necessary. A preliminary implementation indicates that the algorithm is indeed fast in practice. To the best of our knowledge, this is the first time and sizeoptimal dynamic algorithm for wellspaced point sets.
Robust kinetic convex hulls in 3D
 In Proceedings of the 16th Annual European Symposium on Algorithms
"... Abstract. Kinetic data structures provide a framework for computing combinatorial properties of continuously moving objects. Although kinetic data structures for many problems have been proposed, some difficulties remain in devising and implementing them, especially robustly. One set of difficulties ..."
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Cited by 9 (4 self)
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Abstract. Kinetic data structures provide a framework for computing combinatorial properties of continuously moving objects. Although kinetic data structures for many problems have been proposed, some difficulties remain in devising and implementing them, especially robustly. One set of difficulties stems from the required update mechanisms used for processing certificate failures—devising efficient update mechanisms can be difficult, especially for sophisticated problems such as those in 3D. Another set of difficulties arises due to the strong assumption in the framework that the update mechanism is invoked with a single event. This assumption requires ordering the events precisely, which is generally expensive. This assumption also makes it difficult to deal with simultaneous events that arise due to degeneracies or due to intrinsic properties of the kinetized algorithms. In this paper, we apply advances on selfadjusting computation to provide a robust motion simulation technique that combines kinetic eventbased scheduling and the classic idea of fixedtime sampling. The idea is to divide time into a lattice of fixedsize intervals, and process events at the resolution of an interval. We apply the approach to the problem of kinetic maintenance of convex hulls in 3D, a problem that has been open since 90s. We evaluate the effectiveness of the proposal experimentally. Using the approach, we are able to run simulations consisting of tens of thousands of points robustly and efficiently. 1