861,629 research outputs found
Performance Evaluation of Software using Formal Methods
Formal Methods (FMs) can be used in varied areas of applications and to solve critical and fundamental problems of Performance Evaluation (PE). Modelling and analysis techniques can be used for both system and software performance evaluation. The functional features and performance properties of modern software used for performance evaluation has become so intertwined. Traditional models and methods for performance evaluation has been studied widely which culminated into the modern models and methods for system and software engineering evaluation such as formal methods. Techniques have transcended from functionality to performance modeling and analysis. Formal models help in identifying faulty reasoning far earlier than in traditional design; and formal specification has proved useful even on already existing software and systems. Formal approach eliminates ambiguity. The basic and final goal of the performance evaluation technique is to come to a conclusion, whether the software and system are working in a good condition or satisfactorily
Construction and Verification of Performance and Reliability Models
Over the last two decades formal methods have been extended towards performance and reliability evaluation. This paper tries to provide a rather intuitive explanation of the basic concepts and features in this area.
Instead of striving for mathematical rigour, the intention is to give an illustrative introduction to the basics of stochastic models, to stochastic modelling using process algebra, and to model checking as a technique to analyse stochastic models
Reliability and risk assessment of structures
Development of reliability and risk assessment of structural components and structures is a major activity at Lewis Research Center. It consists of five program elements: (1) probabilistic loads; (2) probabilistic finite element analysis; (3) probabilistic material behavior; (4) assessment of reliability and risk; and (5) probabilistic structural performance evaluation. Recent progress includes: (1) the evaluation of the various uncertainties in terms of cumulative distribution functions for various structural response variables based on known or assumed uncertainties in primitive structural variables; (2) evaluation of the failure probability; (3) reliability and risk-cost assessment; and (4) an outline of an emerging approach for eventual certification of man-rated structures by computational methods. Collectively, the results demonstrate that the structural durability/reliability of man-rated structural components and structures can be effectively evaluated by using formal probabilistic methods
Designing a CPU model: from a pseudo-formal document to fast code
For validating low level embedded software, engineers use simulators that
take the real binary as input. Like the real hardware, these full-system
simulators are organized as a set of components. The main component is the CPU
simulator (ISS), because it is the usual bottleneck for the simulation speed,
and its development is a long and repetitive task. Previous work showed that an
ISS can be generated from an Architecture Description Language (ADL). In the
work reported in this paper, we generate a CPU simulator directly from the
pseudo-formal descriptions of the reference manual. For each instruction, we
extract the information describing its behavior, its binary encoding, and its
assembly syntax. Next, after automatically applying many optimizations on the
extracted information, we generate a SystemC/TLM ISS. We also generate tests
for the decoder and a formal specification in Coq. Experiments show that the
generated ISS is as fast and stable as our previous hand-written ISS.Comment: 3rd Workshop on: Rapid Simulation and Performance Evaluation: Methods
and Tools (2011
Probabilistic simulation of uncertainties in thermal structures
Development of probabilistic structural analysis methods for hot structures is a major activity at Lewis Research Center. It consists of five program elements: (1) probabilistic loads; (2) probabilistic finite element analysis; (3) probabilistic material behavior; (4) assessment of reliability and risk; and (5) probabilistic structural performance evaluation. Recent progress includes: (1) quantification of the effects of uncertainties for several variables on high pressure fuel turbopump (HPFT) blade temperature, pressure, and torque of the Space Shuttle Main Engine (SSME); (2) the evaluation of the cumulative distribution function for various structural response variables based on assumed uncertainties in primitive structural variables; (3) evaluation of the failure probability; (4) reliability and risk-cost assessment, and (5) an outline of an emerging approach for eventual hot structures certification. Collectively, the results demonstrate that the structural durability/reliability of hot structural components can be effectively evaluated in a formal probabilistic framework. In addition, the approach can be readily extended to computationally simulate certification of hot structures for aerospace environments
Advanced flight control system study
A fly by wire flight control system architecture designed for high reliability includes spare sensor and computer elements to permit safe dispatch with failed elements, thereby reducing unscheduled maintenance. A methodology capable of demonstrating that the architecture does achieve the predicted performance characteristics consists of a hierarchy of activities ranging from analytical calculations of system reliability and formal methods of software verification to iron bird testing followed by flight evaluation. Interfacing this architecture to the Lockheed S-3A aircraft for flight test is discussed. This testbed vehicle can be expanded to support flight experiments in advanced aerodynamics, electromechanical actuators, secondary power systems, flight management, new displays, and air traffic control concepts
Performance modelling of applications in a smart environment
PhD ThesisIn today’s world, advanced computing technology has been widely used to improve
our living conditions and facilitate people’s daily activities. Smart environment
technology, including kinds of smart devices and intelligent systems, is now being
researched to provide an advanced intelligent life, easy, comfortable environment.
This thesis is aimed to investigate several related technologies corresponding to the
design of a smart environment. Meanwhile, this thesis also explores different
modelling approaches including formal methods and discrete event simulation.
The core contents of the thesis include performance evaluation of scheduling
policies and capacity planning strategies. The main contribution is in developing a
modelling approach for smart hospital environments. This thesis also provides
valuable experience in the formal modelling and the simulation of large scale
systems.
The chief findings are that the dynamic scheduling policy is proved to be the most
efficient approach in the scheduling process; and a capacity scheme is also verified
as the optimal scheme to obtain the high work efficiency under the condition of
limited human resource.
The main methods used for the performance modelling are Performance Evaluation
Process Algebra (PEPA) and discrete event simulation. A great deal of modelling
tasks was completed with these methods. For the analysis, we adopt both numerical
analysis based on PEPA models and statistical measurements in the simulation
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