Volume visualization of time-varying data using parallel, multiresolution and adaptive-resolution techniques

This paper presents a parallel rendering approach that allows high-quality visualization of large time-varying volume datasets. Multiresolution and adaptive-resolution techniques are also incorporated to improve the efficiency of the rendering. Three basic steps are needed to implement this kind of an application. First we divide the task through decomposition of data. This decomposition can be either temporal or spatial or a mix of both. After data has been divided, each of the data portions is rendered by a separate processor to create sub-images or frames. Finally these sub-images or frames are assembled together into a final image or animation. After developing this application, several experiments were performed to show that this approach indeed saves time when a reasonable number of processors are used. Also, we conclude that the optimal number of processors is dependent on the size of the dataset used

[[alternative]]Reaserch of Frame Synchronisation Algorithm for the PC Cluster of CAVE System

計畫編號：NSC90-2213-E032-015研究期間：200108~200207研究經費：700,000[[sponsorship]]行政院國家科學委員

A PC Cluster High-Fidelity Mobile Crane Simulator

[[abstract]]The mobile crane simulator is a project sponsored by Employment and Vocational Training Administration, Council of Labor Affair, Executive Yuan, Taiwan, to build a safe device for training and licensing. This paper presents the principle and mechanism to build a high-fidelity interactive visual simulator on a cluster of PCs. The implemented mobile crane simulator uses the peer-to-peer architecture with the push and pull mechanism to achieve the parallelism among distributed tasks. A distributive simulation socket, called Communication Backbone(CB), is adopted to integrate the functional tasks of the mobile crane simulator in a PC clustering environment. With CB, tasks of the simulated mobile crane are executed as standalone applications and seamlessly communicate with each other through CB. Finally, the system response rate of the implemented mobile crane simulator achieves 16 times per second which is larger than human acceptable perception rate as suggested by the human factors studies.[[abstract]]The mobile crane simulator is a project sponsored by Employment and Vocational Training Administration, Council of Labor Affair, Executive Yuan, Taiwan, to build a safe device for training and licensing. This paper presents the principle and mechanism to build a high-fidelity interactive visual simulator on a cluster of PCs. The implemented mobile crane simulator uses the peer-to-peer architecture with the push and pull mechanism to achieve the parallelism among distributed tasks. A distributive simulation socket, called Communication Backbone(CB), is adopted to integrate the functional tasks of the mobile crane simulator in a PC clustering environment. With CB, tasks of the simulated mobile crane are executed as standalone applications and seamlessly communicate with each other through CB. Finally, the system response rate of the implemented mobile crane simulator achieves 16 times per second which is larger than human acceptable perception rate as suggested by the human factors studies

Mixing multi-core CPUs and GPUs for scientific simulation software

Recent technological and economic developments have led to widespread availability of multi-core CPUs and specialist accelerator processors such as graphical processing units (GPUs). The accelerated computational performance possible from these devices can be very high for some applications paradigms. Software languages and systems such as NVIDIA's CUDA and Khronos consortium's open compute language (OpenCL) support a number of individual parallel application programming paradigms. To scale up the performance of some complex systems simulations, a hybrid of multi-core CPUs for coarse-grained parallelism and very many core GPUs for data parallelism is necessary. We describe our use of hybrid applica- tions using threading approaches and multi-core CPUs to control independent GPU devices. We present speed-up data and discuss multi-threading software issues for the applications level programmer and o er some suggested areas for language development and integration between coarse-grained and ne-grained multi-thread systems. We discuss results from three common simulation algorithmic areas including: partial di erential equations; graph cluster metric calculations and random number generation. We report on programming experiences and selected performance for these algorithms on: single and multiple GPUs; multi-core CPUs; a CellBE; and using OpenCL. We discuss programmer usability issues and the outlook and trends in multi-core programming for scienti c applications developers

INDIVIDUAL-BASED MODELLING OF MICROBIAL COLONY DYNAMICS ON FOOD SURFACES IN A PARALLEL SIMULATOR

International audienceThroughout the whole food processing and distribution chain, an accurate assessment and control of microbiological food safety is indispensable to avoid large outbreaks of foodborne diseases. For this reason, mathematical models are developed in predictive microbiology to describe the growth and survival of food spoiling and pathogenic microorganisms as a function of the environmental conditions during food processing and distribution. Traditionally, these models are representative for the planktonic growth of axenic microbial cultures in perfectly mixed liquid media. However, most food products are characterised by a semi-solid structure, where the contaminating cells grow out as colonies. Diffusion limitations emerge in these colonies due to the high local cell density. Hence, it is most appropriate to simulate microbial colonies at a microscopic level, considering the cell as basic modelling unit in an individual-based modelling approach. Within this respect, the MICRODIMS model has been developed at the BioTeC+ research group. However, over the last years, it became clear that the implementation of this individual-based model in the standard Repast Simphony toolkit is rather slow for the simulation of mature colonies containing a large number of cells. For this reason, MICRODIMS has been ported to the TransProg library, which uses modern general-purpose multicore and multiprocessor computers to their fullest potential. This transfer enables the simulation of mature colony dynamics in three dimensions. In this paper, the branched morphology of colonies growing on the surface of a food substrate is investigated. It is demonstrated that the emergence of this pattern is dependent on the thickness of the food substrate and structural heterogeneities at the food surface

Latency Requirements for Head-Worn Display S/EVS Applications

NASA s Aviation Safety Program, Synthetic Vision Systems Project is conducting research in advanced flight deck concepts, such as Synthetic/Enhanced Vision Systems (S/EVS), for commercial and business aircraft. An emerging thrust in this activity is the development of spatially-integrated, large field-of-regard information display systems. Head-worn or helmet-mounted display systems are being proposed as one method in which to meet this objective. System delays or latencies inherent to spatially-integrated, head-worn displays critically influence the display utility, usability, and acceptability. Research results from three different, yet similar technical areas flight control, flight simulation, and virtual reality are collectively assembled in this paper to create a global perspective of delay or latency effects in head-worn or helmet-mounted display systems. Consistent definitions and measurement techniques are proposed herein for universal application and latency requirements for Head-Worn Display S/EVS applications are drafted. Future research areas are defined

Head-tracked stereo viewing with two-handed 3D interaction for animated character construction

In this paper, we demonstrate a new interactive 3D desktop metaphor based on two-handed 3D direct manipulation registered with head-tracked stereo viewing. In our configuration, a six-degree-of-freedom head-tracker and CrystalEyes shutter glasses are used to produce stereo images that dynamically follow the user head motion. 3D virtual objects can be made to appear at a fixed location in physical space which the user may view from different angles by moving his head. The user interacts with the simulated 3D environment using both hands simultaneously. The left hand, controlling a Spaceball, is used for 3D navigation and object movement, while the right hand, holding a 3D mouse, is used to manipulate through a virtual tool metaphor, the objects appearing in front of the screen because of negative parallax. In this way, both incremental and absolute interactive input techniques are provided by the system. Hand-eye coordination is made possible by registration between virtual and physical space, allowing a variety of complex 3D tasks to be performed more easily and more rapidly than is possible using traditional interactive techniques. The system has been tested using both Polhemus Fastrak and Logitech ultrasonic input devices for tracking the head and 3D mouse.197-206Pubblicat

[[alternative]]Study and Design of a Real-Time Communication Mechanism for the Multicomputer-based High Fidelity Virtual Reality System

計畫編號：NSC89-2213-E032-017研究期間：199908~200007研究經費：568,000[[sponsorship]]行政院國家科學委員

Simulating disease transmission dynamics at a multi-scale level

We present a model of the global spread of a generic human infectious disease using a Monte Carlo micro-simulation with large-scale parallel-processing. This prototype has been constructed and tested on a model of the entire population of the British Isles. Typical results are presented. A microsimulation of this order of magnitude of population simulation has not been previously attained. Further, an efficiency assessment of processor usage indicates that extension to the global scale is feasible. We conclude that the flexible approach outlined provides the framework for a virtual laboratory capable of supporting public health policy making at a variety of spatial scales.high-performance computing; global modelling; disease transmission

Parallel simulation techniques for telecommunication network modelling

In this thesis, we consider the application of parallel simulation to the performance modelling of telecommunication networks. A largely automated approach was first explored using a parallelizing compiler to speed up the simulation of simple models of circuit-switched networks. This yielded reasonable results for relatively little effort compared with other approaches. However, more complex simulation models of packet- and cell-based telecommunication networks, requiring the use of discrete event techniques, need an alternative approach. A critical review of parallel discrete event simulation indicated that a distributed model components approach using conservative or optimistic synchronization would be worth exploring. Experiments were therefore conducted using simulation models of queuing networks and Asynchronous Transfer Mode (ATM) networks to explore the potential speed-up possible using this approach. Specifically, it is shown that these techniques can be used successfully to speed-up the execution of useful telecommunication network simulations. A detailed investigation has demonstrated that conservative synchronization performs very well for applications with good look ahead properties and sufficient message traffic density and, given such properties, will significantly outperform optimistic synchronization. Optimistic synchronization, however, gives reasonable speed-up for models with a wider range of such properties and can be optimized for speed-up and memory usage at run time. Thus, it is confirmed as being more generally applicable particularly as model development is somewhat easier than for conservative synchronization. This has to be balanced against the more difficult task of developing and debugging an optimistic synchronization kernel and the application models