7,824 research outputs found
Enhancing R with Advanced Compilation Tools and Methods
I describe an approach to compiling common idioms in R code directly to
native machine code and illustrate it with several examples. Not only can this
yield significant performance gains, but it allows us to use new approaches to
computing in R. Importantly, the compilation requires no changes to R itself,
but is done entirely via R packages. This allows others to experiment with
different compilation strategies and even to define new domain-specific
languages within R. We use the Low-Level Virtual Machine (LLVM) compiler
toolkit to create the native code and perform sophisticated optimizations on
the code. By adopting this widely used software within R, we leverage its
ability to generate code for different platforms such as CPUs and GPUs, and
will continue to benefit from its ongoing development. This approach
potentially allows us to develop high-level R code that is also fast, that can
be compiled to work with different data representations and sources, and that
could even be run outside of R. The approach aims to both provide a compiler
for a limited subset of the R language and also to enable R programmers to
write other compilers. This is another approach to help us write high-level
descriptions of what we want to compute, not how.Comment: Published in at http://dx.doi.org/10.1214/13-STS462 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Slashdot, open news and informated media: exploring the intersection of imagined futures and web publishing technology
"In this essay, my interest is in how imagined media futures are implicated in the work of producing novel web publishing technology. I explore the issue through an account of the emergence of Slashdot, the tech news and discussion site that by 1999 had implemented a number of recommendation features now associated with social media and web 2.0 platforms. Specifically, I aim to understand the connection between the development of Slashdot’s influential content-management system (CMS) - an elaborate publishing infrastructure called “Slash” that allowed editors to choose reader submissions for publication and automatically distributed the work of moderating the comments sections among trusted users - and two distinct visions of a web-enabled transformation of media production.
Advanced Message Routing for Scalable Distributed Simulations
The Joint Forces Command (JFCOM) Experimentation Directorate (J9)'s recent Joint Urban Operations (JUO)
experiments have demonstrated the viability of Forces Modeling and Simulation in a distributed environment. The
JSAF application suite, combined with the RTI-s communications system, provides the ability to run distributed
simulations with sites located across the United States, from Norfolk, Virginia to Maui, Hawaii. Interest-aware
routers are essential for communications in the large, distributed environments, and the current RTI-s framework
provides such routers connected in a straightforward tree topology. This approach is successful for small to medium
sized simulations, but faces a number of significant limitations for very large simulations over high-latency, wide
area networks. In particular, traffic is forced through a single site, drastically increasing distances messages must
travel to sites not near the top of the tree. Aggregate bandwidth is limited to the bandwidth of the site hosting the
top router, and failures in the upper levels of the router tree can result in widespread communications losses
throughout the system.
To resolve these issues, this work extends the RTI-s software router infrastructure to accommodate more
sophisticated, general router topologies, including both the existing tree framework and a new generalization of the
fully connected mesh topologies used in the SF Express ModSAF simulations of 100K fully interacting vehicles.
The new software router objects incorporate the scalable features of the SF Express design, while optionally using
low-level RTI-s objects to perform actual site-to-site communications. The (substantial) limitations of the original
mesh router formalism have been eliminated, allowing fully dynamic operations. The mesh topology capabilities
allow aggregate bandwidth and site-to-site latencies to match actual network performance. The heavy resource load at
the root node can now be distributed across routers at the participating sites
21st Century Simulation: Exploiting High Performance Computing and Data Analysis
This paper identifies, defines, and analyzes the limitations imposed on Modeling and Simulation by outmoded
paradigms in computer utilization and data analysis. The authors then discuss two emerging capabilities to
overcome these limitations: High Performance Parallel Computing and Advanced Data Analysis. First, parallel
computing, in supercomputers and Linux clusters, has proven effective by providing users an advantage in
computing power. This has been characterized as a ten-year lead over the use of single-processor computers.
Second, advanced data analysis techniques are both necessitated and enabled by this leap in computing power.
JFCOM's JESPP project is one of the few simulation initiatives to effectively embrace these concepts. The
challenges facing the defense analyst today have grown to include the need to consider operations among non-combatant
populations, to focus on impacts to civilian infrastructure, to differentiate combatants from non-combatants,
and to understand non-linear, asymmetric warfare. These requirements stretch both current
computational techniques and data analysis methodologies. In this paper, documented examples and potential
solutions will be advanced. The authors discuss the paths to successful implementation based on their experience.
Reviewed technologies include parallel computing, cluster computing, grid computing, data logging, OpsResearch,
database advances, data mining, evolutionary computing, genetic algorithms, and Monte Carlo sensitivity analyses.
The modeling and simulation community has significant potential to provide more opportunities for training and
analysis. Simulations must include increasingly sophisticated environments, better emulations of foes, and more
realistic civilian populations. Overcoming the implementation challenges will produce dramatically better insights,
for trainees and analysts. High Performance Parallel Computing and Advanced Data Analysis promise increased
understanding of future vulnerabilities to help avoid unneeded mission failures and unacceptable personnel losses.
The authors set forth road maps for rapid prototyping and adoption of advanced capabilities. They discuss the
beneficial impact of embracing these technologies, as well as risk mitigation required to ensure success
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