Comparative performance evaluation of latency and link dynamic power consumption modelling algorithms in wormhole switching networks on chip

The simulation of interconnect architectures can be a time-consuming part of the design flow of on-chip multiprocessors. Accurate simulation of state-of-the art network-on-chip interconnects can take several hours for realistic application examples, and this process must be repeated for each design iteration because the interactions between design choices can greatly affect the overall throughput and latency performance of the system. This paper presents a series of network-on-chip transaction-level model (TLM) algorithms that provide a highly abstracted view of the process of data transmission in priority preemptive and non-preemptive networks-on-chip, which permit a major reduction in simulation event count. These simulation models are tested using two realistic application case studies and with synthetic traffic. Results presented demonstrate that these lightweight TLM simulation models can produce latency figures accurate to within mere flits for the majority of flows, and more than 93% accurate link dynamic power consumption modelling, while simulating 2.5 to 3 orders of magnitude faster when compared to a cycle-accurate model of the same interconnect

COUNTERTRANSFERENCE REACTIONS IN A CROSS-RACIAL DYAD: THE ROLE OF THERAPIST UNIVERSAL-DIVERSE ORIENTATION AND PRESENTATION OF CLIENT STRENGTHS

The purpose of this study was to examine the influence of universal-diverse orientation (UDO) and information on client strengths on European American therapists' countertransference to an angry African American client. Forty-five European American therapist trainees completed a measure of UDO and were randomly assigned to one of two conditions in which they were either given or not given information on client strengths. Therapists then watched and responded to a videotape of an angry African American client. Countertransference was measured in terms of therapist state anxiety, cognitive recall, and behavioral avoidance. Results showed that therapist UDO was significantly and negatively related to their countertransference reactions in a cross-racial situation. Additionally, results were not significant for the main effect of information on client strengths and for the interaction of UDO and information on client strengths on countertransference reactions. Implications for counseling and future research were explored

Therapist work with client strengths: Development and validation of a measure

Drawing from the positive psychology literature, the Inventory of Therapist Work with Strengths and Assets (IT-WAS) was constructed to measure the degree to which clinicians incorporate strength-based approaches in their therapy work. Two different samples were gathered in the current study; a professional sample (n = 128) and a university sample (n = 97). The professional sample was randomly selected from the 2005 membership directory of Divisions 17 (Counseling Psychology), 29 (Psychotherapy), and 42 (Independent Practice) of the American Psychological Association (APA), and resulted in a 51% return rate. The university sample consisted of graduate students in counseling related fields as well as faculty and counseling center staff at a large Mid-Atlantic university; the return rate for this sample was 62%. T-test results found no significant differences between samples on IT-WAS scores, and thus samples were combined for analyses. Three factors (Theory of Intervention, Strength Assessment, & Supporting Progress) were extracted by factor analysis, accounting for 52% of the total variance. The IT-WAS demonstrated very good internal consistency (α = .96) and test-retest reliability (r = .83). Scale validity was supported by positive associations between the IT-WAS and measures of favorable attitudes toward human nature, benevolent world assumptions, as well as therapist work with the strengths of a most recent client. Most therapists generally conducted strength-based clinical work to a high degree, supporting propositions made by Seligman (2002; Seligman & Peterson, 2003). Cognitive-behavioral, humanistic, multicultural, and feminist theoretical orientations were positively related to the IT-WAS, while psychodynamic and psychoanalytic theoretical orientations were negatively correlated to the IT-WAS. No differences between clinical and counseling psychologists were found on IT-WAS scores. Implications of therapist work with client strengths are discussed and areas for future research are provided

Side-Channel Protected MPSoC through Secure Real-Time Networks-on-Chip

The integration of Multi-Processors System-on-Chip (MPSoCs) into the Internet -of -Things (IoT) context brings new opportunities, but also represent risks. Tight real-time constraints and security requirements should be considered simultaneously when designing MPSoCs. Network-on-Chip (NoCs) are specially critical when meeting these two conflicting characteristics. For instance the NoC design has a huge influence in the security of the system. A vital threat to system security are so-called side-channel attacks based on the NoC communication observations. To this end, we propose a NoC security mechanism suitable for hard real-time systems, in which schedulability is a vital design requirement. We present three contributions. First, we show the impact of the NoC routing in the security of the system. Second, we propose a packet route randomisation mechanism to increase NoC resilience against side-channel attacks. Third, using an evolutionary optimisation approach, we effectively apply route randomisation while controlling its impact on hard real-time performance guarantees. Extensive experimental evidence based on analytical and simulation models supports our findings

AirTight: A Resilient Wireless Communication Protocol for Mixed-Criticality Systems

This paper describes the motivation, design, analysis and implementation of a new protocol for critical wireless communication called AirTight. Wireless communication has become a crucial part of the infrastructure of many cyber-physical applications. Many of these applications are real-time and also mixed-criticality, in that they have components/subsystems with different consequences of failure. Wireless communication is inevitably subject to levels of external interference. In this paper we represent this interference using a criticality-aware fault model; for each level of interference in the fault model we guarantee the timing behaviour of the protocol (i.e.~we guarantee that packet deadlines are satisfied for certainly levels of criticality). Although a new protocol, AirTight is built upon existing standards such as IEEE 802.15.4. A prototype implementation and protocol-accurate simulator, which are also built upon existing technologies, demonstrate the effectiveness and functionality of the protocol

Fast simulation of networks-on-chip with priority-preemptive arbitration

An increasingly time-consuming part of the design flow of on-chip multiprocessors is the simulation of the interconnect architecture. The accurate simulation of state-of-the art network-on-chip interconnects can take hours, and this process is repeated for each design iteration because it provides valuable insights on communication latencies that can greatly affect the overall performance of the system. In this article, we identify a time-predictable network-on-chip architecture and show that its timing behaviour can be predicted using models which are far less complex than the architecture itself. We then explore such a feature to produce simplified and lightweight simulation models that can produce latency figures with more than 90% accuracy and simulate more than 1,000 times faster when compared to a cycle-accurate model of the same interconnect

Model-Driven Simulation-Based Analysis for Multi-Robot Systems

Multi-robot systems are increasingly deployed to provide services and accomplish missions whose complexity or cost is too high for a single robot to achieve on its own. Although multi-robot systems offer increased reliability via redundancy and enable the execution of more challenging missions, engineering these systems is very complex. This complexity affects not only the architecture modelling of the robotic team but also the modelling and analysis of the collaborative intelligence enabling the team to complete its mission. Existing approaches for the development of multi-robot applications do not provide a systematic mechanism for capturing these aspects and assessing the robustness of multi-robot systems. We address this gap by introducing ATLAS, a novel model-driven approach supporting the systematic robustness analysis of multi-robot systems in simulation. The ATLAS domain-specific language enables modelling the architecture of the robotic team and its mission, and facilitates the specification of the team’s intelligence. We evaluate ATLAS and demonstrate its effectiveness on two oceanic exploration missions performed by a team of unmanned underwater vehicles developed using the MOOS-IvP robotic simulator

Validating High Level Simulation Results against Experimental Data and Low Level Simulation : A Case Study

Simulation can be considered a necessary evil in the validation of systems, especially when the system under consideration is being prototyped and therefore does not presently exist. This is compounded by the use of high level simulators; on the one hand, high level simulation is efficient, in that it abstracts away many details of the system which are deemed to be not important. This allows for a simpler and faster running simulator, which allows the user to obtain results faster and/or perform more experiments. On the other hand, some of the details abstracted away might turn out to be important, introducing inaccuracies. This paper outlines a framework for the statistical understanding and attribution of the errors produced by a high level simulator when compared against real experiments by means of a low level simulator. This allows the user of a simulator to determine whether or not the inaccuracies are significant, and whether or not the high level simulator requires refinements in its accuracy for the results to be valid. These techniques are illustrated via a case study

The AirTight Protocol for Mixed Criticality Wireless CPS

This paper describes the motivation, design, analysis and configuration of the criticality-aware multi-hop wireless communication protocol AirTight. Wireless communication has become a crucial part of the infrastructure of many cyber-physical applications. Many of these applications are real-time and also mixed-criticality, in that they have components/subsystems with different consequences of failure. Wireless communication is inevitably subject to levels of external interference. In this paper we represent this interference using a criticality-aware fault model; for each level of temporal interference in the fault model we guarantee the timing behaviour of the protocol (i.e.~we guarantee that packet deadlines are satisfied for certain levels of criticality). Although a new protocol, AirTight is built upon existing standards such as IEEE 802.15.4. A prototype implementation and protocol-accurate simulator have been produced. This paper develops a series of schedulability analysis techniques for single-channel and multichannel wireless Cyber-Physical Systems (CPS). Heuristics are specified and evaluated as the starting point of design space exploration. Genetic algorithms are then defined and evaluated to assess their performance in developing schedule tables incorporating multichannel allocations in these systems

Supporting Critical Modes in AirTight

The AirTight protocol supports mixed criticality wireless traffic and temporal guarantees based on defined fault models. In some systems, following a catastrophic failure, it is necessary to communicate crucial data away from the site of the failure in order to better understand (post-hoc) the reasons why it occurred. To support this action it is necessary for a mode change request to be propagated to all the non-failed nodes in the system, and for these nodes to switch their behaviour so that the crucial data is given high priority in its use of the wireless network. This paper explains how Airtight can support such a critical mode change. A uni-cast protocol is utilised to flood the system with mode change messages, each node then locally prioritizes its use of the available bandwidth to support the defined UC (Ultra-Criticality) packet flows. An aircraft engine control scenario is used to motivate the requirements for the mode change protocol. Protocol-accurate simulations are then used to illustrate and evaluate the approach