43108075
Bottom Up Algorithm to Identify Link-Level Transition Probability
Network tomography aims to obtain network characteristics by end-to-end measurements. Most works carried out in the past focused on the methods and methodologies to identify some of the characteristics, such as loss rate, delay distribution, etc. which are typical static statistical variables showing long-term network behaviors. In contrast to the previous works, we in this paper turn our attention to dynamic characteristics, e.g. transition probability of each link, which unveil the temporal correlation of traffic flows. Those dynamic characteristics could be more important than those static ones since the temporal information can be used in prediction. Apart from that, those characteristics are essential to many other issues, including the models used in network tomography. To identify transition probabilities by end-to-end measurements and in a real-time manner is a challenging task although the problem can be formulated by a hidden Markov model (HMM). Instead of using Baum-Welch algorithm to identify the transition probabilities because it needs a long execution time, we propose a new method that consider the correlations observed by receivers to obtain the transition probabilities in a simple and real-time manner. The proposed method is equal to a closed form solution that makes it a candidate for real-time network control.
44553256
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.
25408259
Cluster Queue Structure for Shared-Memory Multiprocessor Systems
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.
2727213
Queue structures for shared-memory multiprocessor systems
Three basic structures have been proposed to organize the task queues for shared-memory multiprocessor systems: centralized, distributed, and hierarchical structures. The hierarchical structure intends to combine the advantage of the other two structures and eliminate their disadvantages. Unfortunately, we find it still has serious load imbalancing, in particular when the workload is heavy and irregular. We propose the use of a forest structure in place of a hierarchical one. Simulation shows the proposed structure can provide better load balancing and less contention than the hierarchical one.
7778914
Implementation of process migration in Amoeba
The design of a process migration mechanism for the Amoeba distributed operating system is described. The primary motivation for this implementation is to carry out experimental and realistic studies of load balancing algorithms for a distributed operating system. Our aim has been the implementation of a mechanism which is general, efficient and fully transparent and which is reliable in the presence of network and processor failures.<<ETX>>
11673960
Implementing parallel hmm-pfam on the EARTH multithreaded architecture
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.
1403657
TiNy threads: a thread virtual machine for the Cyclops64 cellular architecture
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.
17223697
Sequential Consistency Revisit: The Sufficient Condition and Method to Reason the Consistency Model of a Multiprocessor-on-a-Chip Architecture
In his seminal paper in 1979 [1] on memory consistency, Lamport proposed two requirements for a multiprocessor system to be sequentially consistent. The second condition stated that memory “requests from all processors issued to an individual memory module are serviced from a single FIFO queue. Issuing a memory request consists of entering the request on this queue”. Recently, the authors have the opportunity to revisit Lamport’s conditions in the context of a design study of the IBM Cyclops multiprocessoron-a-chip architecture (known as BG/C) from the system software angle. We find that when a multiprocessor system employs a network to communicate with its shared memory modules – such as in the BG/C architecture we need to carefully elaborate Lamport’s requirements to cover the network. Thus we have refined the Lamport’s second requirement along this line and demonstrated that the revised conditions are sufficient for ensuring the sequentially consistent behaviors for a class of BG/C-like architectures.
6376339
Exploring Financial Applications on Many-Core-on-a-Chip Architecture: A First Experiment
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.