Ruei Chuan Chang

EJVM: an economic Java run-time environment for embedded devices

As network‐enabled embedded devices and Java grow in their popularity, embedded system researchers start seeking ways to make these devices Java‐enabled. However, it is a challenge to apply Java technology to these devices due to their shortage of resources.

Resource sharing digital libraries: a case study of Taiwan's InfoSpring Digital Library Project

The InfoSpring Digital Library Project conducted by National Chiao Tung University (NCTU) is a project to establish mirror sites in Taiwan for well-known reference databases and full-text electronic journals. The role of NCTU in this project is to provide the hardware (including servers and storage space) and network infrastructure, system maintenance and data update. By means of resource sharing, universities and industries in Taiwan can access the databases loaded in the InfoSpring Digital Library under certain subscription agreements. Realizing the importance of resource sharing, libraries in Taiwan have organized a consortium to decide which databases to be hosted in Taiwan and negotiate competitive prices with information providers. This paper presents the motivation, current status, experiences, and future directions of the InfoSpring Project and introduces the Taiwanese library consortium which it services.

Ray-cast volume rendering accelerated by incremental trilinear interpolation and cell templates

Two related ideas for improving the speed of ray-cast volume rendering are studied in this paper. The first is an incremental algorithm for trilinear interpolation, a method commonly used in ray-cast volume rendering to calculate sample values. The incremental algorithm can expedite trilinear interpolation when many samples along a ray are located in one cell. The second is an efficient hybrid volume rendering restricted to parallel projection. In the preprocessing stage, acell template is created to store the information used by the incremental trilinear interpolation. When a cell is parallel projected, the information is retrieved from the template to compute the cell contribution. Because the algorithm with only one template may cause aliasing, an antialiasing technique exploiting multiple cell templates is proposed. With our method, ray-cast volume rendering can be accelerated considerably.

Adaptive-level memory caches on world wide web servers

Abstract Owing to the fast growth of World Wide Web (WWW), web traffic has become a major component of Internet traffics. Consequently, the reduction of document retrieval latency on WWW becomes more and more important. The latency can be reduced in two ways: reduction of network delay and improvement of web servers’ throughput. Our research aims at improving a web server’s throughput by keeping a memory cache in a web server’s address space. In this paper, we focus on the design and implementation of a memory cache scheme. We propose a novel web cache management policy named the adaptive-level policy that either caches the whole file content or only a portion of it, according to the file size. The experimental results show three things. First, our memory cache is beneficial since, under our experimental workloads, the throughput improvement can achieve 32.7%. Second, our cache management policy is suitable for current web traffic. Third, with the increasing popularity of multimedia files, our policy will outperform others currently used in WWW.

Sample buffer: A progressive refinement ray-casting algorithm for volume rendering

Abstract Ray-casting has been shown to be an excellent technique for rendering volume data. This paper describes a new ray-casting algorithm that employs the concept of progressive refinement for volume rendering. Volume data are embedded into a complete octree, and when the volume data are rendered, the octree is traversed according to a user-defined threshold. By reducing this threshold gradually, we can render increasingly refined images. Ray-casting is used to explore the octree, and a data structure called a sample buffer (SB) is introduced to reduce the time required to render a series of images. With this method, a satisfactory balance between image quality and computation time can be achieved.

OS portal: an economic approach for making an embedded kernel extensible

With the rapid development of embedded system techniques and Internet technologies, network-enabled embedded devices have grown in their popularity. One critical design trend of such devices is that they are shifting from static and fixed-function systems to more dynamic and extensible ones, which are capable of running various kinds of applications. To support the diversity of the applications, kernels on these devices must be extensible. However, making embedded kernels extensible is challenging due to the shortage of resources on these devices.In this paper, we propose the operating system portal framework, which makes embedded kernels become extensible while keeping the added overheads minimal. By storing kernel modules on a resource-rich server and loading them on demand, the need for equipping a local storage on the device is eliminated. In addition, we propose mechanisms for reducing the memory requirements and performing on-line module replacement on the embedded devices.According to the performance evaluation, our approach requires only 1% of the resource requirements, compared to the traditional approaches. This allows our framework to be applied on a wide range of embedded devices.

An efficient hierarchical-traversal algorithm for ray tracing

Ray tracing has been shown to be an excellent technique for rendering realistic images. However, it is important to reduce the lengthy computation time resulting from the brute-force nature of the original ray-tracing algorithms. In this paper, two ideas are proposed to speep up the well-known hierarchical subdivision method. First, a new hierarchy traversal scheme is described to reduce the number of raybounding volume intersection tests for secondary rays. Then, a plane-sweep method is proposed to make fewer intersection checks for eye rays. Experiments and discussions are presented to prove the feasibility of our methods.

nDriver: Online Driver Replacement for Increasing Operating System Availability

Device drivers are the most unreliable part of an operating system. In this paper, we propose a framework called nDriver. Based on the design diversity concept, it uses multiple implementations of a device driver to survive from driver faults. Once a fault happens in a driver, nDriver can dynamically replace the faulty driver with another implementation, instead of allowing the faulty driver to crash the system. The unique features of nDriver are as follows. First, it can detect two major kinds of driver faults, the exception and blocking faults. Second, the requests issued to the driver will not be lost due to the driver replacement. Third, the driver replacement is transparent to all the other kernel subsystems. Fourth, nDriver requires no modification to the existing operating system or driver codes. The major contribution of this work is that nDriver implements the concept of design diversity at the device driver layer. Moreover, it achieves the goal of seamless driver replacement and improves operating system availability without modifying the existing operating system or driver codes. We implemented nDriver as a kernel module in Linux. Currently, it can recover the system from faults in network device drivers. However, the mechanisms can be adapted to other module-based device drivers with a slight extension. According to the performance evaluation, the overhead of nDriver is no more than 3.5% and the recovery time is quite small. This indicates that nDriver is an efficient mechanism to increase the availability of an operating system.

HANet: a framework toward ultimately reliable network services

High availability is becoming an essential part of network services because even a little downtime may lead to a great loss of money. According to previous research, network failure is one of the major causes of system unavailability. In this paper, we propose a framework called HANet for building highly available network services. The main goal of HANet is to allow a server to continue providing services when all its network interfaces to the outside world (i.e., public interfaces) have failed. This is achieved by two techniques. First, a network interface can be backed up not only by other public network interfaces, but also by other inter-server I/O communication interfaces (i.e., private interfaces) such as Ethernet, USB, RS232, etc. Therefore, IP packets can still be transmitted and received via these I/O links, even when all of the public network interfaces have failed. Second, HANet allows a server to take over the packet transmission job of another network-failed server. The benefit of HANet is that a network-failed server will not lose any requests which are being processed. And, it is efficient since no synchronization overhead or replaying process is required. Moreover, it is totally transparent to server applications and clients. To demonstrate the feasibility of HANet, we implemented it in the Linux kernel. According to the performance results, using a private Fast Ethernet interface for data communication leads to only 1% overhead in user-perceived latency when the public Fast Ethernet interface of the server has failed. This indicates that HANet is efficient, and hence is feasible for commercial network services.

RPC‐News: a real‐time, personalized, Chinese news system

With the speedy growth of information quantity, people need a mechanism to discover automatically the information that interests them. Such a mechanism is called selective dissemination of information (SDI). Describes the design and implementation of an SDI system with the ability of delivering real‐time, personalized news articles. In addition to delivering English news, it delivers Chinese articles also. Focuses on the problems that other researches seldom address. First, discusses how to store and delete news articles efficiently, then describes the user model to let users specify their interests. Finally, presents an efficient method to embed the ability to deliver Chinese as well as English news articles in the system.