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166
Modeling Component Connectors in Reo by Constraint Automata (Extended Abstract)
, 2004
"... Reo is an exogenous coordination language for compositional construction of component connectors based on a calculus of channels. Building automated tools to address such concerns as equivalence or containment of the behavior of two given connectors, verification of the behavior of a connector, etc. ..."
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Cited by 64 (28 self)
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Reo is an exogenous coordination language for compositional construction of component connectors based on a calculus of channels. Building automated tools to address such concerns as equivalence or containment of the behavior of two given connectors, verification of the behavior of a connector, etc. requires an operational semantic model suitable for model checking. In this paper we introduce constraint automata and propose them as a semantic model for Reo.
BDDbased cryptanalysis of keystream generators
 Advances in Cryptology – EUROCRYPT’02, LNCS 1462
, 2002
"... Abstract. Many of the keystream generators which are used in practice are LFSRbased in the sense that they produce the keystream according to a rule y = C(L(x)), where L(x) denotes an internal linear bitstream, produced by a small number of parallel linear feedback shift registers (LFSRs), and C de ..."
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Cited by 22 (1 self)
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Abstract. Many of the keystream generators which are used in practice are LFSRbased in the sense that they produce the keystream according to a rule y = C(L(x)), where L(x) denotes an internal linear bitstream, produced by a small number of parallel linear feedback shift registers (LFSRs), and C denotes some nonlinear compression function. We present an n O(1) 2 (1−α)/(1+α)n time bounded attack, the FBDDattack, against LFSRbased generators, which computes the secret initial state x ∈ {0, 1} n from cn consecutive keystream bits, where α denotes the rate of information, which C reveals about the internal bitstream, and c denotes some small constant. The algorithm uses Free Binary Decision Diagrams (FBDDs), a data structure for minimizing and manipulating Boolean functions. The FBDDattack yields better bounds on the effective key length for several keystream generators of practical use, so a 0.656n bound for the selfshrinking generator, a 0.6403n bound for the A5/1 generator, used in the GSM standard, a 0.6n bound for the E0 encryption standard in the one level mode, and a 0.8823n bound for the twolevel E0 generator used in the Bluetooth wireless LAN system. 1
TimeSpace Tradeoffs, Multiparty Communication Complexity, and NearestNeighbor Problems
 In 34th Symp. on Theory of Computing (STOC’02
, 2002
"... We extend recent techniques for timespace tradeoff lower bounds using multiparty communication complexity ideas. Using these arguments, for inputs from large domains we prove larger tradeoff lower bounds than previously known for general branching programs, yielding time lower bounds of the form T ..."
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Cited by 19 (1 self)
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We extend recent techniques for timespace tradeoff lower bounds using multiparty communication complexity ideas. Using these arguments, for inputs from large domains we prove larger tradeoff lower bounds than previously known for general branching programs, yielding time lower bounds of the form T = n) when space S = n , up from T = n log n) for the best previous results. We also prove the first unrestricted separation of the power of general and oblivious branching programs by proving that 1GAP , which is trivial on general branching programs, has a timespace tradeoff of the form T = (n=S)) on oblivious Finally, using timespace tradeoffs for branching programs, we improve the lower bounds on query time of data structures for nearest neighbor problems in d dimensions from d= log n), proved in the cellprobe model [8, 5], to d) or log d= log log d) or even d log d) (depending on the metric space involved) in slightly less general but more reasonable data structure models.
Rectangle Size Bounds and Threshold Covers in Communication Complexity
 In Proceedings Eighteenth Annual IEEE Conference on Computational Complexity
, 2003
"... We investigate the power of the most important lower bound technique in randomized communication complexity, which is based on an evaluation of the maximal size of approximately monochromatic rectangles, minimized over all distributions on the inputs. While it is known that the 0error version of th ..."
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Cited by 18 (2 self)
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We investigate the power of the most important lower bound technique in randomized communication complexity, which is based on an evaluation of the maximal size of approximately monochromatic rectangles, minimized over all distributions on the inputs. While it is known that the 0error version of this bound is polynomially tight for deterministic communication, nothing in this direction is known for constant error and randomized communication complexity. We rst study a onesided version of this bound and obtain that its value lies between the MA and AMcomplexities of the considered function. Hence the lower bound actually works for a (communication complexity) class between MA\co MA and AM\co AM . We also show that the MAcomplexity of the disjointness problem is n). Following this we consider the conjecture that the lower bound method is polynomially tight for randomized communication complexity. First we disprove a distributional version of this conjecture. Then we give a combinatorial characterization of the value of the lower bound method, in which the optimization over all distributions is absent. This characterization is done by what we call a uniform threshold cover. We also study relaxations of this notion, namely approximate majority covers and majority covers, and compare these three notions in power, exhibiting exponential separations. Each of these covers captures a lower bound method previously used for randomized communication complexity.
Extracting Certificates from Quantified Boolean Formulas
 In Proc. of 9th International Joint Conference on Artificial Intelligence (IJCAI05
, 2005
"... A certificate of satisfiability for a quantified boolean formula is a compact representation of one of its models which is used to provide solverindependent evidence of satisfiability. In addition, it can be inspected to gather explicit information about the semantics of the formula. Due to the intr ..."
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Cited by 17 (4 self)
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A certificate of satisfiability for a quantified boolean formula is a compact representation of one of its models which is used to provide solverindependent evidence of satisfiability. In addition, it can be inspected to gather explicit information about the semantics of the formula. Due to the intrinsic nature of quantified formulas, such certificates demand much care to be efficiently extracted, compactly represented, and easily queried. We show how to solve all these problems. 1
Comparing Two Implementations of a Complete and BacktrackFree Interactive Configurator
 In: CP’04 CSPIA Workshop
, 2004
"... A product configurator should be complete and backtrack free in the sense that the user can choose freely between any valid configuration and will be prevented from making choices that no valid configuration satisfies. In this paper, we experimentally evaluate a symbolic and searchbased impleme ..."
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Cited by 16 (10 self)
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A product configurator should be complete and backtrack free in the sense that the user can choose freely between any valid configuration and will be prevented from making choices that no valid configuration satisfies. In this paper, we experimentally evaluate a symbolic and searchbased implementation of an interactive product configuration algorithm with these properties. Our results show that the symbolic approach often has several orders of magnitude faster response time than the searchbased approach due to the precompilation of a symbolic representation of the solution space. Moreover, the di#erence between the average and worst response time for the symbolic approach is typically within a factor of two, whereas it for the searchbased approach may be more than two orders of magnitude.
BDDs in a branch and cut framework
 EXPERIMENTAL AND EFFICIENT ALGORITHMS, PROCEEDINGS OF THE 4TH INTERNATIONAL WORKSHOP ON EFFICIENT AND EXPERIMENTAL ALGORITHMS (WEA ’05), VOLUME 3503 OF LECTURE NOTES IN COMPUTER SCIENCE
, 2005
"... Branch & Cut is today’s stateoftheart method to solve 0/1integer linear programs. Important for the success of this method is the generation of strong valid inequalities, which tighten the linear programming relaxation of 0/1IPs and thus allow for early pruning of parts of the search tree ..."
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Cited by 14 (2 self)
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Branch & Cut is today’s stateoftheart method to solve 0/1integer linear programs. Important for the success of this method is the generation of strong valid inequalities, which tighten the linear programming relaxation of 0/1IPs and thus allow for early pruning of parts of the search tree. In this paper we present a novel approach to generate valid inequalities for 0/1IPs which is based on Binary Decision Diagrams (BDDs). BDDs are a datastructure which represents 0/1vectors as paths of a certain acyclic graph. They have been successfully applied in computational logic, hardware verification and synthesis. We implemented our BDD cutting plane generator in a branchandcut framework and tested it on several instances of the MAXONES problem and randomly generated 0/1IPs. Our computational results show that we have developed competitive code for these problems, on which stateoftheart MIPsolvers fall short.
Bounds on the OBDDSize of Integer Multiplication via Universal Hashing
, 2005
"... Bryant [5] has shown that any OBDD for the function MULn−1,n, i.e. the middle bit of the nbit multiplication, requires at least 2 n/8 nodes. In this paper a stronger lower bound of essentially 2 n/2 /61 is proven by a new technique, using a universal family of hash functions. As a consequence, one ..."
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Cited by 13 (1 self)
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Bryant [5] has shown that any OBDD for the function MULn−1,n, i.e. the middle bit of the nbit multiplication, requires at least 2 n/8 nodes. In this paper a stronger lower bound of essentially 2 n/2 /61 is proven by a new technique, using a universal family of hash functions. As a consequence, one cannot hope anymore to verify e.g. 128bit multiplication circuits using OBDDtechniques because the representation of the middle bit of such a multiplier requires more than 3 · 10 17 OBDDnodes. Further, a first nontrivial upper bound of 7/3 · 2 4n/3 for the OBDDsize of MULn−1,n is provided.
Implicit flow maximization by iterative squaring
"... Application areas like logic design and network analysis produce large graphs G = (V, E) on which traditional algorithms, which work on adjacency list representations, are not practicable anymore. These large graphs often contain regular structures that enable compact implicit representations by dec ..."
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Cited by 13 (9 self)
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Application areas like logic design and network analysis produce large graphs G = (V, E) on which traditional algorithms, which work on adjacency list representations, are not practicable anymore. These large graphs often contain regular structures that enable compact implicit representations by decision diagrams like OBDDs [2, 3, 17]. To solve problems on such implicitly given graphs, specialized algorithms are needed. These are considered as heuristics with typically higher worstcase runtimes than traditional methods. In this paper, an implicit algorithm for flow maximization in 0–1 networks is presented, which works on OBDDrepresentations of node and edge sets. Because it belongs to the class of layerednetwork methods, it has to construct blockingflows. In contrast to previous implicit methods, it avoids breadthfirst searches and layerwise proceeding, and uses iterative squaring instead. In this way, the algorithm needs to execute only O(log 2 V ) operations on the OBDDs to obtain a layerednetwork or at least one augmenting path, respectively. Moreover, each OBDDoperation is efficient if the node and edge sets are represented by compact OBDDs during the flow computation. In order to investigate the algorithm’s behavior on large and structured networks, it has been analyzed on grid networks, on which a maximum flow is computed in polylogarithmic time O(log 3 V ) and space O(log 2 V ). In contrast, previous methods need time and space Ω(V  1/2 log V ) on grids, and are beaten also in experiments for V  ≥ 226.
On the Size of Randomized OBDDs and ReadOnce Branching Programs for kStable Functions
 In Proc. of the 16th Ann. Symp. on Theoretical Aspects of Computer Science (STACS), LNCS 1563
, 1999
"... In this paper, a simple technique which unifies the known approaches for proving lower bound results on the size of deterministic, nondeterministic, and randomized OBDDs and kOBDDs is described. ..."
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Cited by 11 (9 self)
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In this paper, a simple technique which unifies the known approaches for proving lower bound results on the size of deterministic, nondeterministic, and randomized OBDDs and kOBDDs is described.