Evaluation and optimization of method calls in Java

Recent advances in Virtual Machine's technology have led to the diffusion of Java execution environments which provide performance levels comparable to those of traditional languages such as C/C++ and Fortran. This paper's focus is on method calls, a well researched area of compilers' optimization. In particular, we evaluate the impact on the performance of the Java virtual call mechanism and the advantages which can be obtained through the inlining optimization. Moreover, we propose a new heuristic methodology which allows us to consider whole sequences of methods for the inlining decision and not only simple couples of caller–callee methods. The proposed methodology operates at bytecode level and is applicable only to the calls that can be resolved at compile time. Thus, we execute a devirtualization algorithm before the inlining decision, in order to enlarge the basis for the optimization. We made empirical measures on three major platforms (Unix, Windows and Linux) by using the SPEC JVM98 benchmark suite. Results reveal an average performance improvement of 1.9% with devirtualization and 5.5% with inlining. We discuss the different behaviour of single benchmarks and virtual machines, arguing that dynamic compilers are not yet able to fully exploit the wider scope for intra‐procedural optimization offered by eliminating the calls. Finally, we show that taking into consideration whole sequences of calls—instead of single calls—is effective only on a few benchmarks where hotspots of execution involve cycles of nested methods. Copyright © 2003 John Wiley & Sons, Ltd.     

Luminescent dichroic‐dye‐doped cholesteric liquid‐crystal displays

Abstract— LCDs based on a luminescent dichroic‐dye‐doped non‐absorbing cholesteric LC with positive dielectric anisotropy is proposed. In the initial state, the orientation of the dye molecules provides effective light absorption and irradiation. By applying an electric field to the cell, the absorption and thus the luminescence is absent. A two‐color luminescence could be achieved by sandwiching two cells: the upper cell consists of a cholesteric LC with two dyes (sensitizer and emitter) and is used with an applied voltage (active cell); the lower cell consists of a cholesteric LC doped with one dye and works without applying a voltage (passive cell). The performance characteristics of luminescent dye‐doped cholesteric‐LCDs were investigated.     

Minimum makespan task sequencing with multiple shared resources

In this paper we study the general problem of sequencing multiple jobs, where each job consists of multiple ordered tasks and tasks execution requires simultaneous usage of several resources. In particular, the case of an automatic assembly cell is examined. NP-completeness results are given. A heuristic is designed and evaluated.     

A conservative and monotone mixed-hybridized finite element approximation of transport problems in heterogeneous domains

In this article, we discuss the numerical approximation of transport phenomena occurring at material interfaces between physical subdomains with heterogenous properties. The model in each subdomain consists of a partial differential equation with diffusive, convective and reactive terms, the coupling between each subdomain being realized through an interface transmission condition of Robin type. The numerical approximation of the problem in the two-dimensional case is carried out through a dual mixed-hybridized finite element method with numerical quadrature of the mass flux matrix. The resulting method is a conservative finite volume scheme over triangular grids, for which a discrete maximum principle is proved under the assumption that the mesh is of Delaunay type in the interior of the domain and of weakly acute type along the domain external boundary and internal interface. The stability, accuracy and robustness of the proposed method are validated on several numerical examples motivated by applications in biology, electrophysiology and neuroelectronics.     

An incremental clustering scheme for data de-duplication

We propose an incremental technique for discovering duplicates in large databases of textual sequences, i.e., syntactically different tuples, that refer to the same real-world entity. The problem is approached from a clustering perspective: given a set of tuples, the objective is to partition them into groups of duplicate tuples. Each newly arrived tuple is assigned to an appropriate cluster via nearest-neighbor classification. This is achieved by means of a suitable hash-based index, that maps any tuple to a set of indexing keys and assigns tuples with high syntactic similarity to the same buckets. Hence, the neighbors of a query tuple can be efficiently identified by simply retrieving those tuples that appear in the same buckets associated to the query tuple itself, without completely scanning the original database. Two alternative schemes for computing indexing keys are discussed and compared. An extensive experimental evaluation on both synthetic and real data shows the effectiveness of our approach.     

Analytical study of intradomain handover in multiple-mobile-routers-based multihomed NEMO networks

The need to stay connected to the Internet “anytime” and “anywhere” is becoming more and more required in the recent years with the development of wireless networks. The NEMO basic support protocol was developed to grant the Internet connection for an entire mobile network, like vehicle or aircraft network. In NEMO a Mobile Router manages the mobility of the entire network on behalf of the other nodes in order to reduce the overhead of signaling messages. The critical part of mobility support is to reduce the handover latency, particularly when a Mobile Router is not reachable. This handover period degrades the performance of most delay sensitive applications. Referring to our proposition for NEMO handover improvement which is conceived for multiple-mobile-routers-based multihomed NEMO network, we find out a mathematical model to study the intradomain handover performance. We derive the mathematical model to analyze interruption interval (the time interval during which none of mobile routers can transport packets) during the intradomain handover. We study the impact of varying critical parameters, like vehicle speed, overlapping coverage distance, distance between mobile routers, and scanning frequency. The obtained results reveal that the seamless handover can be achieved if network configuration parameters are correctly chosen.     

Validating scheduling approaches against executional uncertainty

This paper introduces a general methodology to perform a comparative evaluation of different approaches to the problem of scheduling with uncertainty. Different proactive (off-line) and reactive (on-line) scheduling policies are evaluated by simulating the execution of a number of baseline schedules under uncertain environmental conditions, and observing the solution behaviors as such schedules get stressed by exogenous events. The analysis aims at assessing the impact of both proactive and reactive scheduling efforts on the robustness of the baseline solutions, against measurable disrupting factors, through reproducible experiments. As the results show, this dynamic approach reveals extremely useful to unveil some subtle aspects, which would have remained undetected through static metric evaluations.