3,975 research outputs found
An open interface for parallelization of traffic simulation
In this paper, we present the implementation of a parallel road traffic simulation using the concept of Lane Cut Points (LCPs) in the Spider programming environment. LCPs are storage buffers inserted into lane data structures at the road network partition edges. Vehicles enter a partition at the edges from an LCP and exit a partition edge into an LCP at the end of every simulation step. Spider, a parallel programming environment, which runs on PVM, coordinates the execution of the parallel traffic simulation
Enabling Distributed Simulation of OMNeT++ INET Models
Parallel and distributed simulation have been extensively researched for a
long time. Nevertheless, many simulation models are still executed
sequentially. We attribute this to the fact that many of those models are
simply not capable of being executed in parallel since they violate particular
constraints. In this paper, we analyze the INET model suite, which enables
network simulation in OMNeT++, with regard to parallelizability. We uncovered
several issues preventing parallel execution of INET models. We analyzed those
issues and developed solutions allowing INET models to be run in parallel. A
case study shows the feasibility of our approach. Though there are parts of the
model suite that we didn't investigate yet and the performance can still be
improved, the results show parallelization speedup for most configurations. The
source code of our implementation is available through our web site at
code.comsys.rwth-aachen.de.Comment: Published in: A. F\"orster, C. Sommer, T. Steinbach, M. W\"ahlisch
(Eds.), Proc. of 1st OMNeT++ Community Summit, Hamburg, Germany, September 2,
2014, arXiv:1409.0093, 201
Tangos: the agile numerical galaxy organization system
We present Tangos, a Python framework and web interface for database-driven
analysis of numerical structure formation simulations. To understand the role
that such a tool can play, consider constructing a history for the absolute
magnitude of each galaxy within a simulation. The magnitudes must first be
calculated for all halos at all timesteps and then linked using a merger tree;
folding the required information into a final analysis can entail significant
effort. Tangos is a generic solution to this information organization problem,
aiming to free users from the details of data management. At the querying
stage, our example of gathering properties over history is reduced to a few
clicks or a simple, single-line Python command. The framework is highly
extensible; in particular, users are expected to define their own properties
which tangos will write into the database. A variety of parallelization options
are available and the raw simulation data can be read using existing libraries
such as pynbody or yt. Finally, tangos-based databases and analysis pipelines
can easily be shared with collaborators or the broader community to ensure
reproducibility. User documentation is provided separately.Comment: Clarified various points and further improved code performance;
accepted for publication in ApJS. Tutorials (including video) at
http://tiny.cc/tango
Hybrid-parallel sparse matrix-vector multiplication with explicit communication overlap on current multicore-based systems
We evaluate optimized parallel sparse matrix-vector operations for several
representative application areas on widespread multicore-based cluster
configurations. First the single-socket baseline performance is analyzed and
modeled with respect to basic architectural properties of standard multicore
chips. Beyond the single node, the performance of parallel sparse matrix-vector
operations is often limited by communication overhead. Starting from the
observation that nonblocking MPI is not able to hide communication cost using
standard MPI implementations, we demonstrate that explicit overlap of
communication and computation can be achieved by using a dedicated
communication thread, which may run on a virtual core. Moreover we identify
performance benefits of hybrid MPI/OpenMP programming due to improved load
balancing even without explicit communication overlap. We compare performance
results for pure MPI, the widely used "vector-like" hybrid programming
strategies, and explicit overlap on a modern multicore-based cluster and a Cray
XE6 system.Comment: 16 pages, 10 figure
QarSUMO: A Parallel, Congestion-optimized Traffic Simulator
Traffic simulators are important tools for tasks such as urban planning and
transportation management. Microscopic simulators allow per-vehicle movement
simulation, but require longer simulation time. The simulation overhead is
exacerbated when there is traffic congestion and most vehicles move slowly.
This in particular hurts the productivity of emerging urban computing studies
based on reinforcement learning, where traffic simulations are heavily and
repeatedly used for designing policies to optimize traffic related tasks.
In this paper, we develop QarSUMO, a parallel, congestion-optimized version
of the popular SUMO open-source traffic simulator. QarSUMO performs high-level
parallelization on top of SUMO, to utilize powerful multi-core servers and
enables future extension to multi-node parallel simulation if necessary. The
proposed design, while partly sacrificing speedup, makes QarSUMO compatible
with future SUMO improvements. We further contribute such an improvement by
modifying the SUMO simulation engine for congestion scenarios where the update
computation of consecutive and slow-moving vehicles can be simplified.
We evaluate QarSUMO with both real-world and synthetic road network and
traffic data, and examine its execution time as well as simulation accuracy
relative to the original, sequential SUMO
Distributed Hybrid Simulation of the Internet of Things and Smart Territories
This paper deals with the use of hybrid simulation to build and compose
heterogeneous simulation scenarios that can be proficiently exploited to model
and represent the Internet of Things (IoT). Hybrid simulation is a methodology
that combines multiple modalities of modeling/simulation. Complex scenarios are
decomposed into simpler ones, each one being simulated through a specific
simulation strategy. All these simulation building blocks are then synchronized
and coordinated. This simulation methodology is an ideal one to represent IoT
setups, which are usually very demanding, due to the heterogeneity of possible
scenarios arising from the massive deployment of an enormous amount of sensors
and devices. We present a use case concerned with the distributed simulation of
smart territories, a novel view of decentralized geographical spaces that,
thanks to the use of IoT, builds ICT services to manage resources in a way that
is sustainable and not harmful to the environment. Three different simulation
models are combined together, namely, an adaptive agent-based parallel and
distributed simulator, an OMNeT++ based discrete event simulator and a
script-language simulator based on MATLAB. Results from a performance analysis
confirm the viability of using hybrid simulation to model complex IoT
scenarios.Comment: arXiv admin note: substantial text overlap with arXiv:1605.0487
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