| 1. |
- Abdullah, Jakaria, et al.
(författare)
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Towards a Tool : TIMES-Pro for Modeling, Analysis, Simulation and Implementation of Cyber-Physical Systems
- 2017
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Ingår i: MODELS, ALGORITHMS, LOGICS AND TOOLS. - Cham : SPRINGER INTERNATIONAL PUBLISHING AG. - 9783319631219 - 9783319631202 ; , s. 623-639
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Konferensbidrag (refereegranskat)abstract
- We consider a Cyber-Physical System (CPS) as a network of components that are either physical plants with continuous behaviors or discrete controllers. To build CPS's in a systematic manner, the TIMES-Pro tool is designed to support modeling, analysis and code generation for real-time simulation and final deployment. In this paper, we present our decisions in designing the modeling language, the tool architecture and features of TIMES-Pro, and also a case study to demonstrate its applicability.
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| 2. |
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| 3. |
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| 4. |
- Chen, Gang, et al.
(författare)
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EDF-VD Scheduling of Flexible Mixed-Criticality System With Multiple-Shot Transitions
- 2018
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Ingår i: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems. - 0278-0070 .- 1937-4151. ; 37:11, s. 2393-2403
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Tidskriftsartikel (refereegranskat)abstract
- The existing mixed-criticality (MC) real-time task models assume that once any high-criticality task overruns, all high-criticality jobs execute up to their most pessimistic WCET estimations simultaneously in a one-shot manner. This is very pessimistic in the sense of unnecessary resource overbooking. In this paper, we propose a more generalized mixed-critical real-time task model, called flexible MC model with multiple-shot transitions (FMC-MST), to address this problem. In FMC-MST, high-criticality tasks can transit multiple intermediate levels to handle less pessimistic overruns independently and to nonuni-formly scale the deadline on each level. We develop a run-time schedulability analysis for FMC-MST under EDF-VD scheduling, in which a better tradeoff between the penalties of low-criticality tasks and the overruns of high-criticality tasks is achieved to improve the service quality of low-criticality tasks. We also develop a resource optimization technique to find resource-efficient level-insertion configurations for FMC-MST task systems under MC timing constraints. Experiments demonstrate the effectiveness of FMC-MST compared with the state-of-the-art techniques.
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| 5. |
- Chen, Gang, et al.
(författare)
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Utilization-Based Scheduling of Flexible Mixed-Criticality Real-Time Tasks
- 2018
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Ingår i: IEEE Transactions on Computers. - : IEEE COMPUTER SOC. - 0018-9340 .- 1557-9956. ; 67:4, s. 543-558
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Tidskriftsartikel (refereegranskat)abstract
- Mixed-criticality models are an emerging paradigm for the design of real-time systems because of their significantly improved resource efficiency. However, formal mixed-criticality models have traditionally been characterized by two impractical assumptions: once any high-criticality task overruns, all low-criticality tasks are suspended and all other high-criticality tasks are assumed to exhibit high-criticality behaviors at the same time. In this paper, we propose a more realistic mixed-criticality model, called the flexible mixed-criticality (FMC) model, in which these two issues are addressed in a combined manner. In this new model, only the overrun task itself is assumed to exhibit high-criticality behavior, while other high-criticality tasks remain in the same mode as before. The guaranteed service levels of low-criticality tasks are gracefully degraded with the overruns of high-criticality tasks. We derive a utilization-based technique to analyze the schedulability of this new mixed-criticality model under EDF-VD scheduling. During run time, the proposed test condition serves an important criterion for dynamic service level tuning, by means of which the maximum available execution budget for low-criticality tasks can be directly determined with minimal overhead while guaranteeing mixed-criticality schedulability. Experiments demonstrate the effectiveness of the FMC scheme compared with state-of-the-art techniques.
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| 6. |
- Du, He, et al.
(författare)
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Scope-aware data cache analysis for OpenMP programs on multi-core processors
- 2019
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Ingår i: Journal of systems architecture. - : ELSEVIER. - 1383-7621 .- 1873-6165. ; 98, s. 443-452
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Tidskriftsartikel (refereegranskat)abstract
- OpenMP is the de facto standard parallel programming framework on shared memory architectures, which is not only widely used in general and high-performance computing but also draws increasing interests for real-time embedded systems. Choosing the appropriate assignment of loop iterations to threads is one of the most critical decisions when parallelizing loops, especially considering the large impact by caches behaviors to the program execution time. In this paper, we study data cache analysis for OpenMP programs with parallel loops. We first present a method considering the impact of the schedule clause in OpenMP programs on cache behavior. We capture the dynamic behavior of memory access by computing its temporal scope (the loop iterations where a given memory block is accessed for a given data reference) during address analysis. Based on the ACS representation, we present a temporal scope aware data cache miss calculation technique. Through the experimental result, we propose a convenient way to choose an appropriate parallelization scheme for OpenMP programs.
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| 7. |
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| 8. |
- Feng, Zhiwei, et al.
(författare)
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An Efficient UAV Hijacking Detection Method Using Onboard Inertial Measurement Unit
- 2019
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Ingår i: ACM Transactions on Embedded Computing Systems. - : ASSOC COMPUTING MACHINERY. - 1539-9087 .- 1558-3465. ; 17:6
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Tidskriftsartikel (refereegranskat)abstract
- With the fast growth of civil drones, their security problems meet significant challenges. A commercial drone may be hijacked by a GPS-spoofing attack for illegal activities, such as terrorist attacks. The target of this article is to develop a technique that only uses onboard gyroscopes to determine whether a drone has been hijacked. Ideally, GPS data and the angular velocities measured by gyroscopes can be used to estimate the acceleration of a drone, which can be further compared with the measurement of the accelerometer to detect whether a drone has been hijacked. However, the detection results may not always be accurate due to some calculation and measurement errors, especially when no hijacking occurs in curve trajectory situations. To overcome this, in this article, we propose a novel and simple method to detect hijacking only based on gyroscopes' measurements and GPS data, without using any accelerometer in the detection procedure. The computational complexity of our method is very low, which is suitable to be implemented in the drones with micro-controllers. On the other hand, the proposed method does not rely on any accelerometer to detect attacks, which means it receives less information in the detection procedure and may reduce the results accuracy in some special situations. While the previous method can compensate for this flaw, the high detection results also can be guaranteed by using the above two methods. Experiments with a quad-rotor drone are conducted to show the effectiveness of the proposed method and the combination method.
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| 9. |
- Feng, Zhiwei, et al.
(författare)
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Efficient Drone Hijacking Detection using Onboard Motion Sensors
- 2017
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Ingår i: Proceedings Of The 2017 Design, Automation & Test In Europe Conference & Exhibition (DATE). - : IEEE. - 9783981537093 ; , s. 1414-1419
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Konferensbidrag (refereegranskat)abstract
- The fast growth of civil drones raises significant security challenges. A legitimate drone may be hijacked by GPS spoofing for illegal activities, such as terrorist attacks. The target of this paper is to develop techniques to let drones detect whether they have been hijacked using onboard motion sensors (accelerometers and gyroscopes). Ideally, the linear acceleration and angular velocity measured by motion sensors can be used to estimate the position of a drone, which can be compared with the position reported by GPS to detect whether the drone has been hijacked. However, the position estimation by motion sensors is very inaccurate due to the significant error accumulation over time. In this paper, we propose a novel method to detect hijacking based on motion sensors measurements and GPS, which overcomes the accumulative error problem. The computational complexity of our method is very low, and thus is suitable to be implemented in the micro-controllers of drones. Experiments with a quad-rotor drone are conducted to show the effectiveness of the proposed method.
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| 10. |
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| 11. |
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| 12. |
- Guan, Nan, et al.
(författare)
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Delay analysis of structural real-time workload
- 2015
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Ingår i: Proc. 18th Conference on Design, Automation and Test in Europe. - Piscataway, NJ : IEEE. - 9783981537055 ; , s. 223-228
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Konferensbidrag (refereegranskat)
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| 13. |
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| 14. |
- Guan, Nan, et al.
(författare)
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Scalable timing analysis with refinement
- 2015
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Ingår i: Tools and Algorithms for the Construction and Analysis of Systems. - Berlin, Heidelberg : Springer. - 9783662466803 ; , s. 3-18
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Konferensbidrag (refereegranskat)
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| 15. |
- He, Qingqiang, et al.
(författare)
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On the Consensus Mechanisms of Blockchain/DLT for Internet of Things
- 2018
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Ingår i: 2018 IEEE 13th International Symposium On Industrial Embedded Systems (SIES). - : IEEE. - 9781538641552 ; , s. 150-159
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Konferensbidrag (refereegranskat)abstract
- Internet of Things (IoT) has been experiencing exponential growth in recent years, but still faces many serious challenges. The distributed ledger technology (DLT), e.g., Blockchain, not only appears to be promising to address these technical challenges, but also brings tremendous opportunities for new application and business models. However, the convergence of IoT and DLT is yet a goal far beyond our reach today. Among many problems that have not been sufficiently understood, a fundamental one is how to design appropriate consensus mechanisms for DLT applied to IoT, which is the theme of this paper. We first discuss the potential benefits of applying DLT to IoT, and identify major challenges posed to DLT by IoT. Then we make a survey of existing DLT consensus mechanisms, to summarize major principles and discuss their pros and cons when applied in IoT.
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| 16. |
- Jiang, Xu, et al.
(författare)
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Semi-Federated Scheduling of Parallel Real-Time Tasks on Multiprocessors
- 2017
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Ingår i: 2017 IEEE Real-Time Systems Symposium (RTSS). - : IEEE. - 9781538614143 ; , s. 80-91
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Konferensbidrag (refereegranskat)abstract
- Federated scheduling is a promising approach to schedule parallel real-time tasks on multi-cores, where each heavy task exclusively executes on a number of dedicated processors, while light tasks are treated as sequential sporadic tasks and share the remaining processors. However, federated scheduling suffers resource waste since a heavy task with processing capacity requirement x + is an element of (where x is an integer and 0 < is an element of < 1) needs x+ 1 dedicated processors. In the extreme case, almost half of the processing capacity is wasted. In this paper we propose the semi-federate scheduling approach, which only grants x dedicated processors to a heavy task with processing capacity requirement x+ is an element of, and schedules the remaining is an element of part together with light tasks on shared processors. Experiments with randomly generated task sets show the semi-federated scheduling approach significantly outperforms not only federated scheduling, but also all existing approaches for scheduling parallel real-time tasks on multi-cores.
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| 17. |
- Jin, Xi, et al.
(författare)
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Analyzing multimode wireless sensor networks using the network calculus
- 2015
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Ingår i: Journal of Sensors. - : Hindawi Limited. - 1687-725X .- 1687-7268. ; 2015, s. 851608:1-12
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Tidskriftsartikel (refereegranskat)abstract
- The network calculus is a powerful tool to analyze the performance of wireless sensor networks. But the original network calculus can only model the single-mode wireless sensor network. In this paper, we combine the original network calculus with the multimode model to analyze the maximum delay bound of the flow of interest in the multimode wireless sensor network. There are two combined methods A-MM and N-MM. The method A-MM models the whole network as a multimode component, and the method N-MM models each node as a multimode component. We prove that the maximum delay bound computed by the method A-MM is tighter than or equal to that computed by the method N-MM. Experiments show that our proposed methods can significantly decrease the analytical delay bound comparing with the separate flow analysis method. For the large-scale wireless sensor network with 32 thousands of sensor nodes, our proposed methods can decrease about 70% of the analytical delay bound.
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| 18. |
- Lampka, Kai, 1972-, et al.
(författare)
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Generalized Finitary Real-Time Calculus
- 2017
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Ingår i: IEEE INFOCOM 2017 - IEEE Conference on Computer Communications. - : IEEE. - 9781509053360
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Real-time Calculus (RTC) is a non-stochastic queuing theory to the worst-case performance analysis of distributed real-time systems. Workload as well as resources are modelled as piece-wise linear, pseudo-periodic curves and the system under investigation is modelled as a sequence of algebraic operations over these curves. The memory footprint of computed curves increases exponentially with the sequence of operations and RTC may become computationally infeasible fast. Recently, Finitary RTC has been proposed to counteract this problem. Finitary RTC restricts curves to finite input domains and thereby counteracts the memory demand explosion seen with pseudo periodic curves of common RTC implementations. However, the proof to the correctness of Finitary RTC specifically exploits the operational semantic of the greed processing component (GPC) model and is tied to the maximum busy window size. This is an inherent limitation, which prevents a straight-forward generalization. In this paper, we provide a generalized Finitary RTC that abstracts from the operational semantic of a specific component model and reduces the finite input domains of curves even further. The novel approach allows for faster computations and the extension of the Finitary RTC idea to a much wider range of RTC models.
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| 19. |
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| 20. |
- Liu, Di, et al.
(författare)
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EDF-VD scheduling of mixed-criticality systems with degraded quality guarantees
- 2016
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Ingår i: Proc. 37th Real-Time Systems Symposium. - : IEEE Computer Society. - 9781509053032 ; , s. 35-46
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Konferensbidrag (refereegranskat)abstract
- This paper studies real-time scheduling of mixed-criticality systems where low-criticality tasks are still guaranteed some service in the high-criticality mode, with reduced execution budgets. First, we present a utilization-based schedulability test for such systems under EDF-VD scheduling. Second, we quantify the suboptimality of EDF-VD (with our test condition) in terms of speedup factors. In general, the speedup factor is a function with respect to the ratio between the amount of resource required by different types of tasks in different criticality modes, and reaches 4/3 in the worst case. Furthermore, we show that the proposed utilization-based schedulability test and speedup factor results apply to the elastic mixed-criticality model as well. Experiments show effectiveness of our proposed method and confirm the theoretical suboptimality results.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Sampson, Joshua N., et al.
(författare)
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Analysis of Heritability and Shared Heritability Based on Genome-Wide Association Studies for 13 Cancer Types
- 2015
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Ingår i: Journal of the National Cancer Institute. - : Oxford University Press (OUP). - 0027-8874 .- 1460-2105. ; 107:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Studies of related individuals have consistently demonstrated notable familial aggregation of cancer. We aim to estimate the heritability and genetic correlation attributable to the additive effects of common single-nucleotide polymorphisms (SNPs) for cancer at 13 anatomical sites. Methods: Between 2007 and 2014, the US National Cancer Institute has generated data from genome-wide association studies (GWAS) for 49 492 cancer case patients and 34 131 control patients. We apply novel mixed model methodology (GCTA) to this GWAS data to estimate the heritability of individual cancers, as well as the proportion of heritability attributable to cigarette smoking in smoking-related cancers, and the genetic correlation between pairs of cancers. Results: GWAS heritability was statistically significant at nearly all sites, with the estimates of array-based heritability, h(l)(2), on the liability threshold (LT) scale ranging from 0.05 to 0.38. Estimating the combined heritability of multiple smoking characteristics, we calculate that at least 24% (95% confidence interval [CI] = 14% to 37%) and 7% (95% CI = 4% to 11%) of the heritability for lung and bladder cancer, respectively, can be attributed to genetic determinants of smoking. Most pairs of cancers studied did not show evidence of strong genetic correlation. We found only four pairs of cancers with marginally statistically significant correlations, specifically kidney and testes (rho = 0.73, SE = 0.28), diffuse large B-cell lymphoma (DLBCL) and pediatric osteosarcoma (rho = 0.53, SE = 0.21), DLBCL and chronic lymphocytic leukemia (CLL) (rho = 0.51, SE = 0.18), and bladder and lung (rho = 0.35, SE = 0.14). Correlation analysis also indicates that the genetic architecture of lung cancer differs between a smoking population of European ancestry and a nonsmoking Asian population, allowing for the possibility that the genetic etiology for the same disease can vary by population and environmental exposures. Conclusion: Our results provide important insights into the genetic architecture of cancers and suggest new avenues for investigation.
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| 25. |
- Sun, Jinghao, et al.
(författare)
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A Capacity Augmentation Bound for Real-Time Constrained-Deadline Parallel Tasks Under GEDF
- 2018
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Ingår i: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems. - 0278-0070 .- 1937-4151. ; 37:11, s. 2200-2211
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Tidskriftsartikel (refereegranskat)abstract
- Capacity augmentation bound is a widely used quantitative metric in theoretical studies of schedulability analysis for directed acyclic graph (DAG) parallel real-time tasks, which not only quantifies the suboptimality of the scheduling algorithms, but also serves as a simple linear-time schedulability test. Earlier studies on capacity augmentation bounds of the sporadic DAG task model were either restricted to a single DAG task or a set of tasks with implicit deadlines. In this paper, we consider parallel tasks with constrained deadlines under global earliest deadline first policy. We first show that it is impossible to obtain a constant bound for our problem setting, and derive both lower and upper bounds of the capacity augmentation bound as a function with respect to the maximum ratio of task period to deadline. Our upper bound is at most 1.47 times larger than the optimal one. We conduct experiments to compare the acceptance ratio of our capacity augmentation bound with the existing schedulability test also having linear-time complexity. The results show that our capacity augmentation bound significantly outperforms the existing linear-time schedulability test under different parameter settings.
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| 26. |
- Sun, Jinghao, et al.
(författare)
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Feasibility of fork-join real-time task graph models : Hardness and algorithms
- 2016
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Ingår i: ACM Transactions on Embedded Computing Systems. - : Association for Computing Machinery (ACM). - 1539-9087 .- 1558-3465. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- In the formal analysis of real-time systems, modeling of branching codes and modeling of intratask parallelism structures are two of the most important research topics. These two real-time properties are combined, resulting in the fork-join real-time task (FJRT) model, which extends the digraph-based task model with forking and joining semantics. We prove that the EDF schedulability problem on a preemptive uniprocessor for the FJRT model is coNP-hard in the strong sense, even if the utilization of the task system is bounded by a constant strictly less than 1. Then, we show that the problem becomes tractable with some slight structural restrictions on parallel sections, for which we propose an exact schedulability test with pseudo-polynomial time complexity. Our results thus establish a borderline between the tractable and intractable FJRT models.
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| 27. |
- Sun, Jinghao, et al.
(författare)
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Real-Time Scheduling and Analysis of OpenMP Task Systems with Tied Tasks
- 2017
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Ingår i: 2017 IEEE Real-Time Systems Symposium (RTSS). - : IEEE. - 9781538614143 ; , s. 92-103
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Konferensbidrag (refereegranskat)abstract
- OpenMP is a promising framework for developing parallel real-time software on multi-cores. Although similar to the DAG task model, OpenMP task systems are significantly more difficult to analyze due to constraints posed by the OpenMP specification. An important feature in OpenMP is tied tasks, which must execute on the same thread during the whole life cycle. Although tied tasks enjoy benefits in simplicity and efficiency, it was considered to be not suitable to real-time systems due to its complex behavior. In this paper, we study the real-time scheduling and analysis of OpenMP task systems with tied tasks. First, we show that under the existing scheduling algorithms in OpenMP, tied tasks indeed may lead to extremely bad timing behaviors where the parallel workload is sequentially executed completely. To solve this problem, we proposed a new scheduling algorithm and developed two response time bounds for it, with different trade-off between simplicity and analysis precision. Experiments with both randomly generated OpenMP task systems and realistic OpenMP programs show that the response time bounds obtained by our approach for tied task systems are very close to that of untied tasks.
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| 28. |
- Tang, Yue, et al.
(författare)
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Revisiting GPC and AND Connector in Real-Time Calculus
- 2017
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Ingår i: 2017 IEEE Real-Time Systems Symposium (RTSS). - : IEEE. - 9781538614143 ; , s. 255-265
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Konferensbidrag (refereegranskat)abstract
- Real-Time Calculus (RTC) is a powerful framework for modeling and worst-case performance analysis of networked systems. GPC and AND are two fundamental components in RTC, which model priority-based resource arbitration and synchronization operations, respectively. In this paper, we revisit GPC and AND. For GPC, we develop tighter output arrival curves to more precisely characterize the output event streams. For AND, we first identify a problem in the existing analysis method that may lead to negative values in the output curves, and present corrections to the problem. Then we generalize AND to synchronize more than two input event streams. We implement our new theoretical results and conduct experiments to evaluate their performance. Experiment results show significant improvement of our new methods in analysis precision and efficiency.
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| 29. |
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| 30. |
- Wang, Yang, et al.
(författare)
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Benchmarking OpenMP Programs for Real-Time Scheduling
- 2017
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Ingår i: 2017 IEEE 23Rd International Conference On Embedded And Real-Time Computing Systems And Applications (RTSCA). - : IEEE Computer Society. - 9781538618981
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Konferensbidrag (refereegranskat)abstract
- Real-time systems are shifting from single-core to multi-core processors. Software must be parallelized to fully utilize the computation power of multi-core architecture. OpenMP is a popular parallel programming framework in general and high-performance computing, and recently has drawn a lot of interests in embedded and real-time computing. Much recent work has been done on real-time scheduling of OpenMP-based parallel workload. However, these studies conduct evaluations with randomly generated task systems, which cannot well represent the structure features of OpenMP workload. This paper presents a benchmark suite, ompTGB, to support research on real-time scheduling of OpenMP-based parallel tasks. ompTGB does not only collect realistic OpenMP programs, but also models them into task graphs so that the real-time scheduling researchers can easily understand and use them. We also present a new response time bound for a subset of OpenMP programs and use it to demonstrate the usage of ompTGB.
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| 31. |
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