Stationarity, soft ergodicity, and entropy in relativistic systems

Recent molecular dynamics simulations show that a dilute relativistic gas equilibrates to a Juettner velocity distribution if ensemble velocities are measured simultaneously in the observer frame. The analysis of relativistic Brownian motion processes, on the other hand, implies that stationary one-particle distributions can differ depending on the underlying time-parameterizations. Using molecular dynamics simulations, we demonstrate how this relativistic phenomenon can be understood within a deterministic model system. We show that, depending on the time-parameterization, one can distinguish different types of soft ergodicity on the level of the one-particle distributions. Our analysis further reveals a close connection between time parameters and entropy in special relativity. A combination of different time-parameterizations can potentially be useful in simulations that combine molecular dynamics algorithms with randomized particle creation, annihilation, or decay processes.Comment: 4 page

NMR-Mpar: A Fault-Tolerance Approach for Multi-Core and Many-Core Processors

International audienceMulti-core and many-core processors are a promising solution to achieve high performance 6 by maintaining a lower power consumption. However, the degree of miniaturisation make 7 them more sensitive to soft-errors. To improve the system reliability, this work proposes a 8 fault-tolerance approach based on redundancy and partitioning principles called NMR-MPar: 9 N-Modular Redundancy and M-Partitions. By combining both principles, this approach allows 10 multi/many-core processors to perform critical functions in mixed-criticality systems. Benefiting of 11 the capabilities of these devices, NMR-MPar creates different partitions that perform independent 12 functions. For critical functions, it is proposed that N partitions with the same configuration 13 participate of a N-Modular Redundancy system. In order to validate the approach, a case study 14 is implemented on the KALRAY MPPA-256 many-core processor running two parallel benchmark 15 applications. Traveling Salesman Problem and Matrix Multiplication applications were selected to test 16 different device’s resources. The effectiveness of NMR-MPar is assessed by Software Implemented 17 Fault-Injection. For evaluation purposes, it is considered that the system is intended to be used in 18 avionics. Results show the improvement of the application reliability in two orders of magnitude 19 when implementing NMR-MPar on the system. Finally, ththis work opens the possibility to use 20 massive parallelism for dependable applications in embedded systems

Parallelization of Continuous Verified Global Optimization

An algorithm for verified continuous global optimization, based on interval arithmetic, has been designed by Hansen. This algorithm is of the Branch&Bound type and has an exponential complexity; it thus deserves parallelization. However, this is not straightforward: indeed, it is impossible to predict at compile time which sub-problems will be treated and thus load-balancing can only be performed dynamically. Our proposal for the parallelization of Hansen's algorithm consists in creating a lightweight process or thread to explore each subinterval and in beginning its execution immediately after its creation. This strategy provides a high level of speculation and enables to virtualize the architecture, since designing the algorithm and porting it to a new architecture are now distinct activities; the load-balancing is also a separate activity. The parallel execution support PM2, developped in Lille and Lyon, handles the concurrent execution of threads and their creation, migr..

ParaMiner: a Generic Pattern Mining Algorithm for Multi-Core Architectures

International audienceIn this paper, we present Para Miner which is a generic and parallel algorithm for closed pattern mining. Para Miner is built on the principles of pattern enumeration in strongly accessible set systems. Its efficiency is due to a novel dataset reduction technique (that we call EL-reduction), combined with novel technique for performing dataset reduction in a parallel execution on a multi-core architecture. We illustrate Para Miner's genericity by using this algorithm to solve three different pattern mining problems: the frequent itemset mining problem, the mining frequent connected relational graphs problem and the mining gradual itemsets problem. In this paper, we prove the soundness and the completeness of Para Miner. Furthermore, our experiments show that despite being a generic algorithm, Para Miner can compete with specialized state of the art algorithms designed for the pattern mining problems mentioned above. Besides, for the particular problem of gradual itemset mining, Para Miner outperforms the state of the art algorithm by two orders of magnitude

Estimation of the effective orientation of the SHG source in primary cortical neurons

In this paper we provide, for the first time to our knowledge, the effective orientation of the SHG source in cultured cortical neuronal processes in vitro. This is done by the use of the polarization sensitive second harmonic generation (PSHG) imaging microscopy technique. By performing a pixel-level resolution analysis we found that the SHG dipole source has a distribution of angles centered at θe =33.96°, with a bandwidth of ∆θe = 12.85°. This orientation can be related with the molecular geometry of the tubulin heterodimmer contained in microtubules.This work is supported by the Generalitat de Catalunya and by the Spanish government grant TEC2006-12654. Authors also acknowledge The Centre for Innovacio i Desenvolupament Empresarial - CIDEM (RDITSCON07-1-0006), Grupo Ferrer and the European Regional Development Fund. This research has been partially supported by Fundació Cellex Barcelona.Peer reviewe