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Approximate Signal Processing
, 1997
"... It is increasingly important to structure signal processing algorithms and systems to allow for trading off between the accuracy of results and the utilization of resources in their implementation. In any particular context, there are typically a variety of heuristic approaches to managing these tra ..."
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Cited by 510 (2 self)
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It is increasingly important to structure signal processing algorithms and systems to allow for trading off between the accuracy of results and the utilization of resources in their implementation. In any particular context, there are typically a variety of heuristic approaches to managing these tradeoffs. One of the objectives of this paper is to suggest that there is the potential for developing a more formal approach, including utilizing current research in Computer Science on Approximate Processing and one of its central concepts, Incremental Refinement. Toward this end, we first summarize a number of ideas and approaches to approximate processing as currently being formulated in the computer science community. We then present four examples of signal processing algorithms/systems that are structured with these goals in mind. These examples may be viewed as partial inroads toward the ultimate objective of developing, within the context of signal processing design and implementation,...
Algorithms for scheduling imprecise computations
 IEEE Computer
, 1991
"... n a hard realtime cyctem, every timeT critical task must meet its timing con1 straint, typically specified as its deadline. (A task is a granule of computation treated by the scheduler as a unit of work to be allocated processor time, or scheduled.) If any timecritical task fails to complete an ..."
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Cited by 257 (17 self)
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n a hard realtime cyctem, every timeT critical task must meet its timing con1 straint, typically specified as its deadline. (A task is a granule of computation treated by the scheduler as a unit of work to be allocated processor time, or scheduled.) If any timecritical task fails to complete and produce its result by its deadline, a timing fault occurs and the task's result is of little or no use. Such factors as variations in the processing times of dynamic algorithms make meeting all deadlines at all times difficult. The imprecise computation te~hniquel~ can minimize this difficulty. It prevents timing faults and achieves graceful degradation by giving the user an approximate result of acceptable quality whenever the system cannot produce the exact result in time. Image processing and tracking are examples of realtime applications where the user may accept timely approximate results: Frames of fuzzy images and rough estimates of location produced in time may be better than perfect images and accurate location data produced too late. In this article, we review workload models that quantify the tradeoff between result quality andcomputation time. We also describe scheduling algorithms that exploit this tradeoff.
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 91 (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...
Anytime Deduction for Probabilistic Logic
 Artif. Intell
, 1994
"... This paper proposes and investigates an approach to deduction in probabilistic logic, using as its medium a language that generalizes the propositional version of Nilsson's probabilistic logic by incorporating conditional probabilities. Unlike many other approaches to deduction in probabilistic ..."
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Cited by 68 (1 self)
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This paper proposes and investigates an approach to deduction in probabilistic logic, using as its medium a language that generalizes the propositional version of Nilsson's probabilistic logic by incorporating conditional probabilities. Unlike many other approaches to deduction in probabilistic logic, this approach is based on inference rules and therefore can produce proofs to explain how conclusions are drawn. We show how these rules can be incorporated into an anytime deduction procedure that proceeds by computing increasingly narrow probability intervals that contain the tightest entailed probability interval. Since the procedure can be stopped at any time to yield partial information concerning the probability range of any entailed sentence, one can make a tradeoff between precision and computation time. The deduction method presented here contrasts with other methods whose ability to perform logical reasoning is either limited or requires finding all truth assignments consistent ...
Resource reservation in dynamic realtime systems
 RealTime Systems
, 2004
"... Abstract. This paper focuses on the problem of providing ef®cient runtime support to multimedia applications in a realtime system, where different types of tasks (characterized by different criticality) can coexist.Whereas critical realtime tasks (hard tasks) are guaranteed based on worstcase ex ..."
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Cited by 58 (13 self)
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Abstract. This paper focuses on the problem of providing ef®cient runtime support to multimedia applications in a realtime system, where different types of tasks (characterized by different criticality) can coexist.Whereas critical realtime tasks (hard tasks) are guaranteed based on worstcase execution times and minimum interarrival times, multimedia tasks are served based on mean parameters.A novel bandwidth reservation mechanism (the constant bandwidth server) allows realtime tasks to execute in a dynamic environment under a temporal protection mechanism, so that each task will never exceed a prede®ned bandwidth, independently of its actual requests.The paper also discusses how the proposed server can be used for handling aperiodic tasks ef®ciently and how a statistical analysis can be applied to perform a probabilistic guarantee of soft tasks.The performance of the proposed method is compared with that of similar service mechanisms (dynamic realtime servers and proportional share schedulers) through extensive simulation experiments.
Aperiodic Task Scheduling for RealTime Systems
, 1990
"... This thesis develops the Sporadic Server (SS) algorithm for scheduling aperiodic tasks in realtime systems. The SS algorithm is an extension of the rate monotonic algorithm which was designed to schedule periodic tasks. This thesis demonstrates that the SS algorithm is able to guarantee deadlines f ..."
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Cited by 51 (0 self)
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This thesis develops the Sporadic Server (SS) algorithm for scheduling aperiodic tasks in realtime systems. The SS algorithm is an extension of the rate monotonic algorithm which was designed to schedule periodic tasks. This thesis demonstrates that the SS algorithm is able to guarantee deadlines for harddeadline aperiodic tasks and provide good responsiveness for softdeadline aperiodic tasks while avoiding the schedulability penalty and implementation complexity of previous aperiodic service algorithms. It is also proven that the aperiodic servers created by the SS algorithm can be treated as equivalentlysized periodic tasks when assessing schedulability. This allows all the scheduling theories developed for the rate monotonic algorithm to be used to schedule aperiodic tasks. For scheduling aperiodic and periodic tasks that share data, this thesis defines the interactions and schedulability impact of using the SS algorithm with the priority inheritance protocols. For scheduling ha...
The Challenges of RealTime AI
 IEEE Computer
, 1995
"... This paper describes an organizing conceptual structure for current realtime AI research, clarifying the different meanings this term has acquired for various researchers ..."
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Cited by 36 (6 self)
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This paper describes an organizing conceptual structure for current realtime AI research, clarifying the different meanings this term has acquired for various researchers
Tight Performance Bounds of Heuristics for a RealTime Scheduling Problem
, 1993
"... The problem of scheduling a set of periodic tasks on a number of processors using a fixedpriority assignment scheme was first studied by Dhall and Liu in their paper entitled "On a realtime scheduling problem". Two scheduling heuristics ¾ RateMonotonicNextFit (RMNF) and RateMonotonic ..."
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Cited by 21 (2 self)
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The problem of scheduling a set of periodic tasks on a number of processors using a fixedpriority assignment scheme was first studied by Dhall and Liu in their paper entitled "On a realtime scheduling problem". Two scheduling heuristics ¾ RateMonotonicNextFit (RMNF) and RateMonotonic FirstFit (RMFF) were proposed, and their worstcase performance was proven to have an upper bound of 2.67 and 2.2, and a lower bound of 2.4 and 2.0, respectively. In this paper, we first tighten up the worstcase bounds for both RMNF and RMFF, and at the same time, correct some errors existing in the original proof of the upper bound for RMFF. The tight worstcast bounds of RMNF and RMFF are proven to be 2.67 and 2.33, respectively. Then, in an effort to find a more efficient algorithm, we propose a new scheduling heuristic ¾ RateMonotonicBestFit (RMBF), and study its worstcase performance. Surprisingly, RMBF also has a tight worst case bound of 2.33. I. Introduction The problem of preemptivel...
An Introduction to Control and Scheduling
 39TH IEEE CONFERENCE ON DECISION AND CONTROL
, 1999
"... The report gives a stateoftheart survey of the field of integrated control and scheduling. Subtopics discussed are implementation and scheduling of periodic control loops, scheduling under overload, control and scheduling codesign, dynamic task adaptation, feedback scheduling, and scheduling o ..."
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Cited by 20 (6 self)
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The report gives a stateoftheart survey of the field of integrated control and scheduling. Subtopics discussed are implementation and scheduling of periodic control loops, scheduling under overload, control and scheduling codesign, dynamic task adaptation, feedback scheduling, and scheduling of imprecise calculations. The report also presents the background, motivation, and research topics in the ARTES project “Integrated