Performance Analysis of a Consensus Algorithm Combining Stochastic Activity Networks and Measurements

A. Coccoli, P. Urban, A. Bondavalli, and A. Schiper. Performance analysis of a consensus algorithm combining Stochastic Activity Networks and measurements. In Proc. Int'l Conf. on Dependable Systems and Networks (DSN), pages 551-560, Washington, DC, USA, June 2002. Protocols which solve agreement problems are essential building blocks for fault tolerant distributed applications. While many protocols have been published, little has been done to analyze their performance. This paper represents a starting point for such studies, by focusing on the consensus problem, a problem related to most other agreement problems. The paper analyzes the latency of a consensus algorithm designed for the asynchronous model with failure detectors, by combining experiments on a cluster of PCs and simulation using Stochastic Activity Networks. We evaluated the latency in runs (1) with no failures nor failure suspicions, (2) with failures but no wrong suspicions and (3) with no failures but with (wrong) failure suspicions. We validated the adequacy and the usability of the Stochastic Activity Network model by comparing experimental results with those obtained from the model. This has led us to identify limitations of the model and the measurements, and suggests new directions for evaluating the performance of agreement protocols. Keywords: quantitative analysis, distributed consensus, failure detectors, Stochastic Activity Networks, measurement

Performance comparison between the Paxos and Chandra-Toueg consensus algorithms

Protocols which solve agreement problems are essential building blocks for fault tolerant distributed applications. While many protocols have been published, little has been done to analyze their performance. This paper represents a starting point for such studies, by focusing on the consensus problem, a problem related to most other agreement problems. The paper compares the latency of two consensus algorithms designed for the asynchronous model with failure detectors: the Paxos algorithm and the Chandra-Toueg algorithm. We varied the number of processes which take part in the execution. Moreover, we evaluated the latency in different classes of runs: (1) runs with no failures nor failure suspicions, (2) runs with failures but no wrong suspicions. We determined the latency by measurements on a cluster of PCs interconnected with a 100 Mbps Ethernet network. We found that the Paxos algorithm is more efficient than the Chandra-Toueg algorithm when the process that coordinates the first round of the protocol crashes. The two algorithms have almost the same performance in all other cases

Recent developments on the ALICE central Trigger processor

The ALI CE Central Trigger Processor has been constructed and tested, and will shortly be installed in the experimental area. In this review, we introduce the new developments in hardware and software, present a measurement of the minimum propagation time, and illustrate various trigger applications

Timing in the ALICE trigger system

In this paper we discuss trigger signals synchronisation and trigger input alignment in the ALICE trigger system. The synchronisation procedure adjusts the phase of the input signals with respect to the local Bunch Crossing (BC) clock and, indirectly, with respect to the LHC bunch crossing instant. The synchronisation delays are within one clock period: 0-25 ns. The alignment assures that the trigger signals originating from the same bunch crossing reach the processor logic in the same clock cycle. It is achieved by delaying signals by an appropriate number of full clock periods. We propose a procedure which will allow us to nd alignment delays during the system con guration, and to monitor them during the data taking

Identification of similar epitopes between SARS-CoV-2 and Bacillus Calmette-Guérin: potential for cross-reactive adaptive immunity

Objectives: Bacillus Calmette–Guérin (BCG) vaccination has been implicated in protection against SARS-CoV-2 and as a non-specific immunization method against the virus. We therefore decided to investigate T cell and B cell epitopes within the BCG Pasteur strain proteome for similarity to immunogenic peptides of SARS-CoV-2. Methods: We used a bioinformatic approach and analyzed the BCG-Pasteur proteome to identify similar peptides to established and novel SARS-CoV-2 T cell and B cell epitopes. Results: We found 112 BCG MHC-I restricted T cell epitopes similar to MHC-I restricted T cell SARS-CoV-2 epitopes and 690 BCG B cell epitopes similar to SARS-CoV-2 B cell epitopes. The SARS-CoV-2 T cell epitopes represented 16 SARS-CoV-2 proteins, the SARS-CoV-2 B cell epitopes represented 5 SARS-CoV-2 proteins, including the receptor binding domain of the spike glycoprotein. Conclusion: Altogether our results provide a mechanistic basis for the potential cross-reactive adaptive immunity that may exists between the two microorganisms

Expansion dynamics of Pb-Pb collisions at 40 A GeV/c viewed by negatively charged hadrons

In this paper we present results on transverse mass spectra and Hanbury-Brown and Twiss correlation functions of negatively charged hadrons, which are expected to be mostly negative pions, measured in Pb-Pb collisions at 40 A GeV/c beam momentum. Based on these data, the collision dynamics and the space-time extent of the system at the thermal freeze-out are studied over a centrality range corresponding to the most central 53% of the Pb--Pb inelastic cross section. Comparisons with freeze-out conditions of strange particles and HBT results from other experiments are discussed.Comment: 29 pages, 18 figure

The ALICE trigger electronics

The ALICE trigger system (TRG) consists of a Central Trigger Processor (CTP) and up to 24 Local Trigger Units (LTU) for each sub-detector. The CTP receives and processes trigger signals from trigger detectors and the outputs from the CTP are 3 levels of hardware triggers: L0, L1 and L2. The 24 sub-detectors are dynamically partitioned in up to 6 independent clusters. The trigger information is propagated through the LTUs to the Front-end electronics (FEE) of each sub-detector via LVDS cables and optical fibres. The trigger information sent from LTU to FEE can be monitored online for possible errors using the newly developed TTCit board. After testing and commissioning of the trigger system itself on the surface, the ALICE trigger electronics has been installed and tested in the experimental cavern with appropriate ALICE experimental software. Testing the Alice trigger system with detectors on the surface and in the experimental cavern in parallel is progressing very well. Currently one setup is used for testing on the surface; another is installed in experimental cavern. This paper describes the current status of ALICE trigger electronics, online error trigger monitoring and appropriate software for this electronics

Exploring Pompeii: discovering hospitality through research synergy

Hospitality research continues to broaden through an ever-increasing dialogue and alignment with a greater number of academic disciplines. This paper demonstrates how an enhanced understanding of hospitality can be achieved through synergy between archaeology, the classics and sociology. It focuses on classical Roman life, in particular Pompeii, to illustrate the potential for research synergy and collaboration, to advance the debate on hospitality research and to encourage divergence in research approaches. It demonstrates evidence of commercial hospitality activities through the excavation hotels, bars and taverns, restaurants and fast food sites. The paper also provides an example of the benefits to be gained from multidisciplinary analysis of hospitality and tourism