Seungil Lee

LaTTe: a Java VM just-in-time compiler with fast and efficient register allocation

For network computing on desktop machines, fast execution of Java bytecode programs is essential because these machines are expected to run substantial application programs written in Java. Higher Java performance can be achieved by just-in-time (JIT) compilers which translate the stack-based bytecode into register-based machine code on demand. One crucial problem in Java JIT compilation is how to map and allocate stack entries and local variables into registers efficiently and quickly, so as to improve the Java performance. This paper introduces LaTTe, a Java JIT compiler that performs fast and efficient register mapping and allocation for RISC machines. LaTTe first translates the bytecode into pseudo RISC code with symbolic registers, which is then register allocated while coalescing those copies corresponding to pushes and pops between local variables and the stack. The LaTTe JVM also includes an enhanced object model, a lightweight monitor, a fast mark-and-sweep garbage collector, and an on-demand exception handling mechanism, all of which are closely coordinated with LaTTes JIT compilation.

Efficient Java exception handling in just-in-time compilation

The Java language provides exceptions in order to handle errors gracefully. However, the presence of exception handlers complicate the job of a JIT (Just-in-Time) compiler, including optimizations and register allocation, even though exceptions are rarely used in most programs. This paper describes some mechanisms for removing overheads imposed by the existence of exception handlers, including on-demand translation of exception handlers, which expose more optimization opportunities in normal flow. In addition, we also minimize the exception handling overhead for frequently thrown exceptions by jumping directly from the exception throwing point into the exception handler through a technique called exception handler prediction. Experiments show that the existence of exception handlers indeed does not interfere with the translation of normal flow using our exception handling mechanisms. Also, the results reveal that frequently thrown exceptions are efficiently handled with exception handler prediction.

Power system interconnection scenario and analysis between Korean peninsula and Japan

In this paper, we present possible scenarios, along with the accompanying power flow analyses and flow maps, in order to provide for the interconnection of the electric power grids between South Korea and North Korea and between South Korea and Japan. The first scenario involves the interconnection of the 765 kV HVAC power transmission system between the Kyungin area in the northwest part of South Korea and Shinpo in the eastern part of North Korea. The second scenario concerns the interconnection of the HVDC power transmission system between the Busan area in the southeast part of South Korea and the Kyushu area in the northwest part of Japan. In this paper, the various scenarios providing for the interconnection of the power systems among South Korea, North Korea and Japan are presented and the resulting interconnected power systems are simulated by means of a power flow analysis performed with the PSS/E tool.

Reducing virtual call overheads in a Java VM just-in-time compiler

Java, an object-oriented language, uses virtual methods to support the extension and reuse of classes. Unfortunately, virtual method calls affect performance and thus require an efficient implementation, especially when just-in-time (JIT) compilation is done. Inline caches and type feedback are solutions used by compilers for dynamically-typed object-oriented languages such as SELF [1, 2, 3], where virtual call overheads are much more critical to performance than in Java. With an inline cache, a virtual call that would otherwise have been translated into an indirect jump with two loads is translated into a simpler direct jump with a single compare. With type feedback combined with adaptive compilation, virtual methods can be inlined using checking code which verifies if the target method is equal to the inlined one.This paper evaluates the performance impact of these techniques in an actual Java virtual machine, which is our new open source Java VM JIT compiler called LaTTe [4]. We also discuss the engineering issues in implementing these techniques.Our experimental results with the SPECjvm98 benchhmarks indicate that while monomoprhic inline caches and polymorphic inline caches achieve a speedup as much as a geometric mean of 3% and 9% respectively, type feedback cannot improve further over polymorphic inline caches and even degrades the performance for some programs.

Assessing the spatial equity of Seoul’s public transportation using the Gini coefficient based on its accessibility

ABSTRACT The purpose of this research is to develop a methodology for calculating the index of the spatial equity for the public transportation services for the city of Seoul using the Lorenz curve and Gini coefficient based on accessibility to the services. The index was estimated for 100 m × 100 m cells first and then aggregated for 424 traffic analysis zones (TAZs) in the city. The indices for Seoul’s subway and bus were represented with and without the weighting factor. On the basis of this methodology, this study assessed the effect of an additional subway line on the spatial equity before and after its operation. Furthermore, an index of relative difference indicating the change in population and employment in the station areas was applied to investigate the changed effects of spatial equity between population and employment from the new subway line. The core findings from this research are summarized as follows. First, the subway network of Seoul provides more unequal public transportation services for the TAZs than for the bus network. Second, an improvement in the operation frequency of both transit modes would deepen the spatial inequity of Seoul. Third, a subway extension plan for Seoul could noticeably reduce the spatial inequity. The plan would improve the spatial equity for the population more than that for employment. The most important meaning of this study is to be found in combining spatial equity on the supply side with transit-oriented development (TOD) on the demand side. So, by establishing a TOD policy for the additional subway station areas, an appropriate land-use pattern can be established for maximizing potential ridership in consideration of the combination.

An appraisal of the urban scheme for sustainable urban transport

The purpose of this study is to appraise the impact of integrated land use and transport policies on environmental objectives for sustainable urban transport. Furthermore, while considering environmental objectives, we find the most effective policy from an existing policy case and policy scenarios for Namyangju-City, in the Seoul Metropolitan Area, as an experimental appraisal. The simulation results show that the CO2 emissions reduction effects of the policy scenarios of integrated land use and transport is greater than those of existing policies. Specifically, the large-scale development plan, such as scenario 2, which is the development scenario of the subcenter-area in Namyangju-City, is more effective than scenarios 1 and 3. While the effect of scenario 2 is evenly spread across the city, the effect of scenario 1 is noticeable in the central-area and the local district-area, and the total reduction of CO2 emissions within scenario 2 of the subcenter-area is similar to the central-area development of scenario 1. The CO2 emissions reduction effect of Scenario 3, which is the development of the local district-area in Namyangju-City, is relatively lower than that of any other scenarios. Also, it is effective all over Namyangju-City but ineffective for the local district-area. Comparing the CO2 emissions per capita, while a do-nothing case is estimated to emit 1.95 tonnes of CO2 in 2031, the results of an existing policy case and policy scenarios 1, 2, 3 are estimated to fall to 1.50 tonnes in 2031 from 1.72∼1.79 tonnes in 2016.

A study on the impact of soft location factors in the relocation of service and manufacturing firms

This paper empirically studied relocation factors for manufacturing and service firms in the Seoul Metropolitan Area. The purpose of this study is to identify the influence not only of traditional firm location factors, but also of quality of life factors. A firms location decision is an assertive action (behaviour) to maximize profit that may have a large ripple effect on the regional economy and society. This study used a binary logit model to analyse location choice factors during firm relocations. As of December 2011, the number of firms registered with the Korea Chamber of Commerce and Industry was 117,157. Of these firms, 36,598 were selected. The firms’ locations could be tracked because their names and owners did not change from December 2006 to December 2012. Of the selected firms, 8328 (22.8%) relocated during this period. It can be considered that 4.6% of all firms relocate in a year. A geographic information system database was built using location addresses of the 8328 firms. This study exhibited a trend that manufacturing firms moved from cities to suburbs, where transport and industry conditions were more favourable. By contrast, firms in higher-order industries with high-added value moved to city centres, where living conditions were more favourable. This trend suggests that quality of life factors have become more important in firm location decisions. This study is expected to be used to understand changes in firm locations and relocations, and to help make industrial policies for drawing firms.

Reviewing Korea's Strategic Plan of Adaptation and Mitigation for Sustainable Development and Climate Change

This article introduces Koreas Five Year Green Growth Plan (FYGGP) as the national policy portfolio framework, assesses the weakness of FYGGP using the Adaptation Policy Framework (APF)s principals, and proposes three ideas to improve FYGGP. The first idea is setting up the Total Management System for Climate Changes (TMSCC) that consists of an effective integration process with existing authorities and plans; strong institutional support; monitoring and evaluation processes; and responsive adjusting mechanisms. The second idea is effectively applying the inventory of TMSCC to decide and modify the national policy. The TMSCC needs an independent agent under the Korean Presidential Committee which can coordinate and manage it, so that sustainability indicators and standards of judgment for mitigation can be developed and announced. The final idea is taking a systematic evaluation that can upgrade the TMSCC, linked with policy directions, as a suitability evaluation about TMSCC itself needs a process making the system; an efficiency evaluation needs a process modifying the system and a process applying policy scenarios; an accuracy evaluation needs a process forecasting policy effects and climate change impacts. This evaluation cycle can help achieve the national objectives.

Evaluating integrated land use and transport strategies in the urban regeneration projects toward sustainable urban structure: case studies of Hafen City in Germany and Shinagawa Station in Tokyo

Due to the emergence of urban regeneration, there have been many case studies on urban regeneration projects. However, there has been little research on a successful project that may be helpful for the execution of a sustainable urban structure policy. This study analyses the strategies and characteristics of two successful representative urban regeneration projects that aimed toward a sustainable urban structure, from the viewpoint of land-use transport interaction. For this purpose, we conducted a literature review on the theory of sustainable urban structures and land-use transport interaction and analysed the major strategies and planning characteristics of HafenCity and Shinagawa Station area. In this study, we found that two cases considered an integrated approach of land use and transport to achieve sustainable urban structures that also emphasized regional characteristics and planning factors based on the goal of the projects. As a result, we concluded that a sustainable urban regeneration project should be based on integrated consideration in local context, transport systems and regional characteristics.

Application of the Urban Green Assessment Model for the Korean Newtowns

In this study the Korean newtowns were appraised in terms of green use by dwellers using the assessment model of urban greens developed on the basis of accessibility to green space. The model was assumed through a survey on the dwellers of the two developed newtowns, which represent basically different spatial structures: Pyeongchon with a latticed urban form and Sanbon with a clustered one. The assumed model was applied to a newtown developed in 90s (Sanbon) and a newtown in process (Dongtan) in order to verify an improvement between the two newtowns with respect to the use of greens. According to the model application the green rate weighted by potential users increased by 7.56% points for Dongtan and 4.11% points for Sanbon. However, the increasing ratio of Sanbons one (25.90%) is greater than that of Dongtans one (23.42%). This confirms that the use of greens could be determined more influentially by their spatial form and arrangement than by their area. For this analysis a Binary Logit Model, SPSS 12.0, ArcGIS were used.