Modeling and Tolerating Heterogeneous Failures on Large Parallel Systems

International audienceAs supercomputers and clusters increase in size and complexity, system failures are inevitable. Different hardware components (such as memory, disk, or network) of such systems can have different failure rates. Prior works assume failures equally affect an application, whereas our goal is to provide failure models for applications that reflect their specific component usage. This is challenging because component failure dynamics are heterogeneous in space and time. To this end, we study 5 years of system logs from a production high-performance computing system and model hard ware failures involving processors, memory, storage and net work components. We model each component and construct integrated failure models given the component us age of common supercomputing applications. We show that these application-centric models provide more accurate reliability estimates compared to general models, which improves the efficacy of fault-tolerant algorithms. In particular, we demonstrate how applications can tune their checkpointing strategies to the tailored model

Use of targeted mobile X-ray screening and computer-aided detection software to identify tuberculosis among high-risk groups in Romania: descriptive results of the E-DETECT TB active case-finding project.

Objective: To implement and assess the mobile X-ray unit (MXU) equipped with digital radiography, computer-aided detection (CAD) software and molecular point of care tests to improve early tuberculosis (TB) diagnosis in vulnerable populations in a TB outreach screening programme in Romania. / Design: Descriptive study. / Settings: Prisons in Bucharest and other cities in the southern part of Romania, homeless shelters and services for problem drug users in Bucharest, and Roma populations in Bucharest and Craiova. / Participants: 5510 individuals attended the MXU service; 5003 persons were radiologically screened, 61% prisoners, 15% prison staff, 11% Roma population, 10% homeless persons and/or problem drug users and 3% other. / Interventions: Radiological digital chest X-ray (CXR) screening of people at risk for TB, followed by CAD and human reading of the CXRs, and further TB diagnostics when the pulmonologist classified the CXR as suggestive for TB. / Primary and secondary outcome measures: Ten bacteriologically confirmed TB cases were identified translating into an overall yield of 200 per 100 000 persons screened (95% CIs of 109 to 368 per 100 000). Prevalence rates among homeless persons and/or problem drug users (826/100 000; 95% CI 326 to 2105/100 000) and the Roma population (345/100 000; 95% CI 95 to 1251/100 000) were particularly high. / Results: The human reader classified 6.4% (n=317) of the CXRs as suspect for TB (of which 32 were highly suggestive for TB); 16.3% of all CXRs had a CAD4TB version 6 score >50. All 10 diagnosed TB patients had a CAD4TB score >50; 9 had a CAD4TB score >60. / Conclusions: Given the high TB prevalence rates found among homeless persons and problem drug users and in the Roma population, targeted active case finding has the potential to deliver a major contribution to TB control in Romania