Concurrency and Computation:Practice and Experience

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Articles under Consideration for Journal

• C467: VGDS: A Distributed Data Structure Framework for Scientific Computation
  • Abstract: This paper gives an overview of the VGDS (Virtual Global Data Structure) project. The VGDS effort focuses on developing an integrated, distributed environment that allows fast prototyping of a diverse set of simulation problems in irregular scientific and engineering domains, focusing on computations with irregular and adaptive structures. The framework defines two base libraries: unstructured mesh and adaptive tree, that capture major data structures involved inirregular scientic computation. The framework defines multiple layers of class libraries which work together to provide data-parallel representations to application developers while encapsulate parallel implementation details into lower layers of the framework. The layered approach enables easy extension of the base libraries to a variety of application-specific data structures. Experimental results on a network of workstations is reported.
  • Pangfeng Liu, Jan-Jan Wu
  • mailto:wuj@iis.sinica.edu.twmailto:pangfeng@cs.ccu.edu.tw
  • Submitted April 21, 2000
• C468: cJVM: A Cluster JVM Architecture for Single System Image
  • Abstract:cJVM is a Java Virtual Machine (JVM) which provides a single system image of a traditional JVM while executing in a distributed fashion on the nodes of a cluster. cJVM virtualizes the cluster, supporting any pure Java application without requiring that applications be tailored specifically for it. The aim of cJVM is to obtain improved scalability for a class of Java Server Applications by distributing the application's work among the cluster's computing resources. cJVM is based on a novel object model which distinguishes between an application's view of an object (e.g., every object is a unique data structure) and its implementation (e.g., objects may have consistent replications on different nodes). This enables us to exploit knowledge on the usage of individual objects to improve performance (e.g., using object replications to increase locality of access to objects). Currently, we have already completed a prototype which runs pure Java applications on a cluster of NT workstations connected via a Myrinet fast switch. The prototype provides a single system image to applications, distributing the application's threads and objects over the cluster. We have used cJVM to run without change a real Java Server Application containing over 10K loc and achieve high scalability for it on a cluster. We also achieved linear speedup for another application with a large number of independent threads. This paper discusses cJVM's architecture and implementation. It focuses on achieving a single system image for a traditional JVM on a cluster while describing in short how we aim at obtaining scalability.
  • Yariv Aridor, Michael Factor and Avi Teperman
  • mailto:teperman@il.ibm.com
  • Submitted May 1, 2000
• C474: Parallel solution of rotating flows in cavities
  • Abstract:In this paper, we investigate the parallel solution to the rotating internal flow problems, using the Navier-Stokes equations as proposed in [16] and [15]. A Runge-Kutta time-stepping scheme was applied to the equations and both sequential and message- passing implementations were developed, the latter using MPI , and were tested on an SGI Origin200 distributed, global shared memory parallel computer. The results show that our approach to parallelize the sequential implementation requires little effort whilst providing good results even for medium-sized problems, on this particular computer.
  • Rudnei Dias da Cunha and Alvaro Luiz de Bortoli
  • mailto:rudnei@mat.ufrgs.br
  • Submitted May 14, 2000
  • Electronic version:C474dacunha/rotflow.pdf
  • Submit Info:C474dacunha
• C475: Analysis and Measurement of the Eect of Kernel Locks in SMP Systems
  • Abstract:This paper reports the use of case studies to evaluate the performance degradation caused by the kernel-level lock. We define the lock ratio as a ratio of the execution time for critical sections to the total execution time of a parallel program. The kernel-level lock ratio determines how effective programs work on Symmetric MultiProcessor systems. We have measured the lock ratios and the performance of three types of parallel programs on SMP systems with Linux 2.0: matrix multiplication, parallel make, and WWW server programs. Experimental results show that the higher the lock ratio of parallel programs, the worse their performance becomes. keywords: SMP Systems, Operating Systems, Parallel Programs, Per- formance Evaluation, Kernel Lock
  • Akihiro Kaieda and Yasuichi Nakayama; Atsuhiro Tanaka, Takashi Horikawa, Toshiyasu Kurasugi and Issei Kino
  • mailto:yasu@cs.uec.ac.jp
  • Submitted May 24, 2000