In this paper, we study and present two techniques to improve the performance of a simulation-based fault injection platform that inserts bit flips in order to model soft errors on digital circuits. The platform is based on the ESA Data Systems Divisionpsilas SEE simulation tool. In contrast with methods based on emulation, the proposed approach reduces the complexity and costs, supplying a test environment with the same reliability as emulation systems. Only one disadvantage appears when comparing both methodologies: the lower performance of the simulation in cases where the fault injection campaigns are very large. Two proposals have been developed in order to address this drawback: the first one is based on software (through checkpoints) and the second one uses parallel computation.
This paper focuses on the integration of the fault injection methodology within the design process of fault-tolerant systems. Due to its wide spectrum of application and hierarchical features, VHDL has been selected as the simulation language to support such an integration. Suitable techniques for injecting faults into VHDL models are identified and depicted. Then, the main features of the MEFISTO environment aimed at supporting these techniques are described. Finally, some preliminary results obtained with MEFISTO are presented and analyzed.<<ETX>>
We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero.