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33
Timespace tradeo s for undirected graph traversal
 In Proceedings 31st Annual Symposium on Foundations of Computer Science
, 1990
"... We investigate timespace tradeo s for traversing undirected graphs, using a variety of structured models that are all variants of Cook and Racko 's \Jumping Automata for Graphs". Our strongest tradeo is a quadratic lower bound on the product of time and space for graph traversal. For example, achie ..."
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We investigate timespace tradeo s for traversing undirected graphs, using a variety of structured models that are all variants of Cook and Racko 's \Jumping Automata for Graphs". Our strongest tradeo is a quadratic lower bound on the product of time and space for graph traversal. For example, achieving linear time requires linear space, implying that depth rst search is optimal. Since our bound in fact applies to nondeterministic algorithms for nonconnectivity, it also implies that closure under complementation of nondeterministic spacebounded complexity classes is achieved only at the expense of increased time. To demonstrate that these structured models are realistic, we also investigate their power. In addition to admitting well known algorithms such as depth rst search and random walk, we show that one simple variant of this model is nearly as powerful as a Turing machine. Speci cally, for general undirected graph problems, it can simulate a Turing machine with only a constant factor increase in space and a polynomial factor increase in time.
Optimal TimeSpace TradeOffs for NonComparisonBased Sorting ∗
, 2001
"... Reproduction of all or part of this work is permitted for educational or research use on condition that this copyright notice is included in any copy. See back inner page for a list of recent BRICS Report Series publications. Copies may be obtained by contacting: BRICS ..."
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Reproduction of all or part of this work is permitted for educational or research use on condition that this copyright notice is included in any copy. See back inner page for a list of recent BRICS Report Series publications. Copies may be obtained by contacting: BRICS
BDDs  Design, Analysis, Complexity, and Applications
 Discrete Applied Mathematics 138
, 2004
"... BDDs (binary decision diagrams) and their variants are the most frequently used representation types or data structures for boolean functions. Research on BDD variants has turned out to be one of the areas where the symbiosis between theoretical investigations in algorithm design and analysis, compl ..."
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BDDs (binary decision diagrams) and their variants are the most frequently used representation types or data structures for boolean functions. Research on BDD variants has turned out to be one of the areas where the symbiosis between theoretical investigations in algorithm design and analysis, complexity theory, and applications has led to progress in theory and in applications. Here the different roots of the interest in BDDs are described, the main BDD variants and their algorithmic properties are presented, the representation size of selected functions is investigated, lower bound techniques are discussed and applications to algorithmic graph problems and hardware verification problems are presented.
Approximation of Boolean Functions by Combinatorial Rectangles
 Electr. Coll. on Comp. Compl
, 2000
"... This paper deals with the number of monochromatic combinatorial rectangles required to approximate a Boolean function on a constant fraction of all inputs, where each rectangle may be defined with respect to its own partition of the input variables. The main result of the paper is that the number of ..."
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This paper deals with the number of monochromatic combinatorial rectangles required to approximate a Boolean function on a constant fraction of all inputs, where each rectangle may be defined with respect to its own partition of the input variables. The main result of the paper is that the number of rectangles required for the approximation of Boolean functions in this model is very sensitive to the allowed error: There is an explicitly defined sequence of functions f n : {0, 1} n # {0, 1} such that f n has rectangle approximations with a constant number of rectangles and onesided error 1/3+o(1) or twosided error 1/4+2 #(n) , but, on the other hand, f n requires exponentially many rectangles if the error bounds are decreased by an arbitrarily small constant. Rectangle partitions and rectangle approximations with the same partition of the input variables for all rectangles have been thoroughly investigated in communication complexity theory. The complexity measures where each r...
Binary Decision Diagrams
"... Decision diagrams are a natural representation of finite functions. The obvious complexity measures are length and size which correspond to time and space of computations. Decision diagrams are the right model for considering space lower bounds and timespace tradeoffs. Due to the lack of powerful ..."
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Decision diagrams are a natural representation of finite functions. The obvious complexity measures are length and size which correspond to time and space of computations. Decision diagrams are the right model for considering space lower bounds and timespace tradeoffs. Due to the lack of powerful lower bound techniques, various types of restricted decision diagrams are investigated. They lead to new lower bound techniques and some of them allow efficient algorithms for a list of operations on boolean functions. Indeed, restricted decision diagrams like ordered binary decision diagrams (OBDDs) are the most common data structure for boolean functions with many applications in verification, model checking, CAD tools, and graph problems. From a complexity theoretical point of view also randomized and nondeterministic decision diagrams are of interest. 1
Some Topics in Parallel Computation and Branching Programs
, 1995
"... Some Topics in Parallel Computation and Branching Programs by Rakesh Kumar Sinha Chairperson of the Supervisory Committee: Professor Paul Beame Department of Computer Science and Engineering There are two parts of this thesis: the first part gives two constructions of branching programs; the second ..."
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Some Topics in Parallel Computation and Branching Programs by Rakesh Kumar Sinha Chairperson of the Supervisory Committee: Professor Paul Beame Department of Computer Science and Engineering There are two parts of this thesis: the first part gives two constructions of branching programs; the second part contains three results on models of parallel machines. The branching program model has turned out to be very useful for understanding the computational behavior of problems. In addition, several restrictions of branching programs, for example ordered binary decision diagrams, have proven to be successful data structures in several VLSI design and verification applications. We construct a branching program of o(n log 3 n) nodes for computing any threshold function on n variables and a branching program of o(n log 4 n) nodes for determining the sum of n variables modulo a fixed divisor. These are improvements over constructions of size 2(n 3=2 ) due to Lupanov [Lup65]. The second p...
Computing Jacobi Symbols Modulo Sparse Integers And Polynomials And Some Applications
 J. Algorithms
"... We describe a polynomial time algorithm to compute Jacobi symbols of exponentially large integers of special form, including socalled sparse integers which are exponentially large integers with only polynomially many nonzero binary digits. In a number of papers sequences of Jacobi symbols have bee ..."
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We describe a polynomial time algorithm to compute Jacobi symbols of exponentially large integers of special form, including socalled sparse integers which are exponentially large integers with only polynomially many nonzero binary digits. In a number of papers sequences of Jacobi symbols have been proposed as generators of cryptographically secure pseudorandom bits. Our algorithm allows us to use much larger moduli in such constructions. We also use our algorithm to design a probabilistic polynomial time test which decides if a given integer of the aforementioned type is a perfect square (assuming the Extended Riemann Hypothesis). We also obtain analogues of these results for polynomials over finite fields. Moreover, in this case the perfect square testing algorithm is unconditional. These results can be compared with many known NPhardness results for some natural problems on sparse integers and polynomials.
Amplifying Circuit Lower Bounds Against Polynomial Time With Applications
 In IEEE Conference on Computational Complexity
"... We give a selfreduction for the Circuit Evaluation problem (CircEval), and prove the following consequences. • Amplifying SizeDepth Lower Bounds. If CircEval has Boolean circuits of n k size and n1−δ depth for some k and δ, then for every ε> 0, there is a δ ′> 0 such that CircEval has circuits of ..."
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We give a selfreduction for the Circuit Evaluation problem (CircEval), and prove the following consequences. • Amplifying SizeDepth Lower Bounds. If CircEval has Boolean circuits of n k size and n1−δ depth for some k and δ, then for every ε> 0, there is a δ ′> 0 such that CircEval has circuits of n1+ε size and n1−δ ′ depth. Moreover, the resulting circuits require only Õ(nε) bits of nonuniformity to construct. As a consequence, strong enough depth lower bounds for Circuit Evaluation imply a full separation of P and NC (even with a weak size lower bound). • Lower Bounds for Quantified Boolean Formulas. Let c, d> 1 and e < 1 satisfy c < (1 − e + d)/d. Either the problem of recognizing valid quantified Boolean formulas (QBF) is not solvable in TIME[n c], or the Circuit Evaluation problem cannot be solved with circuits of n d size and n e depth. This implies unconditional polynomialtime uniform circuit lower bounds for solving QBF. We also prove that QBF does not have n ctime uniform NC circuits, for all c < 2. 1
PolynomialSize Binary Decision Diagrams for
, 2004
"... Binary decision diagrams (BDDs) are graphbased data structures representing Boolean functions; `BDDs are BDDs with an additional restriction that each input bit can be tested at most ` times. A d uniform hypergraph H on N vertices is an exactly halfdhyperclique if N=2 of its vertices form a ..."
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Binary decision diagrams (BDDs) are graphbased data structures representing Boolean functions; `BDDs are BDDs with an additional restriction that each input bit can be tested at most ` times. A d uniform hypergraph H on N vertices is an exactly halfdhyperclique if N=2 of its vertices form a hyperclique and the remaining vertices are isolated. Wegener [J. ACM 35(2) (1988), 461471] conjectured that there is no polynomialsize (d 1)BDD for the Exactly half dhyperclique problem. We disprove this conjecture by constructing polynomialsize 2BDDs for the Exactly halfdhyperclique problem for every d 2. Our construction is based on a new idea involving logspace algorithms with faulty inputs.
TimeSpace Tradeoffs for Set Operations
, 1994
"... This paper considers timespace tradeoffs for various set operations. Denoting the time requirement of an algorithm by T and its space requirement by S, it is shown that TS =\Omega (n 2 ) for set complementation and TS =\Omega \Gamma n 3=2 \Delta for set intersection, in the Rway branch ..."
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This paper considers timespace tradeoffs for various set operations. Denoting the time requirement of an algorithm by T and its space requirement by S, it is shown that TS =\Omega (n 2 ) for set complementation and TS =\Omega \Gamma n 3=2 \Delta for set intersection, in the Rway branching program model. In the more restricted model of comparison branching programs, the paper provides two additional types of results. A tradeoff of TS =\Omega \Gamma n 2\Gammaffl(n) \Delta , derived from Yao's lower bound for element distinctness, is shown for set disjointness, set union and set intersection (where ffl(n) = O \Gamma (log n) \Gamma1=2 \Delta ). A bound of TS =\Omega \Gamma n 3=2 \Delta is shown for deciding set equality and set inclusion. Finally, a classification of set operations is presented, and it is shown that all problems of a large naturally arising class are as hard as the problems bounded in this paper.