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Determinizing Asynchronous Automata
 Proceedings of the 21st International Colloquium on Automata, Languages and Programming (ICALP'94), Jerusalem (Israel) 1994, number 820 in Lecture
, 1993
"... A concurrent version of a finitestate automaton is a set of processes that cooperate in processing letters of the input. Each letter read prompts some of the processes to synchronize and decide on a joint move according to a nondeterministic transition relation. Such automata are known as asynchro ..."
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A concurrent version of a finitestate automaton is a set of processes that cooperate in processing letters of the input. Each letter read prompts some of the processes to synchronize and decide on a joint move according to a nondeterministic transition relation. Such automata are known as asynchronous automata. The question whether these automata can be determinized while retaining the synchronization structure has already been answered in the positive, but indirectly, by means of sophisticated algebraic techniques. In this paper we present an elementary proof, which generalizes the classic subset construction for finitestate automata. The proof uses in an essential way an earlier finitestate construction by Mukund and Sohoni for maintaining each process's latest knowledge about other processes. Our construction is only doubleexponential and thus is the first to essentially match the lower bound. Computer Science Department, Aarhus University, Ny Munkegade, DK 8000 Aarhus C, ...
Suffix Trees and String Complexity
 Advances in Cryptology: Proc. of EUROCRYPT, LNCS 658
, 1992
"... Let s = (s 1 ; s 2 ; : : : ; s n ) be a sequence of characters where s i 2 Z p for 1 i n. One measure of the complexity of the sequence s is the length of the shortest feedback shift register that will generate s, which is known as the maximum order complexity of s [17, 18]. We provide a proof th ..."
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Let s = (s 1 ; s 2 ; : : : ; s n ) be a sequence of characters where s i 2 Z p for 1 i n. One measure of the complexity of the sequence s is the length of the shortest feedback shift register that will generate s, which is known as the maximum order complexity of s [17, 18]. We provide a proof that the expected length of the shortest feedback register to generate a sequence of length n is less than 2 log p n+ o(1), and also give several other statistics of interest for distinguishing random strings. The proof is based on relating the maximum order complexity to a data structure known as a suffix tree. 1 Introduction A common form of stream cipher are the socalled running key ciphers [4, 9] which are deterministic approximations to the one time pad. A running key cipher generates an ultimately periodic sequence s = (s 1 ; s 2 ; : : : ; s n ), s i 2 Z p ; 1 i n, for a given seed or key K. Encryption is performed as with the one time pad, using s as the key stream, but perfect secu...
Gossiping, Asynchronous Automata and Zielonka's Theorem
 SCHOOL OF MATHEMATICS, SPIC SCIENCE FOUNDATION
, 1994
"... In this paper, we first tackle a natural problem from distributed computing, involving timestamps. We then show that our solution to this problem can be applied to provide a simplified proof of Zielonka's theorema fundamental result in the theory of concurrent systems. Let P = fp 1 ; p 2 ; : ..."
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In this paper, we first tackle a natural problem from distributed computing, involving timestamps. We then show that our solution to this problem can be applied to provide a simplified proof of Zielonka's theorema fundamental result in the theory of concurrent systems. Let P = fp 1 ; p 2 ; : : : ; p N g be a set of computing agents or processes which synchronize with each other from time to time and exchange information about themselves and others. The gossip problem is the following: Whenever a set P ` P meets, the processes in P must decide amongst themselves which of them has the latest information, direct or indirect, about each agent p in the system. We propose an algorithm to solve this problem which is finitestate and local. Formally, this means that our algorithm can be implemented as an asynchronous automaton. Solving the gossip problem appears to be a basic step in tackling other problems involving asynchronous automata. Here, we apply our solution to derive...
DemandDriven Type Analysis for DynamicallyTyped Functional Languages
"... We present a new static type analysis for dynamicallytyped languages that produces high quality results at a cost that remains practicable. The analysis has the ability to adapt to the needs of the optimizer and to the characteristics of the program at hand. The result is an analyzer that quickly t ..."
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We present a new static type analysis for dynamicallytyped languages that produces high quality results at a cost that remains practicable. The analysis has the ability to adapt to the needs of the optimizer and to the characteristics of the program at hand. The result is an analyzer that quickly transforms itself to be better equipped to attack the program. Experiments show that our approach can be pretty clever in the optimizations that it enables.
Computational Complexity of a Fast Viterbi Decoding Algorithm for Stochastic LetterPhoneme Transduction
, 1998
"... This paper describes a modification to, and a fast implementation of, the Viterbi algorithm for use in stochastic lettertophoneme conversion. A straightforward (but unrealistic) implementation of the Viterbi algorithm has a linear time complexity with respect to the length of the letter string, bu ..."
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This paper describes a modification to, and a fast implementation of, the Viterbi algorithm for use in stochastic lettertophoneme conversion. A straightforward (but unrealistic) implementation of the Viterbi algorithm has a linear time complexity with respect to the length of the letter string, but quadratic complexity if we additionally consider the number of lettertophoneme correspondences to be a variable determining the problem size. Since the number of correspondences can be large, processing time is long. If the correspondences are precompiled to a deterministic finitestate automaton to simplify the process of matching to determine state survivors, execution time is reduced by a large multiplicative factor. Speedup is inferred indirectly since the straightforward implementation of Viterbi decoding is too slow for practical comparison, and ranges between about 200 and 4000 depending upon the number of letters processed and the particular correspondences employed in the transdu...
Indexing Factors in DNA/RNA Sequences
"... Abstract. In this paper, we present the Truncated Generalized Suffix Automaton (TGSA) and present an efficient online algorithm for its construction. TGSA is a novel type of finite automaton suitable for indexing DNA and RNA sequences, where the text is degenerate i.e. contains sets of characters. ..."
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Abstract. In this paper, we present the Truncated Generalized Suffix Automaton (TGSA) and present an efficient online algorithm for its construction. TGSA is a novel type of finite automaton suitable for indexing DNA and RNA sequences, where the text is degenerate i.e. contains sets of characters. TGSA indexes the so called kfactors, the factors of the degenerate text with length not exceeding a given constant k. The presented algorithm works in O(n 2) time, where n is the length of the input DNA/RNA sequence. The resulting TGSA has at most linear number of states with respect to the length of the text. TGSA enables us to find the list occ (u) of all occurrences of a given pattern u in degenerate text ˜x in time u  + occ (u). 1