## Enhancing the Performance and Dependability of Real-Time Systems (1995)

Venue: | IN PROCEEDINGS OF THE IEEE INTERNATIONAL COMPUTER PERFORMANCE AND DEPENDABILILITY SYMPOSIUM |

Citations: | 6 - 3 self |

### BibTeX

@INPROCEEDINGS{Hull95enhancingthe,

author = {D. L. Hull and W. Feng and J. W. -s. Liu},

title = {Enhancing the Performance and Dependability of Real-Time Systems},

booktitle = {IN PROCEEDINGS OF THE IEEE INTERNATIONAL COMPUTER PERFORMANCE AND DEPENDABILILITY SYMPOSIUM},

year = {1995},

pages = {174--182},

publisher = {}

}

### OpenURL

### Abstract

The imprecise-computation technique was proposed as a way to handle transient overloads and enhance the dependability of real-time systems. In a system based on this technique, each time-critical task produces an approximate but usable result whenever a failure or overload prevents the system from producing a precise result. This approach makes meeting deadlines easier, increases the availability of data and services, reduces the need for error-recovery operations, and minimizes the costs in replication. In this paper, we provide an overview of ways to implement and schedule imprecise computations. We then describe the Imprecise Computation Server (ICS) and how it is used to ensure real-time performance of time-critical applications.

### Citations

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Citation Context ...o recovery action is needed if the result allows the system to maintain track of the targets. In embedded systems, this technique can be used with traditional checkpointing and replication techniques =-=[9, 15]-=-. The result is a reduction of the costs for providing fault tolerance and enhanced availability. After describing ways to implement imprecise computations, we provide an overview on methods to schedu... |

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Citation Context ...he state saved by the last checkpoint operation and resumes its execution from that state. 5.2 Implementation The Imprecise Computation Server (ICS) is implemented on top of the Mach operating system =-=[1]-=-. It makes use of IMIG, a modified version of the Mach Interface Generator (MIG) [13]. Handler Caller Supervisor Callee Client Server Scheduler Figure 1: An imprecise computation server and its client... |

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Citation Context ...of tasks fT i g with identical weights is max i f(o i \Gammaoe i )=o i g. Polynomial-time algorithms for finding optimal schedules with the smallest maximum fraction of discarded work can be found in =-=[6, 17]-=-. On the other hand, the result of a task may improve in quality at a faster as it executes longer. The optional part of such a task should be scheduled as much as possible or not at all. Hence, the e... |

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Citation Context ...tal) algorithms, including all iterative algorithms, statistical detection and estimation, incremental voice and video transmissions [14], incremental query processing [21], and AI anytime algorithms =-=[2]-=-. In particular, a task based on an anytime algorithm is either entirely optional or has a mandatory portion that takes a negligible amount of time to complete compared with the rest of the task. Not ... |

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Citation Context ...tasks impact the overall quality of the result produced by all the tasks in the system. Examples of optimal and suboptimal algorithms which minimize the total amount of discarded work can be found in =-=[3, 18, 19]-=-. The qualities of results produced by some tasks (e.g., those based on most iterative algorithms and statistical methods) improve faster during the early part of their execution, and the rates of imp... |

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Citation Context ...e to the extensive computations involved in satisfying complex geometric constraints. A possible solution would be to restrict the power of the constraint solver by employing propagational algorithms =-=[5]-=- whose implementation can be simplified with ICS. Radar tracking is another real-time application which would benefit from ICS. In this application, the mandatory part consists of processing the retur... |

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Citation Context ...are monotone (or simply incremental) algorithms, including all iterative algorithms, statistical detection and estimation, incremental voice and video transmissions [14], incremental query processing =-=[21]-=-, and AI anytime algorithms [2]. In particular, a task based on an anytime algorithm is either entirely optional or has a mandatory portion that takes a negligible amount of time to complete compared ... |

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36 |
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Citation Context ...tasks impact the overall quality of the result produced by all the tasks in the system. Examples of optimal and suboptimal algorithms which minimize the total amount of discarded work can be found in =-=[3, 18, 19]-=-. The qualities of results produced by some tasks (e.g., those based on most iterative algorithms and statistical methods) improve faster during the early part of their execution, and the rates of imp... |

30 | J.A.: Inferring graphical constraints with Rockit
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Citation Context ...s call to the service stub routine. Many real-time applications can benefit from using ICS by taking advantage of the services that it offers. For example, in constraint-based graphics such as Rockit =-=[8]-=-, GITS [16], and Oak [20], the constraint solver must be fast enough to produce interactive response. Specifically, it must be fast enough for constrained visual objects (e.g., two lines constrained t... |

21 |
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Citation Context ...the service stub routine. Many real-time applications can benefit from using ICS by taking advantage of the services that it offers. For example, in constraint-based graphics such as Rockit [8], GITS =-=[16]-=-, and Oak [20], the constraint solver must be fast enough to produce interactive response. Specifically, it must be fast enough for constrained visual objects (e.g., two lines constrained to be perpen... |

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Citation Context ...o recovery action is needed if the result allows the system to maintain track of the targets. In embedded systems, this technique can be used with traditional checkpointing and replication techniques =-=[9, 15]-=-. The result is a reduction of the costs for providing fault tolerance and enhanced availability. After describing ways to implement imprecise computations, we provide an overview on methods to schedu... |

10 |
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Citation Context ...of tasks fT i g with identical weights is max i f(o i \Gammaoe i )=o i g. Polynomial-time algorithms for finding optimal schedules with the smallest maximum fraction of discarded work can be found in =-=[6, 17]-=-. On the other hand, the result of a task may improve in quality at a faster as it executes longer. The optional part of such a task should be scheduled as much as possible or not at all. Hence, the e... |

7 |
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Citation Context ...constraint. From a scheduling point of view, a task with two versions is a mandatory task followed by one with this constraint. Algorithms for scheduling tasks with the 0/1 constraint can be found in =-=[7, 19]-=-. All the aforementioned scheduling algorithms assume that the inputs of the tasks are precise and that the release times and deadlines of individual tasks are given. In many applications, however, th... |

6 | Algorithms for Scheduling Tasks with Input Error and End-to-End deadlines
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(Show Context)
Citation Context ...ts and makes the problem of scheduling imprecise computations more difficult. Several heuristic algorithms for scheduling tasks with imprecise inputs and end-to-end timing constraints can be found in =-=[4]-=-. These algorithms deal with composite tasks, each of which is a chain of component tasks. The composite tasks are independent of each other. The ready time of a composite task is the ready time of it... |

4 |
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Citation Context ...ub routine. Many real-time applications can benefit from using ICS by taking advantage of the services that it offers. For example, in constraint-based graphics such as Rockit [8], GITS [16], and Oak =-=[20]-=-, the constraint solver must be fast enough to produce interactive response. Specifically, it must be fast enough for constrained visual objects (e.g., two lines constrained to be perpendicular to one... |

3 | A position paper for the 1987 IEEE workshop on realtime operating systems - Liu, Lin, et al. - 1987 |

1 |
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(Show Context)
Citation Context ...d. It is applicable whenever there are monotone (or simply incremental) algorithms, including all iterative algorithms, statistical detection and estimation, incremental voice and video transmissions =-=[14]-=-, incremental query processing [21], and AI anytime algorithms [2]. In particular, a task based on an anytime algorithm is either entirely optional or has a mandatory portion that takes a negligible a... |