In an era of complex networked parallel heterogeneous systems, simulating independently only parts, components, or attributes of a system-under-design is a cumbersome, inaccurate, and inefficient approach. Moreover, by considering each part of a system in an isolated manner, and due to the numerous and highly complicated interactions between the different components, the system optimization capabilities are severely limited. The presented fully-distributed simulation framework (called as COSSIM) is the first known open-source, high-performance simulator that can handle holistically system-of-systems including processors, peripherals and networks; such an approach is very appealing to both Cyber Physical Systems (CPS) and Highly Parallel Heterogeneous Systems designers and application developers. Our highly integrated approach is further augmented with accurate power estimation and security sub-tools that can tap on all system components and perform security and robustness analysis of the overall system under design—something that was unfeasible up to now. Additionally, a sophisticated Eclipse-based Graphical User Interface (GUI) has been developed to provide easy simulation setup, execution, and visualization of results. COSSIM has been evaluated when executing the widely used Netperf benchmark suite as well as a number of real-world applications. Final results demonstrate that the presented approach has up to 99% accuracy (when compared with the performance of the real system), while the overall simulation time can be accelerated almost linearly with the number of CPUs utilized by the simulator.

The growing use of Cyber-Physical Systems (CPS) in a plethora of domains (e.g. healthcare, industry, smart homes, transportation, etc.) triggers an urgent demand for simulation frameworks that can simulate in an integrated manner all the components (i.e. CPUs, Memories, Networks, Physical Environment) of a system-under-design(SuD). By utilizing such a simulator, software design can proceed in parallel with physical development which results in the reduction of the so important time-to-market. The main problem, however, is that currently there is a shortage of such simulation frameworks; most simulators used for modelling the digital aspects of CPS applications (i.e. full-system CPU/Mem/Peripheral simulators) lack any support of the CPS physical aspects and vice versa. The presented fully-distributed simulation framework (APOLLON) is the first known open-source, high-performance simulator that can handle holistically complex CPSs including processors, peripherals, networks and physical aspects of them. APOLLON is an extension of the COSSIM simulation framework and it integrates, in a novel and efficient way, a combined processing and network simulator with the widely-used Ptolemy physical simulator, in a transparent way. Our highly integrated approach is further augmented with Machine Learning capabilities by implementing Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) recurrent neural networks in both the Cyber and Physical domains, enabling users to develop their complex recurrent neural networks significantly fast and accurately. APOLLON has been evaluated when executing a number of benchmarks and real-world use cases; the end results demonstrate that the presented approach has up to 99% accuracy in the reported SuD aspects.

This paper introduces a novel electroencephalogram (EEG) data classification scheme together with its implementation in hardware using an innovative approach. The proposed scheme integrates into a single, end-to-end trainable model a spatial filtering technique and a neural network based classifier. The spatial filters, as well as, the coefficients of the neural network classifier are simultaneously estimated during training. By using different time-locked spatial filters, we introduce for the first time the notion of "attention" in EEG processing, which allows for the efficient capturing of the temporal dependencies and/ or variability of the EEG sequential data. One of the most important benefits of our approach is that the proposed classifier is able to construct highly discriminative features directly from raw EEG data and, at the same time, to exploit the function approximation properties of neural networks, in order to produce highly accurate classification results. The evaluation of the proposed methodology, using public available EEG datasets, indicates that it outperforms the standard EEG classification approach based on filtering and classification as two separated steps. Moreover, we present a prototype implementation of the proposed scheme in state-of-the-art reconfigurable hardware; our novel implementation outperforms by more than an order of magnitude, in terms of power efficiency, the conventional CPU-based approaches.

The growing use of hardware accelerators in both embedded (e.g. automotive) and high-end systems (e.g. Cloud infrastructure) triggers an urgent demand for simulation frameworks that can simulate in an integrated manner all the components (i.e. CPUs, Memories, Networks, Hardware Accelerators) of a system-under-design(SuD). By utilizing such a simulator, software design can proceed in parallel with hardware development which results in the reduction of the so important time-to-market. The main problem, however, is that currently there is a shortage of such simulation frameworks; most simulators used for modelling the user-applications lack any type of support for tailor-made hardware accelerators. The presented ACSIM framework is the first known open-source, high-performance simulator that can handle holistically system-of-systems including processors, peripherals, accelerators and networks; such an approach is, for example, very appealing for the design of Cloud Servers that incorporate FPGAs as PCI-connected accelerators. ACSIM is an extension of the COSSIM simulation framework and it integrates, in a novel and efficient way, a combined system and network simulator with a SystemC simulator, in a transparent to the end-user way. ACSIM can efficiently simulate up to several hundreds of processing nodes with hardware accelerators interconnected together, in a fully distributed manner.

In recent years, systems that monitor and control home environments, based on non-vocal and non-manual interfaces, have been introduced to improve the quality of life of people with mobility difficulties. In this work, we present the reconfigurable implementation and optimization of such a novel system that utilizes a recurrent neural network (RNN). As demonstrated in the real-world results, FPGAs have proved to be very efficient when implementing RNNs. In particular, our reconfigurable implementation is more than 150× faster than a high-end Intel Xeon CPU executing the reference inference tasks. Moreover, the proposed system achieves more than 300× the improvements, in terms of energy efficiency, when compared with the server CPU, while, in terms of the reported achieved GFLOPS/W, it outperforms even a server-tailored GPU. An additional important contribution of the work discussed in this study is that the implementation and optimization process demonstrated can also act as a reference to anyone implementing the inference tasks of RNNs in reconfigurable hardware; this is further facilitated by the fact that our C++ code, which is tailored for a high-level-synthesis (HLS) tool, is distributed in open-source, and can easily be incorporated to existing HLS libraries.