A taxonomy of application scheduling tools for high performance cluster computing

Application scheduling plays an important role in high-performance cluster computing. Application scheduling can be classified as job scheduling and task scheduling. This paper presents a survey on the software tools for the graph-based scheduling on cluster systems with the focus on task scheduling. The tasks of a parallel or distributed application can be properly scheduled onto multi-processors in order to optimize the performance of the program (e.g., execution time or resource utilization). In general, scheduling algorithms are designed based on the notion of task graph that represents the relationship of parallel tasks. The scheduling algorithms map the nodes of a graph to the processors in order to minimize overall execution time. Although many scheduling algorithms have been proposed in the literature, surprisingly not many practical tools can be found in practical use. After discussing the fundamental scheduling techniques, we propose a framework and taxonomy for the scheduling tools on clusters. Using this framework, the features of existing scheduling tools are analyzed and compared. We also discuss the important issues in improving the usability of the scheduling tools. This work is supported by the Hong Kong Polytechnic University under grant H-ZJ80 and by NASA Ames Research Center by a cooperative grant agreement with the University of Texas at Arlington. Jiannong Cao received the BSc degree in computer science from Nanjing University, Nanjing, China in 1982, and the MSc and the Ph.D degrees in computer science from Washington State University, Pullman, WA, USA, in 1986 and 1990 respectively. He is currently an associate professor in Department of Computing at the Hong Kong Polytechnic University, Hong Kong. He is also the director of the Internet and Mobile Computing Lab in the department. He was on the faculty of computer science at James Cook University and University of Adelaide in Australia, and City University of Hong Kong. His research interests include parallel and distributed computing, networking, mobile computing, fault tolerance, and distributed software architecture and tools. He has published over 120 technical papers in the above areas. He has served as a member of editorial boards of several international journals, a reviewer for international journals/conference proceedings, and also as an organizing/programme committee member for many international conferences. Dr. Cao is a member of the IEEE Computer Society, the IEEE Communication Society, IEEE, and ACM. He is also a member of the IEEE Technical Committee on Distributed Processing, IEEE Technical Committee on Parallel Processing, IEEE Technical Committee on Fault Tolerant Computing, and Computer Architecture Professional Committee of the China Computer Federation. Alvin Chan is currently an assistant professor at the Hong Kong Polytechnic University. He graduated from the University of New South Wales with a Ph.D. degree in 1995 and was subsequently employed as a Research Scientist by the CSIRO, Australia. From 1997 to 1998, he was employed by the Centre for Wireless Communications, National University of Singapore as a Program Manager. Dr. Chan is one of the founding members and director of a university spin-off company, Information Access Technology Limited. He is an active consultant and has been providing consultancy services to both local and overseas companies. His research interests include mobile computing, context-aware computing and smart card applications. Yudong Sun received the B.S. and M.S. degrees from Shanghai Jiao Tong University, China. He received Ph.D. degree from the University of Hong Kong in 2002, all in computer science. From 1988 to 1996, he was among the teaching staff in Department of Computer Science and Engineering at Shanghai Jiao Tong University. From 2002 to 2003, he held a research position at the Hong Kong Polytechnic University. At present, he is a Research Associate in School of Computing Science at University of Newcastle upon Tyne, UK. His research interests include parallel and distributed computing, Web services, Grid computing, and bioinformatics. Sajal K. Das is currently a Professor of Computer Science and Engineering and the Founding Director of the Center for Research in Wireless Mobility and Networking (CReWMaN) at the University of Texas at Arlington. His current research interests include resource and mobility management in wireless networks, mobile and pervasive computing, sensor networks, mobile internet, parallel processing, and grid computing. He has published over 250 research papers, and holds four US patents in wireless mobile networks. He received the Best Paper Awards in ACM MobiCom’99, ICOIN-16, ACM, MSWiM’00 and ACM/IEEE PADS’97. Dr. Das serves on the Editorial Boards of IEEE Transactions on Mobile Computing, ACM/Kluwer Wireless Networks, Parallel Processing Letters, Journal of Parallel Algorithms and Applications. He served as General Chair of IEEE PerCom’04, IWDC’04, MASCOTS’02 ACM WoWMoM’00-02; General Vice Chair of IEEE PerCom’03, ACM MobiCom’00 and IEEE HiPC’00-01; Program Chair of IWDC’02, WoWMoM’98-99; TPC Vice Chair of ICPADS’02; and as TPC member of numerous IEEE and ACM conferences. Minyi Guo received his Ph.D. degree in information science from University of Tsukuba, Japan in 1998. From 1998 to 2000, Dr. Guo had been a research scientist of NEC Soft, Ltd. Japan. He is currently a professor at the Department of Computer Software, The University of Aizu, Japan. From 2001 to 2003, he was a visiting professor of Georgia State University, USA, Hong Kong Polytechnic University, Hong Kong. Dr. Guo has served as general chair, program committee or organizing committee chair for many international conferences, and delivered more than 20 invited talks in USA, Australia, China, and Japan. He is the editor-in-chief of the Journal of Embedded Systems. He is also in editorial board of International Journal of High Performance Computing and Networking, Journal of Embedded Computing, Journal of Parallel and Distributed Scientific and Engineering Computing, and International Journal of Computer and Applications. Dr. Guo’s research interests include parallel and distributed processing, parallelizing compilers, data parallel languages, data mining, molecular computing and software engineering. He is a member of the ACM, IEEE, IEEE Computer Society, and IEICE. He is listed in Marquis Who’s Who in Science and Engineering.     

An Autonomic Reservoir Framework for the Stochastic Optimization of Well Placement

The adequate location of wells in oil and environmental applications has a significant economic impact on reservoir management. However, the determination of optimal well locations is both challenging and computationally expensive. The overall goal of this research is to use the emerging Grid infrastructure to realize an autonomic self-optimizing reservoir framework. In this paper, we present a policy-driven peer-to-peer Grid middleware substrate to enable the use of the Simultaneous Perturbation Stochastic Approximation (SPSA) optimization algorithm, coupled with the Integrated Parallel Accurate Reservoir Simulator (IPARS) and an economic model to find the optimal solution for the well placement problem. Wolfgang Bangerth is a postdoctoral research fellow at both the Institute for Computational Engineering and Sciences, and the Institute for Geophyics, at the University of Texas at Austin. He obtained his Ph.D. in applied mathematics from the University of Heidelberg, Germany in 2002. He is the project leader for the deal.II finite element library (http://www.dealii.org). Wolfgang is a member of SIAM, AAAS, and ACM. Hector Klie obtained his Ph.D. degree in Computational Science and Engineering at Rice University, 1996, he completed his Master and undergraduate degrees in Computer Science at the Simon Bolivar University, Venezuela in 1991 and 1989, respectively. Hector Klie's main research interests are in the development of efficient parallel linear and nonlinear solvers and optimization algorithms for large-scale transport and flow of porous media problems. He currently holds the position of Associate Director and Senior Research Associate in the Center for Subsurface Modeling at the Institute of Computational Science and Engineering at The University of Texas at Austin. Dr. Klie is current member of SIAM, SPE and SEG. Vincent Matossian obtained a Masters in applied physics from the French Université Pierre et Marie Curie. Vincent is currently pursuing a Ph.D. degree in distributed systems at the Department of Electrical and Computer Engineering at Rutgers University under the guidance of Manish Parashar. His research interests include information discovery and ad-hoc communication paradigms in decentralized systems. Manish Parashar is Professor of Electrical and Computer Engineering at Rutgers University, where he also is director of the Applied Software Systems Laboratory. He received a BE degree in Electronics and Telecommunications from Bombay University, India and MS and Ph.D. degrees in Computer Engineering from Syracuse University. He has received the Rutgers Board of Trustees Award for Excellence in Research (2004–2005), NSF CAREER Award (1999) and the Enrico Fermi Scholarship from Argonne National Laboratory (1996). His research interests include autonomic computing, parallel & distributed computing (including peer-to-peer and Grid computing), scientific computing, software engineering. He is a senior member of IEEE, a member of the IEEE Computer Society Distinguished Visitor Program (2004–2007), and a member of ACM. Mary Fanett Wheeler obtained her Ph.D. at Rice University in 1971. Her primary research interest is in the numerical solutions of partial differential systems with applications to flow in porous media, geomechanics, surface flow, and parallel computation. Her numerical work includes formulation, analysis and implementation of finite-difference/finite-element discretization schemes for nonlinear, coupled PDE's as well as domain decomposition iterative solution methods. She has directed the Center for Subsurface Modeling, The University of Texas at Austin, since its creation in 1990. Dr. Wheeler is recepient of the Ernest and Virginia Cockrell Chair in Engineering and is Professor in the Department of Aerospace Engineering & Engineering Mechanics and in the Department of Petroleum & Geosystems Engineering of The University of Texas     

Deferred Assignment Scheduling in Cluster-Based Servers

This paper proposes a new scheduling policy for cluster-based servers called DAS (Deferred Assignment Scheduling). The main idea in DAS is to defer scheduling as much as possible in order to make better use of the accumulated information on job sizes. In broad outline, DAS operates as follows: (1) incoming jobs are held by the dispatcher in a buffer; (2) the dispatcher monitors the number of jobs being processed by each server; (3) when the number of jobs at a server queue drops below a prescribed threshold, the dispatcher sends to it the shortest job in its buffer. To gauge the efficacy of DAS, the paper presents simulation studies, using various data traces. The studies collected response times and slowdowns for two cluster configurations under multi-threaded and multi-process back-end server architectures. The experimental results show that in both architectures, DAS outperforms the Round-Robin policy in all traffic regimes, and the JSQ (Join Shortest Queue) policy in medium and heavy traffic regimes. Victoria Ungureanu (ACM) is a visiting researcher at DIMACS. She has a Ph.D. in Computer Science from Rutgers University. Benjamin Melamed is a Professor II at the Rutgers Business School- Newark and New Brunswick, Department of MSIS. Melamed received a B.Sc. degree in Mathematics and Statistics from Tel Aviv University in 1972, and a M.S. and Ph.D. degrees in Computer Science from the University of Michigan in 1973 and 1976, respectively. He was awarded an AT&T Fellow in 1988 and an IEEE Fellow in 1994. He became an IFIP WG7.3 member in 1997, and was elected to Beta Gamma Sigma in 1998. Michael N. Katehakis is Professor of Management Science in the Department of Management Science and Information Systems, at Rutgers. He studied at the University of Athens, Diploma (1974) in Mathematics, at the University of South Florida, M.A. (1978) in Statistics, and at Columbia University, Ph.D. (1980) in Operations Research. He won the 1992 Wolfowitz Prize (with Govindarajulu Z.) Phillip G. Bradford (ACM) is on the faculty in Computer Science Department at the University of Alabama. He earned his Ph.D. at Indiana University in Bloomington, his MS at The University of Kansas and his BS at Rutgers University.     

A flexible multi-dimensional QoS performance measure framework for distributed heterogeneous systems

When users’ tasks in a distributed heterogeneous computing environment (e.g., cluster of heterogeneous computers) are allocated resources, the total demand placed on some system resources by the tasks, for a given interval of time, may exceed the availability of those resources. In such a case, some tasks may receive degraded service or be dropped from the system. One part of a measure to quantify the success of a resource management system (RMS) in such a distributed environment is the collective value of the tasks completed during an interval of time, as perceived by the user, application, or policy maker. The Flexible Integrated System Capability (FISC) measure presented here is a measure for quantifying this collective value. The FISC measure is a flexible multi-dimensional measure such that any task attribute can be inserted and may include priorities, versions of a task or data, deadlines, situational mode, security, application- and domain-specific QoS, and task dependencies. For an environment where it is important to investigate how well data communication requests are satisfied, the data communication request satisfied can be the basis of the FISC measure instead of tasks completed. The motivation behind the FISC measure is to determine the performance of resource management schemes if tasks have multiple attributes that needs to be satisfied. The goal of this measure is to compare the results of different resource management heuristics that are trying to achieve the same performance objective but with different approaches. This research was supported by the DARPA/ITO Quorum Program, by the DARPA/ISO BADD Program and the Office of Naval Research under ONR grant number N00014-97-1-0804, by the DARPA/ITO AICE program under contract numbers DABT63-99-C-0010 and DABT63-99-C-0012, and by the Colorado State University George T. Abell Endowment. Intel and Microsoft donated some of the equipment used in this research. Jong-Kook Kim is pursuing a Ph.D. degree from the School of Electrical and Computer Engineering at Purdue University (expected in August 2004). Jong-Kook received his M.S. degree in electrical and computer engineering from Purdue University in May 2000. He received his B.S. degree in electronic engineering from Korea University, Seoul, Korea in 1998. He has presented his work at several international conferences and has been a reviewer for numerous conferences and journals. His research interests include heterogeneous distributed computing, computer architecture, performance measure, resource management, evolutionary heuristics, and power-aware computing. He is a student member of the IEEE, IEEE Computer Society, and ACM. Debra Hensgen is a member of the Research and Evaluation Team at OpenTV in Mountain View, California. OpenTV produces middleware for set-top boxes in support of interactive television. She received her Ph.D. in the area of Distributed Operating Systems from the University of Kentucky. Prior to moving to private industry, as an Associate Professor in the systems area, she worked with students and colleagues to design and develop tools and systems for resource management, network re-routing algorithms and systems that preserve quality of service guarantees, and visualization tools for performance debugging of parallel and distributed systems. She has published numerous papers concerning her contributions to the Concurra toolkit for automatically generating safe, efficient concurrent code, the Graze parallel processing performance debugger, the SAAM path information base, and the SmartNet and MSHN Resource Management Systems. Taylor Kidd is currently a Software Architect for Vidiom Systems in Portland Oregon. His current work involves the writing of multi-company industrial specifications and the architecting of software systems for the digital cable television industry. He has been involved in the establishment of international specifications for digital interactive television in both Europe and in the US. Prior to his current position, Dr. Kidd has been a researcher for the US Navy as well as an Associate Professor at the Naval Postgraduate School. Dr Kidd received his Ph.D. in Electrical Engineering in 1991 from the University of California, San Diego. H. J. Siegel was appointed the George T. Abell Endowed Chair Distinguished Professor of Electrical and Computer Engineering at Colorado State University (CSU) in August 2001, where he is also a Professor of Computer Science. In December 2002, he became the first Director of the CSU Information Science and Technology Center (ISTeC). ISTeC is a university-wide organization for promoting, facilitating, and enhancing CSU’s research, education, and outreach activities pertaining to the design and innovative application of computer, communication, and information systems. From 1976 to 2001, he was a professor at Purdue University. He received two BS degrees from MIT, and the MA, MSE, and PhD degrees from Princeton University. His research interests include parallel and distributed computing, heterogeneous computing, robust computing systems, parallel algorithms, parallel machine interconnection networks, and reconfigurable parallel computer systems. He has co-authored over 300 published papers on parallel and distributed computing and communication, is an IEEE Fellow, is an ACM Fellow, was a Coeditor-in-Chief of the Journal of Parallel and Distributed Computing, and was on the Editorial Boards of both the IEEE Transactions on Parallel and Distributed Systems and the IEEE Transactions on Computers. He was Program Chair/Co-Chair of three major international conferences, General Chair/Co-Chair of four international conferences, and Chair/Co-Chair of five workshops. He has been an international keynote speaker and tutorial lecturer, and has consulted for industry and government. David St. John is Chief Information Officer for WeatherFlow, Inc., a weather services company specializing in coastal weather observations and forecasts. He received a master’s degree in Engineering from the University of California, Irvine. He spent several years as the head of staff on the Management System for Heterogeneous Networks project in the Computer Science Department of the Naval Postgraduate School. His current relationship with cluster computing is as a user of the Regional Atmospheric Modeling System (RAMS), a numerical weather model developed at Colorado State University. WeatherFlow runs RAMS operationally on a Linux-based cluster. Cynthia Irvine is a Professor of Computer Science at the Naval Postgraduate School in Monterey, California. She received her Ph.D. from Case Western Reserve University and her B.A. in Physics from Rice University. She joined the faculty of the Naval Postgraduate School in 1994. Previously she worked in industry on the development of high assurance secure systems. In 2001, Dr. Irvine received the Naval Information Assurance Award. Dr. Irvine is the Director of the Center for Information Systems Security Studies and Research at the Naval Postgraduate School. She has served on special panels for NSF, DARPA, and OSD. In the area of computer security education Dr. Irvine has most recently served as the general chair of the Third World Conference on Information Security Education and the Fifth Workshop on Education in Computer Security. She co-chaired the NSF workshop on Cyber-security Workforce Needs Assessment and Educational Innovation and was a participant in the Computing Research Association/NSF sponsored Grand Challenges in Information Assurance meeting. She is a member of the editorial board of the Journal of Information Warfare and has served as a reviewer and/or program committee member of a variety of security related conferences. She has written over 100 papers and articles and has supervised the work of over 80 students. Professor Irvine is a member of the ACM, the AAS, a life member of the ASP, and a Senior Member of the IEEE. Timothy E. Levin is a Research Associate Professor at the Naval Postgraduate School. He has spent over 18 years working in the design, development, evaluation, and verification of secure computer systems, including operating systems, databases and networks. His current research interests include high assurance system design and analysis, development of models and methods for the dynamic selection of QoS security attributes, and the application of formal methods to the development of secure computer systems. Viktor K. Prasanna received his BS in Electronics Engineering from the Bangalore University and his MS from the School of Automation, Indian Institute of Science. He obtained his Ph.D. in Computer Science from the Pennsylvania State University in 1983. Currently, he is a Professor in the Department of Electrical Engineering as well as in the Department of Computer Science at the University of Southern California, Los Angeles. He is also an associate member of the Center for Applied Mathematical Sciences (CAMS) at USC. He served as the Division Director for the Computer Engineering Division during 1994–98. His research interests include parallel and distributed systems, embedded systems, configurable architectures and high performance computing. Dr. Prasanna has published extensively and consulted for industries in the above areas. He has served on the organizing committees of several international meetings in VLSI computations, parallel computation, and high performance computing. He is the Steering Co-chair of the International Parallel and Distributed Processing Symposium [merged IEEE International Parallel Processing Symposium (IPPS) and the Symposium on Parallel and Distributed Processing (SPDP)] and is the Steering Chair of the International Conference on High Performance Computing(HiPC). He serves on the editorial boards of the Journal of Parallel and Distributed Computing and the Proceedings of the IEEE. He is the Editor-in-Chief of the IEEE Transactions on Computers. He was the founding Chair of the IEEE Computer Society Technical Committee on Parallel Processing. He is a Fellow of the IEEE. Richard F. Freund is the originator of GridIQ’s network scheduling concepts that arose from mathematical and computing approaches he developed for the Department of Defense in the early 1980’s. Dr. Freund has over twenty-five years experience in computational mathematics, algorithm design, high performance computing, distributed computing, network planning, and heterogeneous scheduling. Since 1989, Dr. Freund has published over 45 journal articles in these fields. He has also been an editor of special editions of IEEE Computer and the Journal of Parallel and Distributed Computing. In addition, he is a founder of the Heterogeneous Computing Workshop, held annually in conjunction with the International Parallel Processing Symposium. Dr. Freund is the recipient of many awards, which includes the prestigious Department of Defense Meritorious Civilian Service Award in 1984 and the Lauritsen-Bennet Award from the Space and Naval Warfare Systems Command in San Diego, California.     

A task scheduling algorithm for arbitrarily-connected processors with awareness of link contention

In this paper, we present a new task scheduling algorithm, called Contention-Aware Scheduling (CAS) algorithm, with the objective of delivering good quality of schedules in low running-time by considering contention on links of arbitrarily-connected, heterogeneous processors. The CAS algorithm schedules tasks on processors and messages on links by considering the earliest finish time attribute with the virtual cut-through (VCT) or the store-and-forward (SAF) switching. There are three types of CAS algorithm presented in this paper, which differ in ordering the messages from immediate predecessor tasks. As part of the experimental study, the performance of the CAS algorithm is compared with two well-known APN (arbitrary processor network) scheduling algorithms. Experiments on the results of the synthetic benchmarks and the task graphs of the well-known problems clearly show that our CAS algorithm outperforms the related work with respect to performance (given in normalized schedule length) and cost (given in running time) to generate output schedules. Ali Fuat Alkaya received the B.Sc. degree in mathematics from Koc University, Istanbul, Turkey in 1998, and the M.Sc. degree in computer engineering from Marmara University, Istanbul, Turkey in 2002. He is currently a Ph.D. student in engineering management department at the same university. His research interests include task scheduling and analysis of algorithms. Haluk Rahmi Topcuoglu received the B.Sc. and M.Sc. degrees in computer engineering from Bogazici University, Istanbul, Turkey, in 1991 and 1993, respectively. He received the Ph.D. degree in computer science from Syracuse University in 1999. He has been on the faculty at Marmara University, Istanbul, Turkey since Fall 1999, where he is currently an Associate Professor in computer engineering department. His main research interests are task scheduling and mapping in parallel and distributed systems; parallel processing; evolutionary algorithms and their applicability for stationary and dynamic environments. He is a member of the ACM, the IEEE, and the IEEE Computer Society. e-mail: haluk@eng.marmara.edu.tr e-mail: falkaya@eng.marmara.edu.tr     

Discretionary Caching for I/O on Clusters

I/O bottlenecks are already a problem in many large-scale applications that manipulate huge datasets. This problem is expected to get worse as applications get larger, and the I/O subsystem performance lags behind processor and memory speed improvements. At the same time, off-the-shelf clusters of workstations are becoming a popular platform for demanding applications due to their cost-effectiveness and widespread deployment. Caching I/O blocks is one effective way of alleviating disk latencies, and there can be multiple levels of caching on a cluster of workstations. Previous studies have shown the benefits of caching—whether it be local to a particular node, or a shared global cache across the cluster—for certain applications. However, we show that while caching is useful in some situations, it can hurt performance if we are not careful about what to cache and when to bypass the cache. This paper presents compilation techniques and runtime support to address this problem. These techniques are implemented and evaluated on an experimental Linux/Pentium cluster running a parallel file system. Our results using a diverse set of applications (scientific and commercial) demonstrate the benefits of a discretionary approach to caching for I/O subsystems on clusters, providing as much as 48% savings in overall execution time over indiscriminately caching everything in some applications. Parts of this paper have appeared in the Proceedings of the 3rd IEEE/ACM Symposium on Cluster Computing and the Grid (CCGrid'03). This paper is an extension of these prior results, and includes a more extensive performance evaluation. Murali Vilayannur is a Ph.D. student in the Department of Computer Science and Engineering at The Pennsylvania State University. His research interests are in High-Performance Parallel I/O, File Systems, Virtual Memory Algorithms and Operating Systems. Anand Sivasubramaniam received his B.Tech. in Computer Science from the Indian Institute of Technology, Madras, in 1989, and the M.S. and Ph.D. degrees in Computer Science from the Georgia Institute of Technology in 1991 and 1995 respectively. He has been on the faculty at The Pennsylvania State University since Fall 1995 where he is currently an Associate Professor. Anand's research interests are in computer architecture, operating systems, performance evaluation, and applications for both high performance computer systems and embedded systems. Anand's research has been funded by NSF through several grants, including the CAREER award, and from industries including IBM, Microsoft and Unisys Corp. He has several publications in leading journals and conferences, and is on the editorial board of IEEE Transactions on Computers and IEEE Transactions on Parallel and Distributed Systems. He is a recipient of the 2002 IBM Faculty Award. Anand is a member of the IEEE, IEEE Computer Society, and ACM. Mahmut Kandemir received the B.Sc. and M.Sc. degrees in control and computer engineering from Istanbul Technical University, Istanbul, Turkey, in 1988 and 1992, respectively. He received the Ph.D. from Syracuse University, Syracuse, New York in electrical engineering and computer science, in 1999. He has been an assistant professor in the Computer Science and Engineering Department at the Pennsylvania State University since August 1999. His main research interests are optimizing compilers, I/O intensive applications, and power-aware computing. He is a member of the IEEE and the ACM. Rajeev Thakur is a Computer Scientist in the Mathematics and Computer Science Division at Argonne National Laboratory. He received a B.E. from the University of Bombay, India, in 1990, M.S. from Syracuse University in 1992, and Ph.D. from Syracuse University in 1995, all in computer engineering. His research interests are in the area of high-performance computing in general and high-performance networking and I/O in particular. He was a member of the MPI Forum and participated actively in the definition of the I/O part of the MPI-2 standard. He is the author of a widely used, portable implementation of MPI-IO, called ROMIO. He is also a co-author of the book “Using MPI-2: Advanced Features of the Message Passing Interface” published by MIT Press. Robert Ross received his Ph.D. in Computer Engineering from Clemson University in 2000. He is now an Assistant Scientist in the Mathematics and Computer Science Division at Argonne National Laboratory. His research interests are in message passing and storage systems for high performance computing environments. He is the primary author and lead developer for the Parallel Virtual File System (PVFS), a parallel file system for Linux clusters. Current projects include the ROMIO MPI-IO implementation, PVFS, PVFS2, and the MPICH2 implementation of the MPI message passing interface.     

Exploiting redundancy to boost performance in a RAID-10 style cluster-based file system

While aggregating the throughput of existing disks on cluster nodes is a cost-effective approach to alleviate the I/O bottleneck in cluster computing, this approach suffers from potential performance degradations due to contentions for shared resources on the same node between storage data processing and user task computation. This paper proposes to judiciously utilize the storage redundancy in the form of mirroring existed in a RAID-10 style file system to alleviate this performance degradation. More specifically, a heuristic scheduling algorithm is developed, motivated from the observations of a simple cluster configuration, to spatially schedule write operations on the nodes with less load among each mirroring pair. The duplication of modified data to the mirroring nodes is performed asynchronously in the background. The read performance is improved by two techniques: doubling the degree of parallelism and hot-spot skipping. A synthetic benchmark is used to evaluate these algorithms in a real cluster environment and the proposed algorithms are shown to be very effective in performance enhancement. Yifeng Zhu received his B.Sc. degree in Electrical Engineering in 1998 from Huazhong University of Science and Technology, Wuhan, China; the M.S. and Ph.D. degree in Computer Science from University of Nebraska – Lincoln in 2002 and 2005 respectively. He is an assistant professor in the Electrical and Computer Engineering department at University of Maine. His main research interests are cluster computing, grid computing, computer architecture and systems, and parallel I/O storage systems. Dr. Zhu is a Member of ACM, IEEE, the IEEE Computer Society, and the Francis Crowe Society. Hong Jiang received the B.Sc. degree in Computer Engineering in 1982 from Huazhong University of Science and Technology, Wuhan, China; the M.A.Sc. degree in Computer Engineering in 1987 from the University of Toronto, Toronto, Canada; and the PhD degree in Computer Science in 1991 from the Texas A&M University, College Station, Texas, USA. Since August 1991 he has been at the University of Nebraska-Lincoln, Lincoln, Nebraska, USA, where he is Professor and Vice Chair in the Department of Computer Science and Engineering. His present research interests are computer architecture, parallel/distributed computing, cluster and Grid computing, computer storage systems and parallel I/O, performance evaluation, real-time systems, middleware, and distributed systems for distance education. He has over 100 publications in major journals and international Conferences in these areas and his research has been supported by NSF, DOD and the State of Nebraska. Dr. Jiang is a Member of ACM, the IEEE Computer Society, and the ACM SIGARCH. Xiao Qin received the BS and MS degrees in computer science from Huazhong University of Science and Technology in 1992 and 1999, respectively. He received the PhD degree in computer science from the University of Nebraska-Lincoln in 2004. Currently, he is an assistant professor in the department of computer science at the New Mexico Institute of Mining and Technology. He had served as a subject area editor of IEEE Distributed System Online (2000–2001). His research interests are in parallel and distributed systems, storage systems, real-time computing, performance evaluation, and fault-tolerance. He is a member of the IEEE. Dan Feng received the Ph.D degree from Huazhong University of Science and Technology, Wuhan, China, in 1997. She is currently a professor of School of Computer, Huazhong University of Science and Technology, Wuhan, China. She is the principal scientist of the the National Grand Fundamental Research 973 Program of China “Research on the organization and key technologies of the Storage System on the next generation Internet.” Her research interests include computer architecture, storage system, parallel I/O, massive storage and performance evaluation. David Swanson received a Ph.D. in physical (computational) chemistry at the University of Nebraska-Lincoln (UNL) in 1995, after which he worked as an NSF-NATO postdoctoral fellow at the Technical University of Wroclaw, Poland, in 1996, and subsequently as a National Research Council Research Associate at the Naval Research Laboratory in Washington, DC, from 1997–1998. In 1999 he returned to UNL where he directs the Research Computing Facility and currently serves as an Assistant Research Professor in the Department of Computer Science and Engineering. The Office of Naval Research, the National Science Foundation, and the State of Nebraska have supported his research in areas such as large-scale scientific simulation and distributed systems.     

Distributed shared arrays: A distributed virtual machine with mobility support for reconfiguration

Distributed Shared Arrays (DSA) is a distributed virtual machine that supports Java-compliant multithreaded programming with mobility support for system reconfiguration in distributed environments. The DSA programming model allows programmers to explicitly control data distribution so as to take advantage of the deep memory hierarchy, while relieving them from error-prone orchestration of communication and synchronization at run-time. The DSA system is developed as an integral component of mobility support middleware for Grid computing so that DSA-based virtual machines can be reconfigured to adapt to the varying resource supplies or demand over the course of a computation. The DSA runtime system also features a directory-based cache coherence protocol in support of replication of user-defined sharing granularity and a communication proxy mechanism for reducing network contention. System reconfiguration is achieved by a DSA service migration mechanism, which moves the DSA service and residing computational agents between physical servers for load balancing and fault resilience. We demonstrate the programmability of the model in a number of parallel applications and evaluate its performance by application benchmark programs, in particular, the impact of the coherence granularity and service migration overhead. Song Fu received the BS degreee in computer science from Nanjing University of Aeronautics and Astronautics, China, in 1999, and the MS degree in computer science from Nanjing University, China, in 2002. He is currently a PhD candidate in computer engineering at Wayne State University. His research interests include the resource management, security, and mobility issues in wide-area distributed systems. Cheng-Zhong Xu received the BS and MS degrees in computer science from Nanjing University in 1986 and 1989, respectively, and the Ph.D. degree in computer science from the University of Hong Kong in 1993. He is an Associate Professor in the Department of Electrical and Computer Engineer of Wayne State University. His research interests lie in distributed are in distributed and parallel systems, particularly in resource management for high performance cluster and grid computing and scalable and secure Internet services. He has published more than100 peer-reviewed articles in journals and conference proceedings in these areas. He is the author of the book Scalable and Secure Internet Services and Architecture (CRC Press, 2005) and a co-author of the book Load Balancing in Parallel Computers: Theory and Practice (Kluwer Academic, 1997). He serves on the editorial boards of J. of Parallel and Distributed Computing, J. of Parallel, Emergent, and Distributed Systems, J. of High Performance Computing and Networking, and J. of Computers and Applications. He was the founding program co-chair of International Workshop on Security in Systems and Networks (SSN), the general co-chair of the IFIP 2006 International Conference on Embedded and Ubiquitous Computing (EUC06), and a member of the program committees of numerous conferences. His research was supported in part by the US National Science Foundation, NASA, and Cray Research. He is a recipient of the Faculty Research Award of Wayne State University in 2000, the Presidents Award for Excellence in Teaching in 2002, and the Career Development Chair Award in 2003. He is a senior member of the IEEE. Brian A. Wims was born in Washington, DC in 1967. He received the Bachelor of Science in Electrical Engineering from GMI-EMI (now called Kettering University) in 1990; and Master of Science in Computer Engineering from Wayne State University in 1999. His research interests are primarily in the fields of parallel and distributed systems with applications in Mobile Agent technologies. From 1990–2001 he worked in various Engineering positions in General Motors, including Electrical Analysis, Software Design, and Test and Development. In 2001, he joined the General Motors IS&S department where he is currently a Project Manager in the Computer Aided Test group. Responsibilities include managing the development of test automation applications in the Electrical, EMC, and Safety Labs. Ramzi Basharahil was born in Aden, Yemen in 1972. He received the Bachelor of Science degree in Electrical Engineering from the United Arab Emirates University. He graduated top of his engineering graduated class of 1997. He obtained Master of Science degree in 2001 from Wayne State University in the Department of Electrical and Computer Engineering. His main research interests are primarily in the fields of parallel and distributed systems with applications to distributed processing across cluster of servers. From 1997 to 1998, he worked as a Teaching Assistant in the Department of Electrical Engineering at the UAE University. In 2000, he joined Internet Security Systems as a security software engineer. He later joined NetIQ Corporation in 2002 and still working since then. He is leading the security events trending and events management software development where he is involved in designing and the implementing event/log managements products.     

Impact of Admission and Cache Replacement Policies on Response Times of Jobs on Data Grids

Caching techniques have been used widely to improve the performance gaps of storage hierarchies in computing systems. Little is known about the impact of policies on the response times of jobs that access and process very large files in data grids, particularly when data and computations on the data have to be co-located on the same host. In data intensive applications that access large data files over wide area network environment, such as data-grids, the combination of policies for job servicing (or scheduling), caching and cache replacement can significantly impact the performance of grid jobs. We present preliminary results of a simulation study that combines an admission policy with a cache replacement policy when servicing jobs submitted to a storage resource manager.The results show that, in comparison to a first come first serve policy, the response times of jobs are significantly improved, for practical limits of disk cache sizes, when the jobs that are back-logged to access the same files are taken into consideration in scheduling the next file to be retrieved into the disk cache. Not only are the response times of jobs improved, but also the metric measures for caching policies, such as the hit ratio and the average cost per retrieval, are improved irrespective of the cache replacement policy used. Ekow Otoo is research staff scientist with the scientific data management group at Lawrence Berkeley National Laboratory, University of California, Berkeley. He received his B.Sc. degree in Electrical Engineering from the University of Science and Technology, Kumasi, Ghana and a post graduate diploma in Computer Science from the University of Ghana, Legon. In 1977, he received his M.Sc. degree in Computer Science from the University of Newcastle Upon Tyne in Britain and his Ph.D. degree in Computer Science from McGill University, Montreal, Canada in 1983. He joined the faculty of the School of Computer Science, Carleton University, in 1983 and from 1987 to 1999, he was a tenured faculty member of the School of Computer Science, Carleton University, Ottawa, Canada. He has served as research consultant to Bell Northern Research, Ottawa, Canada, and as a research project consultant to the GIS Division, Geomatics Canada, Natural Resources Canada, from 1990 to 1998. Ekow Otoo is a member of the ACM and IEEE. His research interests include database management systems, data structures and algorithms, parallel I/O for high performance computing, parallel and distributed computing. Doron Rotem is currently a senior staff scientist and a member of the Data Management group at the Lawrence Berkeley National Lab. His research interests include Grid Computing, Workflow, Scientific Data Management and Paralled and Distributed Computing and Algorithms. He has published over 80 papers in international journals and conferences in these areas. Prior to that, Dr Rotem co-founded and served as a CTO of a startup company, called CommerceRoute, that made software products in the area of workflow and data integration and before that, he was an Associate Professor in the Department of Computer Science, University of Waterloo, Canada. Dr. Rotem holds a B.Sc degree in Mathematics and Statistics from the Hebrew University, Jerusalem, Israel and a Ph.D. in Computer Science from the University of the Witwatersrand, Johannesburg, South Africa. Arie Shoshani is a senior staff scientist at Lawrence Berkeley National Laboratory. He joined LBNL in 1976. He heads the Scientific Data Management Group. He received his Ph.D. from Princeton University in 1969. From 1969 to 1976, he was a researcher at System Development Corporation, where he worked on the Network Control Program for the ARPAnet, distributed databases, database conversion, and natural language interfaces to data management systems. His current areas of work include data models, query languages, temporal data, statistical and scientific database management, storage management on tertiary storage, and grid storage middleware. Arie is also the director of a Scientific Data Management (SDM) Integrated Software Infrastructure Center (ISIC), one of seven centers selected by the SciDAC program at DOE in 2001. In this capacity, he is coordinating the work of collaborators from 4 DOE laboratories and 4 universities (see: http://sdmcenter.lbl.gov). Dr. Shoshani has published over 65 technical papers in refereed journals and conferences, chaired several workshops, conferences, and panels in database management; and served on numerous program committees for various database conferences. He also served as an associate editor for the ACM Transactions on Database Systems. He was elected a member of the VLDB Endowment Board, served as the Publication Board Chairperson for the VLDB Journal, and as the Vice-President of the VLDB Endowment. His home page is http://www.lbl.gov/arie.     

IEEE 802.11b Ad Hoc Networks: Performance Measurements

In this paper we investigate the performance of IEEE 802.11b ad hoc networks by means of an experimental study. An extensive literature, based on simulation studies, there exists on the performance of IEEE 802.11 ad hoc networks. Our analysis reveals several aspects that are usually neglected in previous simulation studies. Firstly, since different transmission rates are used for control and data frames, different transmission ranges and carrier-sensing ranges may exist at the same time in the network. In addition, the transmission ranges are in practice much shorter than usually assumed in simulation analysis, not constant but highly variable (even in the same session) and depends on several factors. Finally, the results presented in this paper indicate that for correctly understanding the behavior of an 802.11b network operating in ad hoc mode, several different ranges must be considered. In addition to the transmission range, the physical carrier sensing range is very important. The transmission range is highly dependent on the data rate and is up to 100 m, while the physical carrier sensing range is almost independent from the data rate and is approximately 200 m. Furthermore, even though stations are outside from their respective physical carrier sensing range, they may still interfere if their distance is lower than 350 m.Giuseppe Anastasi received the Laurea degree in Electronics Engineering and the Ph.D. degree in Computer Engineering both from the University of Pisa, Italy, in 1990 and 1995, respectively. He is currently an associate professor of Computer Engineering at the Department of Information Engineering of the University of Pisa. His research interests include architectures and protocols for mobile computing, energy management, QoS in mobile networks, and ad hoc networks. He was a co-editor of the book Advanced Lectures in Networking (LNCS 2497, Springer, 2002), and published more than 50 papers, both in international journals and conference proceedings, in the area of computer networking. He served in the TPC of several international conferences including IFIP Networking 2002 and IEEE PerCom 2003. He is a member of the IEEE Computer Society.Eleonora Borgia received the Laurea degree in Computer Engineering from the University of Pisa, Italy, in 2002. She is currently working toward her Ph.D. degree at the IIT Institute of the Italian National Research Council (CNR). Her research interests are in the area of the wireless and mobile networks with particular attention to MAC protocols and routing algorithms for ad hoc networks.Marco Conti received the Laurea degree in Computer Science from the University of Pisa, Italy, in 1987. In 1987 he joined the Italian National Research Council (CNR). He is currently a senior researcher at CNR-IIT. His research interests include Internet architecture and protocols, wireless networks and ad hoc networking, mobile computing, and QoS in packet switching networks. He co-authored the book Metropolitan Area Networks (Springer, London, 1997), and published in journal and conference proceedings more than 100 research papers related to design, modeling, and performance evaluation of computer-network architectures and protocols. He served as the technical program committee chair of the IFIP-TC6 conferences Networking 2002 and PWC 2003, and technical program committee co-chair of ACM WoWMoM 2002. He is serving as technical program committee co-chair of the IEEE Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2005). He served as guest editor for the Cluster Computing Journal (special issue on Mobile Ad Hoc Networking), IEEE Transactions on Computers (special issue on Quality of Service issues in Internet Web Services), and ACM/Kluwer Mobile Networks & Applications Journal (special issue on Mobile Ad hoc Networks). He is member of IFIP WGs 6.2, 6.3 and 6.8.Enrico Gregori received the Laurea in electronic engineering from the University of Pisa in 1980. He joined CNUCE, an institute of the Italian National Research Council (CNR) in 1981. He is currently a CNR research director. In 1986 he held a visiting position in the IBM research center in Zurich working on network software engineering and on heterogeneous networking. He has contributed to several national and international projects on computer networking. He has authored more than 100 papers in the area of computer networks and has published in international journals and conference proceedings and is co-author of the book Metropolitan Area Networks (Springer, London, 1997). He was the General Chair of the IFIP TC6 conferences: Networking2002 and PWC2003 (Personal Wireless Communications). He served as guest editor for the Networking2002 journal special issues on: Performance Evaluation, Cluster Computing and ACM/Kluwer Wireless Networks Journals. He is a member of the board of directors of the Create-Net association, an association with several Universities and research centres that is fostering research on networking at European level. He is on the editorial board of the Cluster Computing, of the Computer Networks and of the Wireless Networks Journals. His current research interests include: Wireless access to Internet, Wireless LANs, Quality of service in packet-switching networks, Energy saving protocols, Evolution of TCP/IP protocols.     

Exploring the effects of truncated,pooled and sexed data in distance sampling estimation of breeding bird abundance

Capsule Field methods used by the UK's Breeding Bird Survey (BBS) provide a practical approach to estimating breeding bird abundance and this paper discusses how they might be adapted to increase accuracy.

Aims Using Salisbury Plain as a case study, examine the use of distance sampling to produce estimates of breeding bird abundance.

Methods During 2005, 157 1 km squares were surveyed on Salisbury Plain using the UK’s BBS methods, with the exception that all birds were sexed whenever possible and allocated to one of five distance bands (0–10 m/10–25 m/25–100 m/100–250 m/ >250 m). Data were modelled to investigate the effects of truncated, pooled and sexed bird data in estimating breeding populations.

Results Pooling of the inner distance bands made little difference to estimates, while truncation over 100 m affected them by up to 25%, generally leading to an increase in density and the width of the confidence limits. The national BBS does not distinguish between bird sexes and therefore any density estimate produced relates to individuals. Our analysis suggests that halving the number of individuals (assuming an equal sex ratio) could lead to significant underestimation of population. This is particularly the case for species where there are differences in detectability between sexes or skewed sex ratios. In such cases, the density of males may represent a more accurate assessment of the population.

Conclusions Bird surveys incorporate distance sampling because it assesses changes in detection probability and this paper suggests how these methods might be adapted to increase accuracy. Changes include increasing both survey effort (e.g. number of visits or distance covered), the number of distance bands, and recording sexed bird data. Numbers of pairs or territories could then be estimated by either halving the density of individuals, or using the density of males, whichever is highest. These suggestions have not been tested against a known population and further work is desirable.     

Distributed File System Virtualization Techniques Supporting On-Demand Virtual Machine Environments for Grid Computing

This paper presents a data management solution which allows fast Virtual Machine (VM) instantiation and efficient run-time execution to support VMs as execution environments in Grid computing. It is based on novel distributed file system virtualization techniques and is unique in that: (1) it provides on-demand cross-domain access to VM state for unmodified VM monitors; (2) it enables private file system channels for VM instantiation by secure tunneling and session-key based authentication; (3) it supports user-level and write-back disk caches, per-application caching policies and middleware-driven consistency models; and (4) it leverages application-specific meta-data associated with files to expedite data transfers. The paper reports on its performance in wide-area setups using VMware-based VMs. Results show that the solution delivers performance over 30% better than native NFS and with warm caches it can bring the application-perceived overheads below 10% compared to a local-disk setup. The solution also allows a VM with 1.6 GB virtual disk and 320 MB virtual memory to be cloned within 160 seconds for the first clone and within 25 seconds for subsequent clones. Ming Zhao is a PhD candidate in the department of Electrical and Computer Engineering and a member of the Advance Computing and Information Systems Laboratory, at University of Florida. He received the degrees of BE and ME from Tsinghua University. His research interests are in the areas of computer architecture, operating systems and distributed computing. Jian Zhang is a PhD student in the Department of Electrical and Computer Engineering at University of Florida and a member of the Advance Computing and Information Systems Laboratory (ACIS). Her research interest is in virtual machines and Grid computing. She is a member of the IEEE and the ACM. Renato J. Figueiredo received the B.S. and M.S. degrees in Electrical Engineering from the Universidade de Campinas in 1994 and 1995, respectively, and the Ph.D. degree in Electrical and Computer Engineering from Purdue University in 2001. From 2001 until 2002 he was on the faculty of the School of Electrical and Computer Engineering of Northwestern University at Evanston, Illinois. In 2002 he joined the Department of Electrical and Computer Engineering of the University of Florida as an Assistant Professor. His research interests are in the areas of computer architecture, operating systems, and distributed systems.     

Whole-population trends in pathology-confirmed cancer incidence in Northern Ireland,Scotland and Wales during the SARS-CoV-2 pandemic: A retrospective observational study

IntroductionThe COVID-19 epidemic interrupted normal cancer diagnosis procedures. Population-based cancer registries report incidence at least 18 months after it happens. Our goal was to make more timely estimates by using pathologically confirmed cancers (PDC) as a proxy for incidence. We compared the 2020 and 2021 PDC with the 2019 pre-pandemic baseline in Scotland, Wales, and Northern Ireland (NI).MethodsNumbers of female breast (ICD-10 C50), lung (C33–34), colorectal (C18–20), gynaecological (C51–58), prostate (C61), head and neck (C00-C14, C30–32), upper gastro-intestinal (C15–16), urological (C64–68), malignant melanoma (C43), and non-melanoma skin (NMSC) (C44) cancers were counted. Multiple pairwise comparisons generated incidence rate ratios (IRR).ResultsData were accessible within 5 months of the pathological diagnosis date. Between 2019 and 2020, the number of pathologically confirmed malignancies (excluding NMSC) decreased by 7315 (14.1 %). Scotland experienced early monthly declines of up to 64 % (colorectal cancers, April 2020 versus April 2019). Wales experienced the greatest overall change in 2020, but Northern Ireland experienced the quickest recovery. The pandemic's effects varied by cancer type, with no significant change in lung cancer diagnoses in Wales in 2020 (IRR 0.97 (95 % CI 0.90–1.05)), followed by an increase in 2021 (IRR 1.11 (1.03–1.20).ConclusionPDC are useful in reporting cancer incidence quicker than cancer registrations. Temporal and geographical differences between participating countries mirrored differences in responses to the COVID-19 pandemic, indicating face validity and the potential for quick cancer diagnosis assessment. To verify their sensitivity and specificity against the gold standard of cancer registrations, however, additional research is required.     

Discovering likely invariants of distributed transaction systems for autonomic system management

Large amount of monitoring data can be collected from distributed systems as the observables to analyze system behaviors. However, without reasonable models to characterize systems, we can hardly interpret such monitoring data effectively for system management. In this paper, a new concept named flow intensity is introduced to measure the intensity with which internal monitoring data reacts to the volume of user requests in distributed transaction systems. We propose a novel approach to automatically model and search relationships between the flow intensities measured at various points across the system. If the modeled relationships hold all the time, they are regarded as invariants of the underlying system. Experimental results from a real system demonstrate that such invariants widely exist in distributed transaction systems. Further we discuss how such invariants can be used to characterize complex systems and support autonomic system management. Guofei Jiang received the B.S. and Ph.D. degrees in electrical and computer engineering from Beijing Institute of Technology, China, in 1993 and 1998, respectively. During 1998–2000, he was a postdoctoral fellow in computer engineering at Dartmouth College, NH. He is currently a research staff member with the Robust and Secure Systems Group in NEC Laboratories America at Princeton, NJ. During 2000–2004, he was a research scientist in the Institute for Security Technology Studies at Dartmouth College. His current research focus is on distributed system, dependable and secure computing, system and information theory. He has published over 50 technical papers in these areas. He is an associate editor of IEEE Security and Privacy magazine and has served in the program committees of many conferences. Haifeng Chen received the BEng and MEng degrees, both in automation, from Southeast University, China, in 1994 and 1997 respectively, and the PhD degree in computer engineering from Rutgers University, New Jersey, in 2004. He has worked as a researcher in the Chinese national research institute of power automation. He is currently a research staff member at NEC laboratory America, Princeton, NJ. His research interests include data mining, autonomic computing, pattern recognition and robust statistics. Kenji Yoshihira received the B.E. in EE at University of Tokyo in 1996 and designed processor chips for enterprise computer at Hitachi Ltd. for five years. He employed himself in CTO at Investoria Inc. in Japan to develop an Internet service system for financial information distribution through 2002 and received the M.S. in CS at New York University in 2004. He is currently a research staff member with the Robust and Secure Systems Group in NEC Laboratories America, inc. in NJ. His current research focus is on distributed system and autonomic computing.     

Breeding status of Merlins Falco columbarius in the UK in 2008

Capsule The third national Merlin survey estimated a UK population of 1162 breeding pairs (95% CI: 891–1462).

Aims To estimate the number of breeding Merlins (with associated 95% confidence intervals) in the UK and the four countries (Scotland, England, Wales and Northern Ireland), and to compare these with the relevant estimates from the 1993–94 Merlin survey. In addition, to calculate estimates of change for several regional populations with complete survey coverage during both national surveys.

Methods A subset of 10-km squares (Raptor Study Group squares and randomly sampled squares) was surveyed across the breeding distribution of Merlins in the UK using standardised methods devised during the 1993–94 national survey.

Results The population estimate for Merlins in the UK was 1162 breeding pairs, and in Britain was 1128 pairs (95% CI: 849–1427), which although 13% lower, was not significantly different from the British estimate of the 1993–94 survey. Scotland held the bulk (733 pairs) of the UK Merlin population, and smaller numbers of 301 pairs, 94 pairs and 32 pairs were estimated for England, Wales and Northern Ireland, respectively. The population estimate for Wales may have been biased upwards by low coverage in the south of the country. Marked declines were noted in several regional Merlin populations, particularly in areas of northern England.

Conclusions The 2008 Merlin survey suggests that the population in Britain has remained relatively stable since 1993–94, but with local declines, particularly in northern England. Currently, little is known about important drivers of regional population change in Merlins, but changes in land-use, prey populations and climate are likely to be important factors.     

On Explicit Congestion Notification for Stream Control Transmission Protocol in Lossy Networks

As a congestion avoidance mechanism, Explicit Congestion Notification (ECN) is designed to inform a data source to react to potential congestion early. Currently, the new transport protocol, Stream Control Transmission Protocol (SCTP), is not ECN-capable. An ECN-capable SCTP is proposed in this paper, which is bandwidth-efficient and robust to non-congestion losses. An SCTP source needs to adjust its congestion window when receiving ECN messages. We find the optimal value of the congestion window for an SCTP source in response to ECN messages, and develop a simple and practical method to achieve this optimal congestion window. Both simulation results and analysis are provided to support the effectiveness of the proposed ECN mechanism for SCTP. The simplified method in achieving the optimal congestion window is attractive because the total goodput performance of SCTP associations or the bottleneck link utilization is not sensitive to the window reduction policies when the network load is heavy. Using complicated methods to fine-tune SCTP or TCPs congestion window in response to congestion indications may not be worth the increase in complexity of the protocol.Prepared through collaborative participation in the Communications and Networks Consortium sponsored by the U.S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon.Guanhua Ye received the B.E. degree in Information & Electronic Technology from Zhejiang University, China, in 1997 and M.E. degree in Communication & Information Systems from China Academy of Telecommunications Technology in 2000. He is currently working toward the Ph.D. degree in Electrical Engineering at City College and Graduate Center of City University of New York.His research interests are in computer networks, congestion control, ad hoc networks, voice over IP and multimedia communications.Tarek N. Saadawi received the B.Sc. and the M.Sc. from Cairo University Egypt and the Ph.D from the University of Maryland, College Park (all in Electrical Engineering). Since 1980 he has been with the Electrical Engineering Department, The City University of New York, City College. His current research interests are telecommunications network, high-speed networks, multimedia networks, AD-HOC networks and packet radio networks. He has published extensively in the area of telecommunications networks. He is a Co-author of the book, Fundamentals of Telecommunication Networks, John Wiley & Sons, 1994. He is also the lead author of Egypt Telecommunications Infrastructure Master Plan covering the fiber network, IP/ATM, DSL and the wireless local loop. Dr. Saadawi is a Former Chairman of IEEE Computer Society of New York City (1986–87). He has received IEEE Region 1 Award, 1987, and the Nippon Telegraph and Telephone (NTT) of America for research on Broadband Telecommunication Networks.Dr. Myung Jong Lee received the B.S from Seoul National University in Korea and M.S and Ph.D degrees in electrical engineering from Columbia University, 1986 and 1990 respectively. He joined the Department of Electrical Engineering, City College and Graduate Center of City University of New York, where he is currently an associate professor.His recent researches focus on various aspects of wireless ad hoc networks, sensor networks, and personal area networks. He has published over 50 refereed journal and conference papers. He is the Director of Samsung-CUNY Joint Laboratory on Sensor Networks. Dr. Lee received CUNYs Excellence Performance Award in 1999. Dr. Lee is a senior member of IEEE, and served many IEEE and other conferences as program committee member and session chair, and also actively participates in ZigBee Alliance and IEEE1451 Smart Sensor WG.     

Method learning caused a first‐time observer effect in a newly started breeding bird survey

Capsule A first‐time observer effect in the new French breeding bird survey (BBS) was found to result from new observers learning how to use the point count method on randomly selected sites.

Aims To estimate the first‐year effect in a newly started BBS, to look for correlates and test for a temporal trend in learning.

Methods Trends of 105 species were estimated using data from 2001–2007 obtained by 1100 observers conducting point counts over 1535 randomly selected squares. I estimated the average increase in detected numbers between the first and all subsequent years of survey at a site.

Results Observers counted 4.3% more birds in subsequent years than during the initial year of survey. This first‐year effect decreased from 2001 to 2007 (by an average of 2% per year). It was not related to most variables known to influence species detection probability. Only species with songs of lower sound frequencies (ranging from 0.5 to 8 kHz here) displayed a greater increase in locally detected numbers.

Conclusion The detected first‐year effect was the result of method learning by new observers who had not previously conducted point counts or visited randomly selected sites. The learning effect was larger for species with songs of lower sound frequency which are harder to hear during the dawn chorus.     

Average Waiting Time of Clusterhead Controlled Token for Virtual Base Station On-Demand in MANETs

A wireless mobile Ad hoc network (MANET) is a collection of wireless mobile hosts forming nodes that are arbitrarily and randomly changing their locations and communicating without the aid of any centralized administration or standard support services. Ad hoc cluster-based routing protocols establish a dynamic wireless mobile infrastructure to mimic the operation of the fixed infrastructure in cellular networks. A clusterhead is elected from a set of nominees, based on an agreed upon rule, to act as a temporary base station within its zone or autonomous system. Mobile stations elected as clusterheads are used to track other mobile stations in the ad hoc network. In each cluster, we use the clusterhead controlled token to assign the channel among contending Mobile Terminals (MTs). A clusterhead controlled token supports multiple class of services and minimizes collisions. In this paper, we derive formulas to calculate the average waiting time for a packet, in order to get transmitted. In our study, we use two polling schemes, namely: Exhaustive polling and Partially Gated polling controlled token.Tarek Sheltami is currently an assistant professor at the Computer Engineering Department at King Fahd University of Petroleum and Minerals (KFUPM) Dhahran, Kingdom of Saudi Arabia. He joined the department on September, 2004. Before joining the KFUPM, Dr. Sheltami was a research associate professor at the School of Information Technology and Engineering (SITE), University of Ottawa, Ontario, Canada. He has two years of industrial experience at GamaEng Inc (2002–2004). He is the co-author of the Warning Energy Aware Clusterhead (WEAC) infrastructure protocol and the Virtual Base Station On-demand (VBS-O) routing protocol. Dr. Sheltami has been a member of a technical program and organizing committees of several international IEEE conferences. Dr. Sheltamis research interests are in the area of wireless communications, wireless ad hoc and sensors networks, mobile infrastructure protocols, network control/mobility management, UMTS, and performance evaluation of wireless communication networks.Hussein Mouftah joined the School of Information Technology and Engineering (SITE) of the University of Ottawa in September 2002 as a Canada Research Chair (Tier 1) Professor in Optical Networks. He has been with the Department of Electrical and Computer Engineering at Queens University (1979–2002), where he was prior to his departure a Full Professor and the Department Associate Head. He has three years of industrial experience mainly at Bell Northern Research of Ottawa, now Nortel Networks (1977–79). He has spent three sabbatical years also at Nortel Networks (1986–87, 1993–94, and 2000–01), always conducting research in the area of broadband packet switching networks, mobile wireless networks and quality of service over the optical Internet. He served as Editor-in-Chief of the IEEE Communications Magazine (1995–97) and IEEE Communications Society Director of Magazines (1998–99) and Chair of the Awards Committee (2002–2003). He is a Distinguished Speaker of the IEEE Communications Society since 2000. Dr. Mouftah is the author or coauthor of five books, 22 book chapters and more than 700 technical papers and 8 patents in this area. He is the recipient of the 1989 Engineering Medal for Research and Development of the Association of Professional Engineers of Ontario (PEO), and the Ontario Distinguished Researcher Award of the Ontario Innovation Trust. He is the joint holder of the Best Paper Award for a paper presented at SPECTS 2002, and the Outstanding Paper Award for papers presented at the IEEE HPSR 2002 and the IEEE ISMVLõ1985. Also he is the joint holder of a Honorable Mention for the Frederick W. Ellersick Price Paper Award for Best Paper in the IEEE Communications Magazine in 1993. He is the recipient of the IEEE Canada (Region 7) Outstanding Service Award (1995). Also he is the recipient of the 2004 IEEE Communications Society Edwin Howard Armstrong Achievement Award, and the 2004 George S. Glinski Award for Excellence in Research of the Faculty of Engineering, University of Ottawa. Dr. Mouftah is a Fellow of the IEEE (1990), the Canadian Academy of Engineering (2003) and the Engineering Institute of Canada (2005).     

Improving the performance of I/O-intensive applications on clusters of workstations

Load balancing in a workstation-based cluster system has been investigated extensively, mainly focusing on the effective usage of global CPU and memory resources. However, if a significant portion of applications running in the system is I/O-intensive, traditional load balancing policies can cause system performance to decrease substantially. In this paper, two I/O-aware load-balancing schemes, referred to as IOCM and WAL-PM, are presented to improve the overall performance of a cluster system with a general and practical workload including I/O activities. The proposed schemes dynamically detect I/O load imbalance of nodes in a cluster, and determine whether to migrate some I/O load from overloaded nodes to other less- or under-loaded nodes. The current running jobs are eligible to be migrated in WAL-PM only if overall performance improves. Besides balancing I/O load, the scheme judiciously takes into account both CPU and memory load sharing in the system, thereby maintaining the same level of performance as existing schemes when I/O load is low or well balanced. Extensive trace-driven simulations for both synthetic and real I/O-intensive applications show that: (1) Compared with existing schemes that only consider CPU and memory, the proposed schemes improve the performance with respect to mean slowdown by up to a factor of 20; (2) When compared to the existing approaches that only consider I/O with non-preemptive job migrations, the proposed schemes achieve improvements in mean slowdown by up to a factor of 10; (3) Under CPU-memory intensive workloads, our scheme improves the performance over the existing approaches that only consider I/O by up to 47.5%. Xiao Qin received the BSc and MSc degrees in computer science from Huazhong University of Science and Technology in 1992 and 1999, respectively. He received the PhD degree in computer science from the University of Nebraska-Lincoln in 2004. Currently, he is an assistant professor in the department of computer science at the New Mexico Institute of Mining and Technology. His research interests include parallel and distributed systems, storage systems, real-time computing, performance evaluation, and fault-tolerance. He served on program committees of international conferences like CLUSTER, ICPP, and IPCCC. During 2000–2001, he was on the editorial board of The IEEE Distributed System Online. He is a member of the IEEE. Hong Jiang received the B.Sc. degree in Computer Engineering in 1982 from Huazhong University of Science and Technology, Wuhan, China; the M.A.Sc. degree in Computer Engineering in 1987 from the University of Toronto, Toronto, Canada; and the PhD degree in Computer Science in 1991 from the Texas A&M University, College Station, Texas, USA. Since August 1991 he has been at the University of Nebraska-Lincoln, Lincoln, Nebraska, USA, where he is Associate Professor and Vice Chair in the Department of Computer Science and Engineering. His present research interests are computer architecture, parallel/distributed computing, computer storage systems and parallel I/O, performance evaluation, middleware, networking, and computational engineering. He has over 70 publications in major journals and international Conferences in these areas and his research has been supported by NSF, DOD and the State of Nebraska. Dr. Jiang is a Member of ACM, the IEEE Computer Society, and the ACM SIGARCH and ACM SIGCOMM. Yifeng Zhu received the B.E. degree in Electrical Engineering from Huazhong University of Science and Technology in 1998 and the M.S. degree in computer science from University of Nebraska Lincoln (UNL) in 2002. Currently he is working towards his Ph.D. degree in the department of computer science and engineering at UNL. His main fields of research interests are parallel I/O, networked storage, parallel scheduling, and cluster computing. He is a student member of IEEE. David Swanson received a Ph.D. in physical (computational) chemistry at the University of Nebraska-Lincoln (UNL) in 1995, after which he worked as an NSF-NATO postdoctoral fellow at the Technical University of Wroclaw, Poland, in 1996, and subsequently as a National Research Council Research Associate at the Naval Research Laboratory in Washington, DC, from 1997–1998. In early 1999 he returned to UNL where he has coordinated the Research Computing Facility and currently serves as an Assistant Research Professor in the Department of Computer Science and Engineering. The Office of Naval Research, the National Science Foundation, and the State of Nebraska have supported his research in areas such as large-scale parallel simulation and distributed systems.     

C. O. Whitman and the American Society of Zoologists

C. O. Whitman (1842–1910) studied under Louis Agassiz,Anton Dohrn, and Rudolph Leuchart. Under the influence of E.S. Morse, Whitman served as the second professor of zoologyat the University of Tokyo (1880–81). For three yearshe was assistant to Alexander Agassiz at the Museum of ComparativeZoology. Between 1883 and 1886 Whitman was editor of the Departmentof Microscopy for the American Naturalist. He became the firstdirector of the Marine Biological Laboratory at Woods Hole,serving until 1908, and built that institution into an internationallyfamous center for education and research. He also became firstprofessor of Zoology at the University of Chicago where he remainedfor life. In 1887 he founded the Journal of Morphology, andlater Biological Lectures, and Zoological Bulletin which becamethe Biological Bulletin. His own research was in the fieldsof embryology, heredity, and evolution. In 1890 he, with colleagues,founded the American Morphological Society which became theAmerican Society of Zoologists over a period of 13 years (1901–13)by the union of regional groups. Whitman played a leading rolein the founding and early history of the Society.