Fault tolerance in super-scalar and VLIW processors

In this paper, we present a method for utilizing the spare capacity in super-scalar and very long instruction word (VLIW) processors to tolerate functional unit failures. Unlike previous work that was primarily interested in detection of transient faults, we are concerned with more permanent and/or intermittent faults which necessitate processor reconfiguration. Our method utilizes the VLIW compiler or the superscalar scheduler to insert redundant operations whenever idle functional units exist. The results of these redundant operations are used to detect and diagnose functional unit failures. For super-scalar processors, the scheduler can then utilize this information to ensure that operations are performed only on non-faulty units. In VLIW processors, this is equivalent to recompiling the code to run on the remaining non-faulty functional units. Since in certain applications, recompilation may not be possible, we consider two alternative reconfiguration strategies for VLIW processors. These strategies sacrifice storage space and execution time, respectively, in order to reconfigure without recompiling. We present Markov models that describe the behavior of processors using these different approaches and we evaluate their reliabilities. The results show that, while super-scalar and VLIW with recompilation provide the highest reliability, all proposed strategies significantly increase reliability over that of an unprotected processor

Transparent-Influx Boundary Conditions for FEM Based Modelling of 2D Helmholtz Problems in Optics

A numerical method for the analysis of the 2D Helmholtz equation is presented, which incorporates Transparent-Influx Boundary Conditions into a variational formulation of the Helmholtz problem. For rectangular geometries, the non-locality of those boundaries can be efficiently handled by using Fourier decomposition. The Finite Element Method is used to discretise the interior and the nonlocal Dirichlet-to-Neumann operators arising from the formulation of Transparent-Influx Boundary Conditions

Urban Heritage Dynamics in ‘Heritage-Led Regeneration’: Towards a Sustainable Lifestyles Approach

This paper aims to introduce a novel approach to sustainable heritage-led urban regeneration. More specifically, the paper proposes a new heritage-led urban regeneration paradigm that has communities and sustainable lifestyles at its core. The paper concludes with this approach after analysing current paradigms of heritage-led urban regeneration through system dynamics. We have chosen to analyse though system dynamics a longitudinal study of the Townscape Heritage Initiative (THI), a heritage-led regeneration scheme funded by the Heritage Lottery Fund. Our system dynamic analysis unveils the absence of environmental sustainability concerns in current heritage-led regeneration examples as well as the critical role of the existence of concerted, strategic and participatory vision of a heritage-led urban regeneration programme. The critical, systemic and dynamic analysis of the THI longitudinal study provides the basis for developing a new approach towards sustainable heritage-led regeneration which has communities and sustainable lifestyles at its core. Although we acknowledge that extensive applied and theoretical research is needed to validate or enhance the proposed approach, we do cite sporadic examples that provide some first indications of the effectiveness of the approach