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Algorithms for the Satisfiability (SAT) Problem: A Survey
 DIMACS Series in Discrete Mathematics and Theoretical Computer Science
, 1996
"... . The satisfiability (SAT) problem is a core problem in mathematical logic and computing theory. In practice, SAT is fundamental in solving many problems in automated reasoning, computeraided design, computeraided manufacturing, machine vision, database, robotics, integrated circuit design, compute ..."
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Cited by 125 (3 self)
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. The satisfiability (SAT) problem is a core problem in mathematical logic and computing theory. In practice, SAT is fundamental in solving many problems in automated reasoning, computeraided design, computeraided manufacturing, machine vision, database, robotics, integrated circuit design, computer architecture design, and computer network design. Traditional methods treat SAT as a discrete, constrained decision problem. In recent years, many optimization methods, parallel algorithms, and practical techniques have been developed for solving SAT. In this survey, we present a general framework (an algorithm space) that integrates existing SAT algorithms into a unified perspective. We describe sequential and parallel SAT algorithms including variable splitting, resolution, local search, global optimization, mathematical programming, and practical SAT algorithms. We give performance evaluation of some existing SAT algorithms. Finally, we provide a set of practical applications of the sat...
Engineering and Analysis of Fixed Priority Schedulers
 IEEE Transactions on Software Engineering
, 1993
"... Scheduling theory holds great promise as a means to a priori validate timing correctness of realtime applications. However, there currently exists a wide gap between scheduling theory and its implementation in operating system kernels running on specific hardware platforms. The implementation of an ..."
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Cited by 77 (8 self)
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Scheduling theory holds great promise as a means to a priori validate timing correctness of realtime applications. However, there currently exists a wide gap between scheduling theory and its implementation in operating system kernels running on specific hardware platforms. The implementation of any particular scheduling algorithm introduces overheadand blocking components which must be accounted for in the timing correctness validation process. This paper presents a methodology for incorporating the costs of scheduler implementation within the context of fixed priority scheduling algorithms. Both eventdriven and timerdriven scheduling implementations are analyzed. We show that for the timerdriven scheduling implementations the selection of the timer interrupt rate can dramatically affect the schedulability of a task set, and we present a method for determining the optimal timer rate. We analyzed both randomly generated and two well defined task sets and found that their schedulabil...
Scheduling Hard RealTime Systems: A Review
, 1991
"... Recent results in the application of... this paper. The review takes the form of an analysis of the problems presented by different application requirements and characteristics. Issues covered include uniprocessor and multiprocessor systems, periodic and aperiodic processes, static and dynamic algor ..."
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Cited by 48 (7 self)
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Recent results in the application of... this paper. The review takes the form of an analysis of the problems presented by different application requirements and characteristics. Issues covered include uniprocessor and multiprocessor systems, periodic and aperiodic processes, static and dynamic algorithms, transient overloads and resource usage. Protocols that limit and reduce blocking are discussed. Considerations are also given to scheduling Ada tasks.
A Systematic Approach to Designing Distributed RealTime Systems
 IEEE Computer
, 1995
"... ions 155 two request entries to exist in multiple queues. For example, in a duallink network two requests can exist simultaneously in multiple station queues [2]. A system is said to be consistent if and only if the order of the same entries in different station queues is consistent with each othe ..."
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Cited by 32 (0 self)
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ions 155 two request entries to exist in multiple queues. For example, in a duallink network two requests can exist simultaneously in multiple station queues [2]. A system is said to be consistent if and only if the order of the same entries in different station queues is consistent with each other. For example, in a duallink network, if request R 1 and request R 2 both exist in queue Q a and queue Q b , and if R 1 is ahead of R 2 in Q a , then R 1 must also be ahead of R 2 in Q b . The inconsistency problem can lead to conflicts between distributed scheduling actions. Inconsistency can be avoided by the following rule: A station is not permitted to enter its request in its own queue until it has successfully made the request on the link. This makes the entries in each queue consistent with the ordering of requests on the link. Therefore, all the queues will be consistent with each other. In the above example, station S b cannot enter its request in its queue until it can make a r...
realtime scheduling: the deadlinemonotonic approach
 in Proc. IEEE Workshop on RealTime Operating Systems and Software
, 1991
"... ABSTRACT. The scheduling of processes to meet deadlines is a difficult problem often simplified by placing severe restrictions upon the timing characteristics of individual processes. One restriction often introduced is that processes must have deadline equal to period. This paper investigates sched ..."
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Cited by 23 (1 self)
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ABSTRACT. The scheduling of processes to meet deadlines is a difficult problem often simplified by placing severe restrictions upon the timing characteristics of individual processes. One restriction often introduced is that processes must have deadline equal to period. This paper investigates schedulability tests for sets of periodic processes whose deadlines are permitted to be less than their period. Such a relaxation enables sporadic processes to be directly incorporated without alteration to the process model. Following an introduction outlining the constraints associated with existing scheduling approaches and associated schedulability tests, the deadlinemonotonic approach is introduced. New schedulability tests are derived which vary in computational complexity. The tests are shown to be directly applicable to the scheduling of sporadic processes.
RealTime System Scheduling
, 1990
"... Recent results in the application of scheduling theory to dependable realtime systems are reviewed. The review takes the form of an analysis of the problems presented by different application requirements and characteristics. Issues covered include uniprocessor and multiprocessor systems, periodic ..."
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Cited by 19 (0 self)
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Recent results in the application of scheduling theory to dependable realtime systems are reviewed. The review takes the form of an analysis of the problems presented by different application requirements and characteristics. Issues covered include uniprocessor and multiprocessor systems, periodic and aperiodic processes, static and dynamic algorithms, transient overloads and resource usage. Protocols that bound and reduce blocking are discussed. A review of specific realtime kernels is also included.
Predictability And Consistency In Realtime Transaction Processing
, 1995
"... A realtime database system (RTDBS) can be defined as a database system where transactions are associated with realtime constraints typically in the form of deadlines. The system must process transactions so as to both meet the deadlines and maintain the data consistency. Previous research effort i ..."
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Cited by 15 (4 self)
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A realtime database system (RTDBS) can be defined as a database system where transactions are associated with realtime constraints typically in the form of deadlines. The system must process transactions so as to both meet the deadlines and maintain the data consistency. Previous research effort in this field has been focused on scheduling transactions with soft or firm deadlines under the conventional transaction model and database system architecture which cannot support predictable real#time transaction processing. In this thesis, we provide a framework to realize predictable realtime transaction processing, satisfying both timing and consistency constraints of a realtime database system. First, we classify data objects and transactions found in typical realtime database applications, considering their distinct characteristics and requirements. Each type of realtime data objects has its own correctness criteria, different from the conventional one. Real#time transactions a...
Predictability and Consistency in RealTime Database Systems
 Advances in RealTime Systems
, 1993
"... Introduction As our society becomes more integrated with computer technology, information processing for human activities necessitates computing that responds to requests in realtime rather than just with besteffort . Many computer systems are now used to monitor and control physical devices and ..."
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Cited by 15 (1 self)
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Introduction As our society becomes more integrated with computer technology, information processing for human activities necessitates computing that responds to requests in realtime rather than just with besteffort . Many computer systems are now used to monitor and control physical devices and large complex systems which must have predictable and timely behaviors. We call such systems realtime systems. Some realtime systems must maintain and manipulate data shared by many tasks; thus they need to have databases which can provide the services needed by realtime computations. Realtime database systems (RTDBS) have (at least some) transactions with explicit timing constraints, such as deadlines and temporal distances. RTDBS are becoming increasingly important in a wide range of applications, such as aerospace and weapon systems, computerintegrated manufacturing, robotics, nuclear power Sec. 21.2 Characteristics a
Design and Implementation of MarutiII
, 1994
"... this report are those of the author(s) and should not be interpreted as representing the official policies, either expressed or implied, of the Advanced Research Projects Agency, PL, or the U.S. government. References ..."
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Cited by 11 (4 self)
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this report are those of the author(s) and should not be interpreted as representing the official policies, either expressed or implied, of the Advanced Research Projects Agency, PL, or the U.S. government. References
Algorithms for Combinatorial Optimization in Real Time and their Automated Refinement by Genetic Programming
 University of Illinois at UrbanaChampaign
, 1994
"... The goal of this research is to develop a systematic, integrated method of designing efficient search algorithms that solve optimization problems in real time. Search algorithms studied in this thesis comprise metacontrol and primitive search. The class of optimization problems addressed are called ..."
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Cited by 7 (1 self)
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The goal of this research is to develop a systematic, integrated method of designing efficient search algorithms that solve optimization problems in real time. Search algorithms studied in this thesis comprise metacontrol and primitive search. The class of optimization problems addressed are called combinatorial optimization problems, examples of which include many NPhard scheduling and planning problems, and problems in operations research and artificialintelligence applications. The problems we have addressed have a welldefined problem objective and a finite set of welldefined problem constraints. In this research, we use statespace trees as problem representations. The approach we have undertaken in designing efficient search algorithms is an engineering approach and consists of two phases: (a) designing generic search algorithms, and (b) improving by geneticsbased machine learning methods parametric heuristics used in the search algorithms designed. Our approach is a systematic method that integrates domain knowledge, search techniques, and automated learning techniques for designing better search algorithms. Knowledge captured in designing one search algorithm can be carried over for designing new ones. iv ACKNOWLEDGEMENTS I express my sincere gratitude to all the people who have helped me in the course of my graduate study. My thesis advisor, Professor Benjamin W. Wah, was always available for discussions and encouraged me to explore new ideas. I am deeply grateful to the committee