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- Bonna, Ricardo, et al.
(author)
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Modeling and Simulation of Dynamic Applications Using Scenario-Aware Dataflow
- 2019
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In: ACM Transactions on Design Automation of Electronic Systems. - : ASSOC COMPUTING MACHINERY. - 1084-4309 .- 1557-7309. ; 24:5
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Journal article (peer-reviewed)abstract
- The tradeoff between analyzability and expressiveness is a key factor when choosing a suitable dataflow model of computation (MoC) for designing, modeling, and simulating applications considering a formal base. A large number of techniques and analysis tools exist for static dataflow models, such as synchronous dataflow. However, they cannot express the dynamic behavior required for more dynamic applications in signal streaming or to model runtime reconfigurable systems. On the other hand, dynamic dataflow models like Kahn process networks sacrifice analyzability for expressiveness. Scenario-aware dataflow (SADF) is an excellent tradeoff providing sufficient expressiveness for dynamic systems, while still giving access to powerful analysis methods. In spite of an increasing interest in SADF methods, there is a lack of formally-defined functional models for describing and simulating SADF systems. This article overcomes the current situation by introducing a functional model for the SADF MoC, as well as a set of abstract operations for simulating it. We present the first modeling and simulation tool for SADF so far, implemented as an open source library in the functional framework ForSyDe. We demonstrate the capabilities of the functional model through a comprehensive tutorial-style example of a RISC processor described as an SADF application, and a traditional streaming application where we model an MPEG-4 simple profile decoder. We also present a couple of alternative approaches for functionally modeling SADF on different languages and paradigms. One of such approaches is used in a performance comparison with our functional model using the MPEG-4 simple profile decoder as a test case. As a result, our proposed model presented a good tradeoff between execution time and implementation succinctness. Finally, we discuss the potential of our formal model as a frontend for formal system design flows regarding dynamic applications.
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- de Medeiros, Jose. E. G., et al.
(author)
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An Algebra for Modeling Continuous Time Systems
- 2018
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In: PROCEEDINGS OF THE 2018 DESIGN, AUTOMATION & TEST IN EUROPE CONFERENCE & EXHIBITION (DATE). - : IEEE. - 9783981926309 ; , s. 861-864
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Conference paper (peer-reviewed)abstract
- Advancements on analog integrated design have led to new possibilities for complex systems combining both continuous and discrete time modules on a signal processing chain. However, this also increases the complexity any design flow needs to address in order to describe a synergy between the two domains, as the interactions between them should be better understood. We believe that a common language for describing continuous and discrete time computations is beneficial for such a goal and a step towards it is to gain insight and describe more fundamental building blocks. In this work we present an algebra based on the General Purpose Analog Computer, a theoretical model of computation recently updated as a continuous time equivalent of the Turing Machine.
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| 7. |
- Loubach, Denis S., et al.
(author)
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Classification and Mapping of Model Elements for Designing Runtime Reconfigurable Systems
- 2021
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In: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 9, s. 156337-156360
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Journal article (peer-reviewed)abstract
- Embedded systems are ubiquitous and control many critical functions in society. A fairly new type of embedded system has emerged with the advent of partial reconfiguration, i.e. runtime reconfigurable systems. They are attracting interest in many different applications. Such a system is capable of reconfiguring itself at the hardware level and without the need to halt the application's execution. While modeling and implementing these systems is far from a trivial task, there is currently a lack of systematic approaches to tackle this issue. In other words, there is no unanimously agreed upon modeling paradigm that can capture adaptive behaviors at the highest level of abstraction, especially when regarding the design entry, namely, the initial high-level application and platform models. Given this, our paper proposes two domain ontologies for application and virtual platform models used to derive a classification system and to provide a set of rules on how the different model elements are allowed to be composed together. The application behavior is captured through a formal model of computation which dictates the semantics of execution, concurrency, and synchronization. The main contribution of this paper is to combine suitable formal models of computation, a functional modeling language, and two domain ontologies to create a systematic design flow from an abstract executable application model into a virtual implementation model based on a runtime reconfigurable architecture (virtual platform model) using well-defined mapping rules. We demonstrate the applicability, generality, and potential of the proposed model element classification system and mapping rules by applying them to representative and complete examples: an encoder/decoder system and an avionics attitude estimation system. Both cases yield a virtual implementation model from an abstract application model.
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| 8. |
- Rosvall, Kathrin, et al.
(author)
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Exploring Power and Throughput for Dataflow Applications on Predictable NoC Multiprocessors
- 2018
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Conference paper (peer-reviewed)abstract
- System level optimization for multiple mixed-criticality applications on shared networked multiprocessor platforms is extremely challenging. Substantial complexity arises from the interdependence between the multiple subproblems of mapping, scheduling and platform configuration under the consideration of several, potentially orthogonal, performance metrics and constraints. Instead of using heuristic algorithms and problem decomposition, novel unified design space exploration (DSE) approaches based on Constraint Programming (CP) have in the recent years shown promising results. The work in this paper takes advantage of the modularity of CP models, in order to support heterogeneous multiprocessor Network-on-Chip (NoC) with Temporally Disjoint Networks (TDNs) aware message injection. The DSE supports a range of design criteria, in particular the optimization and satisfaction of power and throughput. In addition, the DSE now provides a valid configuration for the TDNs that guarantees the performance required to fulfil the design goals. The experiments show the capability of the approach to find low-power and high-throughput designs, and validate a resulting design on a physical TDN-based NoC implementation.
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| 9. |
- Rosvall, Kathrin, et al.
(author)
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Throughput propagation in constraint-based design space exploration for mixed-criticality systems
- 2017
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In: ACM International Conference Proceeding Series. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450348409
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Conference paper (peer-reviewed)abstract
- When designing complex mixed-critical systems on multiprocessor platforms, a huge number of design alternatives has to be evaluated. Therefore, there is a need for tools which systematically find and analyze the ample alternatives and identify solutions that satisfy the design constraints. The recently proposed design space exploration (DSE) tool DeSyDe uses constraint programming (CP) to find implementations with performance guarantees for multiple applications with potentially mixed-critical design constraints on a shared platform. A key component of the DeSyDe tool is its throughput analysis component, called a throughput propagator in the context of CP. The throughput propagator guides the exploration by evaluating each design decision and is therefore executed excessively throughout the exploration. This paper presents two throughput propagators based on different analysis methods for DeSyDe. Their performance is evaluated in a range of experiments with six different application graphs, heterogeneous platform models and mixed-critical design constraints. The results suggest that the MCR throughput propagator is more efficient.
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| 10. |
- Ungureanu, George, et al.
(author)
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A layered formal framework for modeling of cyber-physical systems
- 2017
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In: Proceedings of the 2017 Design, Automation and Test in Europe, DATE 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783981537093 ; , s. 1715-1720
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Conference paper (peer-reviewed)abstract
- Designing cyber-physical systems is highly challenging due to its manifold interdependent aspects such as composition, timing, synchronization and behavior. Several formal models exist for description and analysis of these aspects, but they focus mainly on a single or only a few system properties. We propose a formal composable framework which tackles these concerns in isolation, while capturing interaction between them as a single layered model. This yields a holistic, fine-grained, hierarchical and structured view of a cyber-physical system. We demonstrate the various benefits for modeling, analysis and synthesis through a typical example.
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| 11. |
- Ungureanu, George, et al.
(author)
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Bridging Discrete and Continuous Time Models with Atoms
- 2018
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In: PROCEEDINGS OF THE 2018 DESIGN, AUTOMATION & TEST IN EUROPE CONFERENCE & EXHIBITION (DATE). - : IEEE. - 9783981926309 ; , s. 277-280
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Conference paper (peer-reviewed)abstract
- Recent trends in replacing traditionally digital components with analog counterparts in order to overcome physical limitations have led to an increasing need for rigorous modeling and simulation of hybrid systems. Combining the two domains under the same set of semantics is not straightforward and often leads to chaotic and non-deterministic behavior due to the lack of a common understanding of aspects concerning time. We propose an algebra of primitive interactions between continuous and discrete aspects of systems which enables their description within two orthogonal layers of computation. We show its benefits from the perspective of modeling and simulation, through the example of an RC oscillator modeled in a formal framework implementing this algebra.
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| 12. |
- Ungureanu, George, et al.
(author)
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Exploiting Dataflow Models for Parallel Simulation of Discrete Timed Systems
- 2020
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In: Proceedings of the 2020 Forum for Specification & Design Languages (FDL). - Kiel, Germany : Institute of Electrical and Electronics Engineers (IEEE).
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Conference paper (peer-reviewed)abstract
- The shift towards parallel computing witnessed since the turn of this century has forced us to rethink traditional software design paradigms to better utilize resources. Yet, the simulation of time-aware systems remains a challenging topic due to the inherent semantics of time and causality whose consistency needs to be controlled, traditionally in form of a global event queue, limiting the potential for parallel exploitation. We propose a rehash of this problem by tackling it from a different modeling perspective, one which is able to express concurrency more naturally, i.e. dataflow (DF) models of computation (MoCs). By abstracting time aspects as an algebra hosted on a pure DF MoC, we are able to apply recent results from MoC theory not only for the purpose of describing deterministic behaviors for distributed timed systems, but also to overcome the existing limitations of timed execution in order to increase a simulation model's performance. We use a well-known example of a deadlock-prone distributed discrete event system as a driver to introduce the modeling concepts and show their potential for parallelism.
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| 13. |
- Ungureanu, George, et al.
(author)
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Formal design, co-simulation and validation of a radar signal processing system
- 2019
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In: Proceedings of the 2019 Forum on Specification and Design Languages, FDL 2019. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728141138
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Conference paper (peer-reviewed)abstract
- With the ever increasing complexity in safety-critical and performance-demanding application domains such as automotive and avionics, the costs of designing, producing and especially testing systems does not scale well for the next generation of applications. One example is the active electronically scanned array (AESA) antenna signal processing chain, which is currently out-of-reach from consumer products but rather part of a few exclusive hi-tech appliances. To cope with the associated complexity of such systems, we propose a design flow starting from a high-level formal modeling language which captures and exposes important design properties to enable their systematic exploitation for the purpose of simulation, analysis and synthesis towards cost-efficient implementations. We demonstrate the capabilities of this approach by providing a compact yet expressive description of the AESA signal processing chain, generate automatic test-cases to verify the conformity of model with design specifications, synthesize a part of it to VHDL and co-simulate the generated artifact to validate its correctness.
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| 14. |
- Ungureanu, George, et al.
(author)
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ForSyDe-Atom : Taming Complexity in Cyber Physical System Design with Layers
- 2021
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In: ACM Transactions on Embedded Computing Systems. - : Association for Computing Machinery (ACM). - 1539-9087 .- 1558-3465. ; 20:2
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Journal article (peer-reviewed)abstract
- We present ForSyDe-Atom, a formal framework intended as an entry point for disciplined design of complex cyber-physical systems. This framework provides a set of rules for combining several domain-specific languages as structured, enclosing layers to orthogonalize the many aspects of system behavior, yet study their interaction in tandem. We define four layers: one for capturing timed interactions in heterogeneous systems, one for structured parallelism, one for modeling uncertainty, and one for describing component properties. This framework enables a systematic exploitation of design properties in a design flow by facilitating the stepwise projection of certain layers of interest, the isolated analysis and refinement on projections, and the seamless reconstruction of a system model by virtue of orthogonalization. We demonstrate the capabilities of this approach by providing a compact yet expressive model of an active electronically scanned array antenna and signal processing chain, simulate it, validate its conformity with the design specifications, refine it, synthesize a sub-system to VHDL and sequential code, and co-simulate the generated artifacts.
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| 15. |
- Ungureanu, George
(author)
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ForSyDe-Atom: Design of Heterogeneous Embedded Systems : Taming Complexity with Layers, Atoms and Patterns
- 2021
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Doctoral thesis (other academic/artistic)abstract
- The design of embedded systems is inherently complex for two main reasons. Firstly, it entails the combined knowledge and results from a vast set of mature, well-established, yet separate disciplines, such as electrical engineering, computer science, mechanical engineering, etc. Secondly, it needs to account for the collective behavior of computing elements, infrastructure and physical environment. This behavior cannot be derived from the sum of its constituent components, rather it emerges from the manifold feedback interactions between them. One of the main tools that have enabled engineers to guide the development of systems with unprecedented complexity is abstraction, that is, capturing essential properties of phenomena into mathematical, well-behaved analyzable models. Yet combining models from different disciplines is largely limited due to the fact that these models, although well-acknowledged, are most often incompatible. In a system design process, this leads to the discovery and understanding of unwanted or hazardous behaviors during later stages such as prototyping or deployment phases, when design reiterations are extremely costly.This thesis introduces ForSyDe-Atom, a formal framework intended as an entry point for the disciplined design of embedded systems. This framework provides a set of rules for combining several domain specific languages as structured, enclosing layers in order to orthogonalize the many aspects of system behavior, yet study their interaction in tandem. It enables systematic exploitation of design properties in a system design flow by facilitating the step-wise projection of certain layers of interest, the isolated analysis and refinement on projections and the seamless reconstruction of a system model from (possibly refined) projections. As examples of languages hosted by this framework, five layers are presented: one for capturing timed interactions in heterogeneous systems, one for extending behaviors with controlled effects, one for structured parallelism, one for modeling uncertainty and one for describing component properties. The modeling capabilities are demonstrated through numerous didactic examples and four large case studies from the application domains of digital signal processing and avionics. A set of strategies for parallelizing timed simulation models, together with a preliminary component-based synthesis flow towards embedded platforms further highlight the potential of this framework as an entry point to system design.
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| 16. |
- Ungureanu, George, et al.
(author)
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Parallel software design enabling high-speed reliability testing of inkjet printheads
- 2013
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In: International Conference on Digital Printing Technologies. - 9780892083060 ; , s. 60-65
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Conference paper (peer-reviewed)abstract
- With new functional applications emerging in the digital printing industry, the need for quantitative knowledge of the reliability of drop-on-demand inkjet printheads increases. Continuous ink circulation using TF Technology™and the resulting channel self-recovery is one of the technologies which decrease the down-time of a single nozzle, but in turn increase the difficulty of an accurate reliability test. Current measuring techniques, namely the a-posteriori verification of printouts on paper proved to be inappropriate. This paper proposes a novel software approach, exploiting signal processing techniques, strong control loops and powerful system design methodologies in order to allow for the correct detection of single missing droplets at run-time. This new system is meant to relieve the effects of the indefinite environment and sources of human error. Preliminary results and the proof-ofconcept demonstrates both the system's and the design method's versatility and potential.
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