Richard Fujimoto's research while affiliated with Georgia Institute of Technology and other places

Publications (229)

Article
Recognised as an important concern in mobile, cloud, and high performance computing, the power and energy consumed by computing applications is growing in importance across an increasingly broad range of areas. The importance of this topic to the modelling and simulation community is discussed. Key underlying concepts concerning power and energy co...
Article
Computer simulations are widely used to design and evaluate air traffic systems. A fast time simulation capability is essential to effectively explore the consequences of decisions in airspace design, air traffic management, and operations. A parallel simulation approach is proposed to accelerate fast time simulation of air traffic networks that ex...
Conference Paper
This study assesses feasibility aspects of using a real-time data-driven transportation simulation model to evaluate and visualize network performance indices to provide dynamic operational feedback in a real world environment, in a big data context. A hybrid traffic simulation model, consisting of a mix of preset and real-time data-driven intersec...
Conference Paper
Many runs of a computer simulation are needed to model uncertainty and evaluate alternate design choices. Such an ensemble of runs often contains many commonalities among the different individual runs. Simulation cloning is a technique that capitalizes on this fact to reduce the amount of computation required by the ensemble. Granular cloning is pr...
Conference Paper
The question of the energy consumed by synchronization algorithms for distributed simulation programs is addressed. The concept of zero energy synchronization is introduced wherein a distributed simulation program incurs no additional energy cost for synchronization. A theoretical approach to achieving zero energy synchronization using an oracle is...
Article
In current study, a mechanism to extract traffic related information such as congestion and incidents from textual data from the internet is proposed. The current source of data is Twitter. As the data being considered is extremely large in size automated models are developed to stream, download, and mine the data in real-time. Furthermore, if any...
Article
Full-text available
Congestion-induced delays and pollution in modern transportation systems remain formidable impediments to the sustainable growth of our cities. Next generation Intelligent Transportation Systems (ITS) will attack these problems by relying on extensive in-vehicle sensing, crowd-sourced data, ubiquitous computing, and communications to augment existi...
Chapter
This chapter is about the history of the Time Warp algorithm and optimistic approaches to parallel discrete event simulation. It concentrates on the early history from our personal perspective as active developers of the ideas over several decades.
Chapter
Computing and communication technologies have advanced rapidly in the last decade. M&S has not yet fully realized the potential and opportunities afforded by technologies such as mobile and ubiquitous computing, big data, the Internet of Things, cloud computing, and modern supercomputer architectures. This has kept M&S from achieving its fullest po...
Conference Paper
Energy and power consumption have become important concerns for many computing systems ranging from embedded and mobile systems operating on battery-powered devices to high performance and cloud computing applications running on supercomputers and in data centers. To date, only a limited amount of work has considered power consumption in parallel a...
Article
Simulation cloning involves expediting a simulation by sharing computational results among different sample paths. It resembles the idea of splitting, which is widely researched in rare event simulation, as splitting techniques also produce clones when a sample path reaches a certain state. In this paper, we consider the use of simulation cloning f...
Article
Power and energy consumption are important concerns in the design of high performance and mobile computing systems, but have not been widely considered in the design of parallel and distributed simulations. The importance of these factors is discussed and metrics for power and energy overhead in parallel and distributed simulations are proposed. Fa...
Article
Efforts to address operational issues in transportation have been the focus of many research efforts. A number of these efforts were geared toward developing microscopic traffic simulation models to accurately represent the complex and dynamic operation of a transportation network. One of the challenges with such models is that they do not always a...
Article
Congestion is a major issue in transportation sector. As professionals in the transportation field are increasingly exploring new solutions to alleviate traffic congestion, interest in the use of on-line simulation as a tool for estimating metrics of the traffic network for use in real-time operations has grown. The goal of the on-line simulation i...
Conference Paper
Vehicle trajectory or route prediction is useful in online, data-driven transportation simulation to predict future traffic patterns and congestion, among other uses. The various approaches to route prediction have varying degrees of data required to predict future vehicle trajectories. Three approaches to vehicle trajectory prediction, along with...
Conference Paper
An energy profile indicates the amount of energy consumed by different parts of a parallel or distributed simulation program. Creating energy profiles is not straightforward because high precision, low overhead energy measurement mechanisms may not be available, and it is not straightforward to determine the amount of energy consumed by different h...
Article
The parallel and distributed simulation field has evolved and grown from its origins in the 1970s and 1980s and remainsanactivefieldofresearchtothis day.Abrief overview of researchinthefieldispresented. Future research topics are explored including areas such as problem-driven simulation of large-scale systems and complex networks, exploitation of...
Article
Full-text available
Many Dynamic Data-Driven Application Systems (DDDAS) use replicated simulations to project possible future system states. In many cases there are substantial similarities among these different replications. In other cases output statistics are independent of certain simulation computations. This paper explores computational methods to exploit these...
Conference Paper
Full-text available
The National Modeling and Simulation Coalition (NMSC) is interested in a national research agenda that enables the convergence of domain specific modeling and simulation (M&S) approaches towards a common discipline to foster reuse and dissemination of research results. This panel evaluates the various views on such an effort from experts in the dom...
Conference Paper
Power and energy consumption are important concerns in the design of high performance, embedded and mobile computing systems but have not been widely considered in the design of parallel and distributed simulations. The importance of these factors is discussed in the context of mobile online distributed simulations. Preliminary results are reported...
Article
Full-text available
The primary focus of computer simulation in transportation engineering has been to model individual systems using modeling software packages designed for the specific system under investigation. However, this limits the ability to explore interactions between multiple disparate transportation systems in a dynamic modeling environment. To address th...
Article
We propose a data structure that stores previously observed vehicle paths in a given area in order to predict the forward trajectory of an observed vehicle at any stage. Incomplete vehicle trajectories are conditioned against in a Past Tree, to predict future trajectories in another tree structure - a Future Tree. Many use cases in transportation s...
Article
Full-text available
Tracking the movement of vehicles in urban environments using fixed position sensors, mobile sensors, and crowd-sourced data is a challenging but important problem in applications such as law enforcement and defense. A dynamic data driven application system (DDDAS) is described to track a vehicle's movements by repeatedly identifying the vehicle un...
Article
With the growing use of mobile devices, power aware algorithms have become essential. Data distribution management (DDM) is an approach to disseminate information that was proposed in the High Level Architecture (HLA) for modeling and simulation. This paper explores the power consumption of mobile devices used by pedestrians in an urban environment...
Article
The widespread deployment of sensors, computers, and communications in vehicles and roadways is creating new challenges and opportunities to effectively exploit the wealth of real-time data and information that is now becoming increasingly available. In this paper the authors capitalize on these rapid technological advancements using a technique te...
Conference Paper
Ad hoc distributed simulation, a methodology for embedded online simulation, has been studied for the steady-state simulation of open queueing networks. However, for most online simulation applications, the capability of a simulation approach to respond to system dynamics is at least as important as the performance in steady-state analysis. Hence,...
Conference Paper
Scale-free networks have received much attention in recent years due to their prevalence in many important applications such as social networks, biological systems, and the Internet. We consider the use of conservative parallel discrete event simulation techniques in network simulation applications involving scale-free networks. An analytical model...
Article
Microscopic traffic simulation tools are increasingly being employed as an integral part of modeling vehicular traffic and pedestrian activity. However, the complexity of pedestrians’ behaviors and their interactions with the various components of the traffic network is commonly under-represented in simulation models, resulting in potentially misle...
Conference Paper
Full-text available
We propose a new automatic program inversion method for imperative programs that contain loops. In particular, given a loop that produces an output state given a particular input state, our method can synthesize an inverse loop that reconstructs the input state given the original loop's output state. The synthesis process consists of two major comp...
Conference Paper
Despite recent technological advancements in alleviating roadway congestion, there is still a considerable amount of time and fuel wasted by travelers. In searching for solutions to mitigate congestion, a number of research efforts have been geared toward developing simulation tools to provide real-time performance measures. One of the challenges o...
Conference Paper
It has been a decade since the Workshop on Grand Challenge for Modeling & Simulation (M&S) was held at Dagstuhl in Germany (www.dagstuhl.de/02351). Grand challenges provide a critical focal point for research and development and can potentially create the critical mass needed to bring substantial transformation and benefit to a community. The Works...
Article
Ad hoc distributed simulation is an approach to predicting future states of operational systems. It is based on embedding online simulations into a sensor network and adding communication and synchronization among the simulators. While prior work focused on this approach in the context of online management of transportation systems, this paper desc...
Article
The master/worker (MW) paradigm can be used as an approach to parallel discrete event simulation (PDES) on metacomputing systems. MW PDES applications incur overheads not found in conventional PDES executions executing on tightly coupled machines. We introduce four optimization techniques in MW PDES systems on public resource and desktop grid infra...
Conference Paper
Full-text available
Program inversion has been successfully applied to several areas such as optimistic parallel discrete event simulation (OPDES) and reverse debugging. This paper introduces a new program inversion algorithm for imperative languages, and focuses on handling arbitrary control flows and basic operations. By building a value search graph that represents...
Article
Full-text available
The Dynamic Data Driven Application Systems (DDDAS) concept is examined in the context of monitoring and managing surface transportation systems in day-to-day and emergency scenarios. An approach to predicting future system states termed ad hoc distributed simulations is described. This approach uses on-line distributed simulation models that can i...
Article
Innovation and the generation of new knowledge are fundamental research goals. As such, proficiency in these areas is essential to becoming a successful researcher. Yet, although a principal goal of graduate school is to train students to become effective researchers, innovation is seldom explicitly discussed. The goal of this article is to fill th...
Article
Full-text available
An ad hoc distributed simulation is a collection of online simulators embedded in a sensor network that communicate and synchronize among themselves. Each simulator is driven by sensor data and state predictions from other simulators. Previous work has examined this approach in transportation systems and queueing networks. Ad hoc distributed simula...
Article
Full-text available
Interest management is essential for reducing communication overhead by filtering irrelevant messages in mobile distributed systems. Interest management schemes developed for distributed simulation systems such as those based on HLA can be applied to mobile systems. Sort-based schemes have been proposed and shown to yield good performance. When usi...
Conference Paper
Full-text available
We introduce Backstroke, a new open source framework for the automatic generation of reverse code for functions written in C++. Backstroke enables reverse computation for optimistic parallel discrete event simulations. It is built using the ROSE open-source compiler infrastructure, and handles complex C++ features including pointers and pointer typ...
Article
A recent DMSO (Defense Modeling and Simulation Office) initiative resulted in a new RTI design and build effort. This paper describes the design constructs used in the RTI 2.0 architecture and the driving principles used throughout the design process. Key architectural features are identified and analyzed in terms of meeting the RTI's set of requir...
Conference Paper
Ad hoc distributed simulations are constructed by embedding online simulations into a network of sensors. Recent work examining the effectiveness of ad hoc distributed simulations in modeling open queueing networks has been limited to a specific network configuration. This paper examines the accuracy of the ad hoc approach more broadly for open que...
Conference Paper
Full-text available
Transportation professionals are increasingly exploring multi-pronged solutions to alleviate traffic congestion. Real-time information systems for travelers and facility managers are one approach that has been the focus of many recent efforts. Real-time performance information can facilitate more efficient roadway usage and operations. Toward this...
Conference Paper
Ad hoc distributed simulation is an approach to predict future states of operational systems. It is based on embedding on-line simulations into a sensor network and adding communication and synchronization among the simulators. While prior work focused on this approach in the context of online management of transportation systems, this paper descri...
Article
Cloud computing offers the ability to provide parallel and distributed simulation services remotely to users through the Internet. Services hosted within the "cloud" can potentially incur processing delays due to load sharing among other active services, and can cause optimistic simulation protocols to perform poorly. This article discusses problem...
Article
Full-text available
Cloud computing offers the ability to transparently provide computing services remotely to users through the Internet, freeing them of the burdens associated with managing computing resources and facilities. It offers the potential to make parallel and distributed simulation capabilities much more widely accessible to users who are not experts in t...
Conference Paper
On-line in-vehicle traffic simulation has been proposed as a means to provide predictions of future states of a traffic network based on current traffic conditions. The area covered by an in-vehicle simulation may change dynamically during the vehicle's journey. This paper is concerned with the issue of initializing the state of new regions that ar...
Conference Paper
Full-text available
A testbed for evaluation of online distributed simulations of transportation system infrastructures is described that includes a modest portion of an urban road network in the midtown region of Atlanta, Georgia. The testbed includes sensors, servers, wireless communications, and mobile transportation simulations configured to model the testbed regi...
Conference Paper
Traffic congestion is a source of significant economic and social costs in urban areas. Intelligent Transportation Systems (ITS) are a promising means to help alleviate congestion by utilizing advanced sensing, computing, and communication technologies. This paper investigates a basic ITS framework - Advanced Traveler Information System (ATIS) - us...
Chapter
This paper reports the main results of a peer study on future trends in distributed simulation and distributed virtual environments. The peer study was based on the opinions of more than 60 experts which were collected by means of a survey and personal interviews. The survey collected opinions concerning the current state-of-the-art, relevance, and...
Conference Paper
The master/worker (MW) paradigm can be used to implement parallel discrete event simulations (PDES) on metacomputing systems. MW PDES applications incur overheads not found in conventional PDES executions executing on tightly coupled machines. We introduce four techniques for reducing these overheads on public resource and desktop grid infrastructu...
Article
An ad hoc distributed dynamic data-driven simulation is a collection of autonomous online simulations brought together to model an operational system. They offer the potential of increased accuracy, responsiveness, and robustness compared to centralized approaches. They differ from conventional distributed simulations in that they are created botto...
Article
There has been increasing interest in building an information infrastructure for mobile vehicles in surface transportation systems that principally rely on vehicle-to-vehicle (v2v) communications. The various network architectures proposed for this purpose have unique characteristics that distinguish them from other systems. However, only a limited...
Conference Paper
Cloud computing offers the potential to make parallel discrete event simulation capabilities more widely accessible to users who are not experts in this technology and do not have ready access to high performance computing equipment. Services hosted within the ldquocloudrdquo can potentially incur processing delays due to load sharing among other a...
Conference Paper
Full-text available
This paper reports main results of a peer study on future trends in distributed simulation and distributed virtual environments (Strassburger et al. 2008). The peer study was based on the opinions of more than 60 experts which were collected by means of a survey and personal interviews. The survey collected opinions concerning the current state-of-...
Conference Paper
Congestion is one of the major issues facing today's transportation sector. Recent efforts have been geared to- ward providing traffic information to travelers, to facili- tate better travel decisions, and transportation facility managers, to allow them to better manage traffic opera- tions. Currently, real-time traffic information is primarily lim...
Conference Paper
Remote network emulation is an approach that utilizes a remote parallel simulator to improve the scale and accuracy of network emulation for general users with no local access to high performance computing facilities. The remote network emulation approach involves using a large scale detailed packet level simulation at a remote site in conjunction...
Article
Full-text available
The application of parallel and distributed simulation techniques is often limited by the amount of parallelism available in the model. This holds true for large-scale cell-biological simulations, a field that has emerged as data and knowledge concerning these systems increases and??biologists call for tools to guide wet-lab experimentation. A prom...
Article
Many of today's military services and applications run on geographically distributed sites. Be-fore these services and applications can be deployed in an actual network, they need to be tested and evaluated under realistic scenarios with many unpredictable factors. Existing experimental tools cannot meet the requirements for scale, accuracy and tim...
Article
The high-level architecture (HLA) standard developed by the Department of Defense in the United States is a key technology to perform distributed simulation. Inside the HLA framework, many different simulators (termed federates) may be interconnected to create a single more complex simulator (federation). Data distribution management (DDM) is an op...
Article
As data and knowledge about cell-biological systems increases so does the need for simulation tools to support a hypothesis driven wet-lab experimentation. Discrete event simulation has received a lot of attention lately, however, often its application is hampered by its lack on performance. One solution are parallel, distributed approaches, howeve...
Chapter
Research and development efforts in the parallel and distributed simulation field over the last 15 years has progressed, largely independently, in two separate camps: the largely academic high performance parallel and distributed (discrete event) simulation (PADS) community, and the DoD-centered distributed interactive simulation (DIS) community. T...
Conference Paper
Network emulation has been widely used to aid in the development and evaluation of real time applications. Traditional emulation tools based on a single node machine or a cluster of machines cannot satisfy today's requirements for testing real time applications distributed over wide area networks. ROSENET is a novel network emulation system that ex...
Conference Paper
Utilizing desktop grid infrastructures is challenging for parallel discrete event simulation (POES) codes due to characteristics such as inter-process messaging, restricted execution, and overall lower concurrency than typical volunteer computing projects. The Aurora2 system uses an approach that simultaneously provides both replicated execution su...
Chapter
The excessive amount of time necessary to complete large-scale discrete-event simulations of complex systems such as telecommunication networks, transportation systems, and multiprocessor computers continues to plague researchers and impede progress in many important domains. Parallel discrete-event simulation techniques offer an attractive solutio...
Conference Paper
Full-text available
Current research in applying the Dynamic Data Driven Application Systems (DDDAS) concept to monitor and manage surface transportation systems in day-to-day and emergency scenarios is described. This work is focused in four, tightly coupled areas. First, a novel approach to predicting future system states termed ad hoc distributed simulations has be...
Conference Paper
A study is presented in applying optimistic parallel discrete event simulation techniques using reverse execution to perform instruction-level simulations of distributed memory multi-processor systems. A static program analysis approach is described to optimize pre-processed simulated applications in order to remove certain overheads associated wit...
Article
New discrete-event formulations of physics simulation models are emerging that can outperform traditional time-stepped models, especially in simulations containing multiple timescales. Detailed simulation of the Earth's magnetosphere, for example, requires execution of sub-models that operate at timescales that differ by orders of magnitude. In con...
Conference Paper
Full-text available
An ad hoc distributed simulation is a collection of autonomous on-line simulations brought together to model an operational system. They offer the potential of increased accuracy, responsiveness, and robustness compared to centralized approaches. They differ from conventional distributed simulations in that they are created bottom-up rather than to...
Article
Full-text available
Progress in space physics has always been strongly dependent on analysis of in situ spacecraft measurements. However, the vast majority of spacecraft data go unexplored and with upcoming multi-spacecraft NASA missions (THEMIS, MMS, etc.) the growing size of data promises to outpace the ability of scientists to analyze them. There are several NASA f...
Conference Paper
Many of today's military services and applications run on geographically distributed sites and need to be tested and evaluated under realistic scenarios with many unpredictable factors. A remote network emulation framework called ROSENET is proposed that can meet this requirement by using a remote parallel simulation server to model the wide area n...