Discrete Event Simulation (DES) is a widely used technique in which the state of the simulator is updated by events happening at discrete points in time (hence the name). DES is used to model and analyze many kinds of systems, including computer architectures, communication networks, street traffic, and others. Parallel and Distributed Simulation (PADS) aims at improving the efficiency of DES by partitioning the simulation model across multiple processing elements, in order to enable larger and or more detailed studies to be carried out. The interest on PADS is increasing since the widespread availability of multicore processors and affordable high performance computing clusters. However, designing parallel simulation models requires considerable expertise, the result being that PADS techniques are not as widespread as they could be. In this paper we describe ErlangTW, a parallel simulation middleware based on the Time Warp synchronization protocol. ErlangTW is entirely written in Erlang, a concurrent, functional programming language specifically targeted at building distributed systems. We argue that writing parallel simulation models in Erlang is considerably easier than using conventional programming languages. Moreover, ErlangTW allows simulation models to be executed either on single-core, multicore and distributed computing architectures. We describe the design and prototype implementation of ErlangTW, and report some preliminary performance results on multicore and distributed architectures using the well known PHOLD benchmark.
Over the years, many PADS tools, languages and middlewares have been proposed (a comprehensive but somewhat outdated list can be found in @cite_23 ); in this section we highlight some of the most significant results with specific attention to the implementations of the Time Warp synchronization mechanism.
@cite_23
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In this paper we deal with the impact of multi and many-core processor architectures on simulation. Despite the fact that modern CPUs have an increasingly large number of cores, most softwares are still unable to take advantage of them. In the last years, many tools, programming languages and general methodologies have been proposed to help building scalable applications for multi-core architectures, but those solutions are somewhat limited. Parallel and distributed simulation is an interesting application area in which efficient and scalable multi-core implementations would be desirable. In this paper we investigate the use of the Go Programming Language to implement optimistic parallel simulations based on the Time Warp mechanism. Specifically, we describe the design, implementation and evaluation of a new parallel simulator. The scalability of the simulator is studied when in presence of a modern multi-core CPU and the effects of the Hyper-Threading technology on optimistic simulation are analyzed. Abstract The ability to access large amounts of de-identified clinical data would facilitate epidemiologic and retrospective research. Previously described de-identification methods require knowledge of natural language processing or have not been made available to the public. We take advantage of the fact that the vast majority of proper names in pathology reports occur in pairs. In rare cases where one proper name is by itself, it is preceded or followed by an affix that identifies it as a proper name (Mrs., Dr., PhD). We created a tool based on this observation using substitution methods that was easy to implement and was largely based on publicly available data sources. We compiled a Clinical and Common Usage Word (CCUW) list as well as a fairly comprehensive proper name list. Despite the large overlap between these two lists, we were able to refine our methods to achieve accuracy similar to previous attempts at de-identification. Our method found 98.7 of 231 proper names in the narrative sections of pathology reports. Three single proper names were missed out of 1001 pathology reports (0.3 , no first name last name pairs). It is unlikely that identification could be implied from this information. We will continue to refine our methods, specifically working to improve the quality of our CCUW and proper name lists to obtain higher levels of accuracy. A new form of document coupling called co-citation is defined as the frequency with which two documents are cited together. The co-citation frequency of two scientific papers can be determined by comparing lists of citing documents in the Science Citation Index and counting identical entries. Networks of co-cited papers can be generated for specific scientific specialties, and an example is drawn from the literature of particle physics. Co-citation patterns are found to differ significantly from bibliographic coupling patterns, but to agree generally with patterns of direct citation. Clusters of co-cited papers provide a new way to study the specialty structure of science. They may provide a new approach to indexing and to the creation of SDI profiles. Abstract In recent years a considerable effort has been spent by research and industrial communities in the digitalization of production environments with the main objective of achieving a new automation paradigm, more flexible, responsive to changes, and safe. This paper presents the architecture, and discusses the benefits, of a distributed middleware prototype supporting a new generation of smart-factory-enabled applications with special attention paid to simulation tools. Devised within the scope of MAYA EU project, the proposed platform aims at being the first solution capable of empowering shop-floor Cyber-Physical-Systems (CPSs), providing an environment for their Digital Twin along the whole plant life-cycle. The platform implements a microservice IoT-Big Data architecture supporting the distributed publication of multidisciplinary simulation models, managing in an optimized way streams of data coming from the shop-floor for real-digital synchronization, ensuring security and confidentiality of sensible data.