A Distributed Approach to Estimate Link-Level Loss Rates
Network tomography aims to obtain link-level characteristics, such as loss rate and average delay of a link, by end-to-end measurement. A number of methods have been proposed to estimate the loss rate of a link by end-to-end measurement, all of them, in principle, are based on parametric statistics to identify unknown parameters. In addition, they all used the traditional centralized data processing techniques to complete the estimation, which is time-consuming and unscaleable. In this paper, we put forward a distributed method to tackle the scalability problem. The proposed method, instead of estimating link-level characteristics directly, estimate path level characteristics first that can be executed in parallel and can be achieved by a distributed system. The path level characteristics obtained can be used to identify link-level ones later. The proposed method has been proved to be an maximum likelihood estimate.

title: Fast handover in clustered wireless ATM
abstract: ATM networks can be extended to wireless networks by attaching wireless base stations to ATM networks, which allows mobile users to roam with little restriction. Due to the physical limitation, handovers become unavoidable when mobiles move from one area to another. As ATM networks are connection-oriented, connections have to be rerouted if a mobile device is moving out of its current cell. To have seamless communication, the handover process must be performed with small delay, minimal cell loss and no change in cell sequence. The authors propose an architecture to link ATM network to wireless networks. The proposed architecture is built on a hierarchical structure that groups cells into clusters. Different handover protocols are used, depending on whether a handover is in the same cluster or between clusters. In addition, the protocols take appropriate actions based on the type of communication. The performance of this protocol is superior to existing solutions in terms of speed and resource consumption.

title: A Hopfield neural network based task mapping method
abstract: With a prior knowledge of a program, static mapping aims to identify an optimal clustering strategy that can produce the best performance. In this paper we present a static method that uses Hopfield neural network to cluster the tasks of a parallel program for a given system. This method takes into account both load balancing and communication minimization. The method has been tested on a distributed shared memory system against other three clustering methods. Four programs, SOR, N-body, Gaussian Elimination and VQ, are used in the test. The result shows that our method is superior to the other three.

title: Cluster Queue Structure for Shared-Memory Multiprocessor Systems
abstract: Three basic structures have been proposed to organize the task queues for shared-memory multiprocessor systems: centralized, distributed, and hierarchical. Centralized structures are not suitable for massively parallel systems since the shared queue becomes a bottleneck for frequent enqueuing and dequeuing operations. Distributed structures have load imbalancing problem because of no support for workload sharing between queues. Hierarchical structures intend to combine the advantage of the previous two structures and eliminate their disadvantages. Unfortunately, we find load imbalancing still exists in the hierarchical structure, and has significant impact on system performance, particularly when the workload is heavy and irregular. After identifying the cause of this problem, we propose the use of a clustered structure in place of the hierarchical one. Analyzes and simulations show the proposed structure can provide better load balancing and less contention than the hierarchical one.

title: A bottom-up inference of loss rate
abstract: Loss tomography, as a key component of network tomography, aims to obtain the loss rate of each link in a network by end-to-end measurements. If knowing the loss model of a link, we, in fact, deal with a parametric estimate problem with incomplete data. Maximum likelihood estimates are often used in this situation to identify the unknown parameters in the loss model. Almost all methods proposed so far rely on the iterative approximation to identify the parameters that requires a long execution time. In addition, the parameters identified by those methods may not be the true values of those parameters since the iterative procedure may trap into a local maximum. In this paper, we propose an estimate that is based on the correlation between a link and its sibling brothers to identify the loss rate of the link. The proposed method, instead of using an iterative approach to approximate the maximum, employs a bottom-up approach to identify the loss rates of the links of a network. Comparing to the previous methods, the proposed method is simple and fast because it is an analytical solution.

title: Implementing parallel hmm-pfam on the EARTH multithreaded architecture
abstract: Hmmpfam is a widely used computation-intensive bioinformatics software for sequence classification. This poster describes a new parallel implementation of hmmpfam on EARTH, which is an event-driven fine-grain multithreaded programming execution model. The comparison results of the original PVM implementation and our implementation shows notable improvements on absolute speedup and scalability. On a cluster of 128 dual-CPU nodes, the execution time of a representative testbench is reduced from 15.9 hours to 4.3 minutes.

title: TiNy threads: a thread virtual machine for the Cyclops64 cellular architecture
abstract: This paper presents the design and implementation of a thread virtual machine, called TNT (or TiNy-Threads) for the IBM Cyclops64 architecture (the latest Cyclops architecture that employs a unique multiprocessor-on-a-chip design with a very large number of hardware thread units and embedded memory) - as the cornerstone of the C64 system software. We highlight how to achieve high efficiency by mapping (and matching) the TNT thread model directly to the Cyclops ISA features assisted by a native TNT thread runtime library. Major results of our experimental study demonstrate good efficiency, scalability and usability of our TNT model/implementation.

title: Toward a Software Infrastructure for the Cyclops-64 Cellular Architecture
abstract: This paper presents the initial design of the Cyclops-64 (C64) system software infrastructure and tools under development as a joint effort between IBM T.J. Watson Research Center, ETI Inc. and the University of Delaware. The C64 system is the latest version of the Cyclops cellular architecture that consists of a large number of compute nodes each employs a multiprocessor-on-a-chip architecture with 160 hardware thread units. The first version of the C64 system software has been developed and is now under evaluation. The current version of the C64 software infrastructure includes a C64 toolchain (compiler, linker, functionally accurate simulator, runtime thread library, etc.) and other tools for system control (system initialization, diagnostics and recovery, job scheduler, program launching, etc.) This paper focuses on the following aspects of the C64 system software: (1) the C64 software toolchain; (2) the C64 Thread Virtual Machine (C64 TVM) with emphasis on TiNy ThreadsTM, the implementation of the C64 TVM; (3) the system software for host control. In addition, we illustrate, through two case studies, what an application developer can expect from the C64 architecture as well as some advantages of this architecture, in particular, how it provides a cost-effective solution. A C64 chip’s performance varies across different applications from 5 to 35 times faster than common off-the-self microprocessors.

title: Exploring Financial Applications on Many-Core-on-a-Chip Architecture: A First Experiment
abstract: Computational requirements for solving models of financial derivatives, for example, the option pricing problems, are huge and demand efficient algorithms and high performance computing capabilities. This demand has been rekindled by the recent developments in the mobile technology making wireless trading a possibility. In this paper, we focus on the development of a Monte-Carlo algorithm on a modern multi-core chip architecture, Cyclops-64 (C64) under development at IBM as the experimental platform for our study in pricing options. The timing results on C64 show that various sets of simulations could be done in a real-time fashion while yielding high performance/price improvement over traditional microprocessors for finance applications.