Handling Overruns and Underruns of Real-Time Processes With Precedence and Exclusion Relations Using a Pre-Run-Time Schedule

2013 ◽  
Author(s):  
Jia Xu
Keyword(s):  
Real Time ◽  
Computation Time ◽  
Total System ◽  
Time Process ◽  
Time Schedule ◽  
Worst Case ◽  
Processor Time ◽  
The Real ◽  
Actual Computation ◽  
Run Time

Many embedded systems applications have hard timing requirements where real-time processes with precedence and exclusion relations must be completed before specified deadlines. This requires that the worst-case computation times of the real-time processes be estimated with sufficient precision during system design, which sometimes can be difficult in practice. If the actual computation time of a real-time process during run-time exceeds the estimated worst-case computation time, an overrun will occur, which may cause the real-time process to not only miss its own deadline, but also cause a cascade of other real-time processes to also miss their deadline, possibly resulting in total system failure. However, if the actual computation time of a real-time process during run-time is less than the estimated worst-case computation time, an underrun will occur, which may result in under-utilization of system resources. This paper describes a method for handling underruns and overruns when scheduling a set of real-time processes with precedence and exclusion relations using a pre-run-time schedule. The technique effectively tracks and utilizes unused processor time resources to reduce the chances of missing real-time process deadlines, thereby providing the capability to significantly increase both system utilization and system robustness in the presence of inaccurate estimates of the worst-case computation times of real-time processes.

A Method for Simultaneously Satisfying Important Constraints and Dependencies for Many Different Types of Processes in Embedded Real-Time Systems

2011 ◽  
Author(s):  
Jia Xu
Keyword(s):  
Real Time ◽  
Computation Time ◽  
Real Time Systems ◽  
Worst Case ◽  
Release Times ◽  
Different Types ◽  
High Assurance ◽  
Run Time ◽  
Soft Deadline ◽  
Time Systems

In most embedded, real-time applications, processes need to satisfy various important constraints and dependencies, such as release times, offsets, precedence relations, and exclusion relations. Embedded, real-time systems with high assurance requirements often must execute many different types of processes with such constraints and dependencies. Some of the processes may be periodic and some of them may be asynchronous. Some of the processes may have hard deadlines and some of them may have soft deadlines. For some of the processes, especially the hard real-time processes, complete knowledge about their characteristics can and must be acquired before run-time. For other processes, prior knowledge of their worst case computation time and their data requirements may not be available. It is important for many embedded real-time systems to be able to simultaneously satisfy as many important constraints and dependencies as possible for as many different types of processes as possible. In this paper, we discuss what types of important constraints and dependencies can be satisfied among what types of processes. We also present a method which guarantees that, for every process, no matter whether it is periodic or asynchronous, and no matter whether it has a hard deadline or a soft deadline, as long as the characteristics of that process are known before run-time, then that process will be guaranteed to be completed before predetermined time limits, while simultaneously satisfying many important constraints and dependencies with other processes.

Efficiently Handling Process Overruns and Underruns in Real-Time Embedded Systems

2015 ◽  
Author(s):  
Jia Xu
Keyword(s):  
Embedded Systems ◽  
Real Time ◽  
Time Process ◽  
Time System ◽  
Worst Case ◽  
Real Time System ◽  
System Utilization ◽  
System Overhead ◽  
Run Time

Methods for handling process underruns and overruns when scheduling a set of real-time processes increase both system utilization and robustness in the presence of inaccurate estimates of the worst-case computations of real-time processes. In this paper, we present a method that efficiently re-computes latest start times for real time processes during run-time in the event that a real-time process is preempted or has completed (or overrun). The method effectively identifies which process latest start times will be affected by the preemption or completion of a process. Hence the method is able to effectively reduce real-time system overhead by selectively re-computing latest start times for the specific processes whose latest start times are changed by a process preemption or completion, as opposed to indiscriminately re-computing latest start times for all the processes.

scholarly journals A new algorithm for considering green communication and excellent sensing performance in cognitive radio networks

2020 ◽  
Vol 16 (6) ◽  
pp. 155014772093313 ◽  
Author(s):  
Tangsen Huang ◽  
Xiangdong Yin ◽  
Qingjiao Cao
Keyword(s):  
Real Time ◽  
Spectrum Sensing ◽  
Computation Time ◽  
Time Spectrum ◽  
Fusion Center ◽  
Local Data ◽  
Green Communication ◽  
Processing Efficiency ◽  
The Real ◽  
Sensing Performance

Multi-node cooperative sensing can effectively improve the performance of spectrum sensing. Multi-node cooperation will generate a large number of local data, and each node will send its own sensing data to the fusion center. The fusion center will fuse the local sensing results and make a global decision. Therefore, the more nodes, the more data, when the number of nodes is large, the global decision will be delayed. In order to achieve the real-time spectrum sensing, the fusion center needs to quickly fuse the data of each node. In this article, a fast algorithm of big data fusion is proposed to improve the real-time performance of the global decision. The algorithm improves the computing speed by reducing repeated computation. The reinforcement learning mechanism is used to mark the processed data. When the same environment parameter appears, the fusion center can directly call the nodes under the parameter environment, without having to conduct the sensing operation again. This greatly reduces the amount of data processed and improves the data processing efficiency of the fusion center. Experimental results show that the algorithm in this article can reduce the computation time while improving the sensing performance.

Cleaning Display Cases Dusting or Polishing our Challenges?

Collections ◽  
2009 ◽  
Vol 5 (1) ◽  
pp. 73-86
Author(s):  
Aristotelis Georgios Sakellariou
Keyword(s):  
Real Time ◽  
Time Process ◽  
Visitor Experience ◽  
The Real ◽  
Large Display ◽  
Visual Access ◽  
Mixed Collection ◽  
Of Greece ◽  
Jewish Museum

This article introduces the reader to the considerations that had to be taken when cleaning and refreshing two of its large display cases at the Jewish Museum of Greece. Those display cases contain a mixed collection of variable items namely costumes, photographs, prints and wa-tercolours. The staff of the museum planned in advance, ensuring the safety of the objects and staff. Eventually it is natural for unpredicted problems to occur in the real time process. The Museum acknowledged the convenience of the visitor pathway and, moreover, granted visual access to the treatment actions by encouraging communication with the working staff, enriching the visitor experience. Finally the process was beneficial for evaluating the staff's teamwork and the production of a record, and a methodology to be followed for other display cases of the museum and potentially by other institutions.

A Classifier of Shoulder Movements for a Wearable EMG-Based Device

2017 ◽  
Vol 02 (02) ◽  
pp. 1740003
Author(s):  
Giuseppina Gini ◽  
Lisa Mazzon ◽  
Simone Pontiggia ◽  
Paolo Belluco
Keyword(s):  
Real Time ◽  
Computation Time ◽  
Body Part ◽  
Time Constraints ◽  
Pattern Recognition Method ◽  
Noninvasive Method ◽  
Recognition Method ◽  
Two Phase ◽  
The Real ◽  
User Intentions

Prostheses and exoskeletons need a control system able to rapidly understand user intentions; a noninvasive method is to deploy a myoelectric system, and a pattern recognition method to classify the intended movement to input to the controller. Here we focus on the classification phase. Our first aim is to recognize nine movements of the shoulder, a body part seldom considered in the literature and difficult to treat since the muscles involved are deep. We show that our novel sEMG two-phase classifier, working on a signal window of 500[Formula: see text]ms with 62[Formula: see text]ms increment, has a 97.7% accuracy for nine movements and about 100% accuracy on five movements. After developing the classifier using professionally collected sEMG data from eight channels, our second aim is to implement the classifier on a wearable device, composed by the Intel Edison board and a three-channel experimental portable acquisition board. Our final aim is to develop a complete classifier for dynamic situations, considering the transitions between movements and the real-time constraints. The performance of the classifier, using three channels, is about 96.9%, the classification frequency is 62[Formula: see text]Hz, and the computation time is 16[Formula: see text]ms, far less than the real-time constraint of 300[Formula: see text]ms.

Implementation of Embedded Linux Systems on FPGA Based Circuits for Real Time Process Control

MACRo 2015 ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 145-154 ◽  
Author(s):  
Szabolcs Hajdu ◽  
Sándor-Tihamér Brassai
Keyword(s):  
Operating System ◽  
Process Control ◽  
Real Time ◽  
Data Exchange ◽  
Control Unit ◽  
Control Algorithms ◽  
Time Process ◽  
The Real ◽  
Measurement Results ◽  
Embedded Soc

AbstractThis paper presents a framework based on embedded SOC systems, which allows the testing and use of control algorithms implemented on FPGA circuits. For monitoring and parameterization a real-time Linux operating system was used. In this paper different methods for data exchange between the operating system and the control unit were introduced. The delay between the operating system and the control unit during the data exchange was studied and the measurement results discussed reflect the real-time functionality of the system.

Efficiently Handling Process Overruns and Underruns on Multiprocessors in Real-Time Embedded Systems

2017 ◽  
Author(s):  
Jia Xu
Keyword(s):  
Embedded Systems ◽  
Real Time ◽  
Time Complexity ◽  
Multiprocessor System ◽  
Multiprocessor Systems ◽  
Worst Case ◽  
Real World Applications ◽  
Run Time ◽  
Hard Real Time ◽  
Time Overhead

In hard real-time and embedded multiprocessor system real-world applications, it is very important to strive to minimize the run-time overhead of the scheduler as much as possible, especially in hard real-time and embedded multiprocessor systems with limited processor and system resources. In this paper, we present a method that reduces the worst-case time complexity of the run-time scheduler for re-computing latest start times and for selecting processes for execution on a multiprocessor at run-time to O(n), where n is the number of processes.

A WCET Test Method Based on Associative Process Communication

2014 ◽  
Vol 577 ◽  
pp. 865-872
Author(s):  
Jun Yi Li ◽  
Yi Zhang ◽  
Ren Fa Li
Keyword(s):  
Real Time ◽  
Test Method ◽  
Basic Block ◽  
Worst Case ◽  
Real Time System ◽  
The Real ◽  
Process Communication ◽  
Associative Process ◽  
Worst Case Execution Time ◽  
Time Requirements

The Real-time system estimates the worst-case execution time (WCET) of the program to ensure the real-time requirements of the system. In this paper, a test method based on Associative Process Communication (APC) is put forward. First it tests the WCET value of basic blocks of ICFG through the use of APC algorithm, and then estimates the WCET by analyzing the worst execution path of the basic block. APC test method tests all benchmarks of Mälardalen. And the test results show that the proposed test method is precise and effective, and the test error is within the theoretical analysis.

Research on Network Partitioning Based on Expanded Grey Cluster Theory

2013 ◽  
Vol 791-793 ◽  
pp. 1690-1694
Author(s):  
Ya Ning Shao ◽  
Bo Wang ◽  
Di Chen Liu
Keyword(s):  
Parallel Computing ◽  
Real Time ◽  
Voltage Stability ◽  
Short Circuit ◽  
Computation Time ◽  
Cluster Method ◽  
Network Partitioning ◽  
Cluster Theory ◽  
The Real ◽  
Identification Criterion

the voltage stability discriminant method of short circuit capacity indicators based on measured trajectory needs a great deal of computation time while dynamic Thevenin equivalent need to be done to all the nodes, it is unable to meet the requirements of rapid real-time sentenced to stability. On this foundation, this paper proposes a quick network partitioning method. Firstly, start the real-time disturbance identification criterion and pick up the bus nods triggered by the disturbance. Then split the bus nods into k subsets using Expanded Grey Cluster method. Finally evaluate stability by parallel computing. The method is proved simple, efficient and practical through simulation.

IMPROVED COMPETITIVE ALGORITHMS FOR TWO-PROCESSOR REAL-TIME SYSTEMS

2004 ◽  
Vol 15 (05) ◽  
pp. 733-751 ◽  
Author(s):  
JOSEPH Y.-T. LEUNG
Keyword(s):  
Real Time ◽  
Computation Time ◽  
Real Time Systems ◽  
Worst Case ◽  
Computing Power ◽  
Migration Model ◽  
A Value ◽  
On Line ◽  
Time Systems ◽  
Competitive Algorithms

The problem of competitive on-line scheduling in two-processor real-time environments is studied. The model of Koren and Shasha is followed: Every task has a deadline and a value that it obtains only if it completes by its deadline – the value being its computation time. The goal is to design on-line schedulers with worst-case guarantees compared with a clairvoyant scheduler. Koren and Shasha gave algorithms for the migration and no-migration models, with competitive multipliers of 2 and 3, respectively. In this article, we give an algorithm for the no-migration model with an improved competitive multiplier of [Formula: see text]. We also show that the competitive multiplier for the migration model can be lowered by using a fast processor and a slow processor, compared with using several parallel and identical processors with the same aggregate computing power.

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