26521398
Advanced Stochastic Host State Modeling to Reliable Computation in Global Computing Environment
To design a stable global computing environment supporting reliable job execution and covering unanticipated state changes of hosts, the dynamic characteristics (i.e. volatilities) of hosts should be considered. Since a host is not dedicated to the system, voluntary hosts are free to leave and join autonomously in the middle of execution. As current systems do not relate volatility to a scheduling procedure, global computing systems suffer from performance degradation, reliability loss, job interruption, and execution time delays. For dependable computation, we propose Advanced Stochastic Host State Modeling (ASHSM), which is based on Markov model relating to execution availability quantifying duration and regularity of execution patterns of each host. Through the model, the system predicts desktop activities and allocates jobs according to the host features. Furthermore ASHSM alleviates unreliability due to unstable resource provision and job suspension during execution
16177959
Multi-Node Global Directory Construction in Peer-to-Peer Systems
In P2P systems, the speed of searching for desired lists of sharable files is one of the most important measurement issues in evaluation of overall system performance. Although the searching schemes of existing non-structured P2P systems have been improved to enhance speed considerably, they still never reach to the level of those of the centralized and structured systems. In this paper, we propose a multi-node global directory in P2P systems, where all the lists of sharable resources of the joining peers are aggregated and divided into the chosen nodes while keeping collating sequence as a whole to make one big linked list. Thus in indexed sequential searching, the system provides us with convenience of using the command like 'dir' of MS-DOS, and in general keyword searching, which is naturally impossible for the structured P2P systems, the searching speed is even faster than those of centralized P2P systems since a small list segment is scanned at each node synchronously in parallel
14154834
Region-based stage construction protocol for fault tolerant execution of mobile agent
Fault tolerance is essential to the development of reliable mobile agent systems in order to guarantee continuous execution of mobile agents. For this purpose, previous work has proposed fault tolerant protocols for mobile agent execution based on stage construction. However, when previous protocols are applied to a multiregion mobile agent computing environment, the overhead of work such as monitoring, election, voting and agreement is increased. We propose a region-based stage construction (RBSC) protocol for fault tolerant execution of mobile agents in a multiregion mobile agent computing environment. The RBSC protocol uses new concepts of quasiparticipant and substage in order to put together some places located in different regions within a stage in the same region. Therefore, the RBSC protocol decreases the overhead of stage works. Consequently, the RBSC protocol decreases the total execution time of mobile agents.
17124028
Probabilistic Observation Prediction Model based E4 Scheduling Mechanism in Peer to Peer Grid Computing
Peer to peer (P2P) grid computing is an Internet-based parallel computing paradigm to achieve tremendous computing power by voluntary peers. Since peers are not dedicated to a system, peers are free to leave and join autonomously during computation in this computing environment. A scheduling mechanism must cover the volatility of peers to support a reliable P2P grid computing system. Most existing P2P grid computing systems, however, suffer from blocked job execution and delayed makespan because they do not consider the volatile features of peers in the scheduling procedure. In order to improve system reliability, we propose a probabilistic observation prediction (POP) -based EA scheduling mechanism supporting three advanced scheduling policies: loose time constraint policy (LTCP), strict time constraint policy (STCP), and hybrid time constraint policy (HTCP). LTCP is for general use, STCP aims at minimizing makespan, and HTCP attempts to improve efficiency, and performance-to-cost ratio. All policies are based on stochastic modeling of peer state transition while endeavoring to manage the volatile features of peers
41968338
Group-Based Scheduling Scheme for Result Checking in Global Computing Systems
This paper considers the problem of correctness to fault-tolerance in global computing systems. Global computing system has been shown to be exposed to intentional attacks, where authentication is not relevant, network security techniques are insufficient. To guarantee correctness for computation, fault-tolerance schemes have been used to majority voting and spot-checking but these schemes intend to high computation delay because are not applied scheduling scheme for result checking. In this paper, we propose a new technique called GBSS(Group-Based Scheduling Scheme) which guarantee correctness and reduce computation delay by using fault-tolerant scheduling scheme to the result checking. Additionally, simulation results show increased usable rate of the CPU and increased performance of the system.
34200542
MJSA: Markov job scheduler based on availability in desktop grid computing environment
In a desktop grid computing environment, voluntary desktops (i.e., resource providers) are free to leave and join independently in the middle of execution. To develop a reliable desktop grid computing system, a scheduling scheme must consider the dynamic nature (i.e., volatility) of volunteers. Existing desktop grid computing systems, however, do not consider volatility in their scheduling procedures. As a result, job execution is often suspended, resulting in delayed completion time and degraded performance and reliability. To solve these limitations, we propose the Markov Job Scheduler based on Availability (MJSA) supporting three advanced scheduling schemes: OPTIMIST, PESSIMIST, and REALIST. These scheduling schemes are based on stochastic modeling of desktop availability. In the OPTIMIST scheme, in which time constraints are relaxed, the MJSA provides reliable resource selection at low cost. In the PESSIMIST scheme, where time constraints are rigid, the MJSA enables stable makespan in strictly time. Finally, in the REALIST scheme, where time constraints are only partially relaxed, the MJSA provides enhanced cost efficiency. In conclusion, the MJSA improves performance and reliability by adapting the appropriate scheduling scheme when selecting volunteers according to the needs of applications.
19996434
A multi-material virtual prototyping system
Abstract This paper proposes a multi-material virtual prototyping system for digital fabrication of heterogeneous prototypes. It consists mainly of a topological hierarchy-sorting algorithm for processing slice contours, and a virtual simulation system for visualisation and optimisation of multi-material layered manufacturing (MMLM) processes. The topological hierarchy-sorting algorithm processes the hierarchy relationship of complex slice contours. It builds a parent-and-child list that defines the containment relationship of the slice contours, and subsequently arranges the contours in an appropriate sequence, which facilitates toolpath planning for MMLM by avoiding redundant tool movements. The virtual simulation system simulates MMLM processes and provides stereoscopic visualisation of the resulting multi-material prototypes for quality analysis and optimisation of the processes.
1958153
Maintaining Consistency Under Isolation Relaxation of Web Services Transactions
For efficiently managing Web Services (WS) transactions which are executed across multiple loosely-coupled autonomous organizations, isolation is commonly relaxed. A Web services operation of a transaction releases locks on its resources once its jobs are completed without waiting for the completions of other operations. However, those early unlocked resources can be seen by other transactions, which can spoil data integrity and causes incorrect outcomes. Existing WS transaction standards do not consider this problem. In this paper, we propose a mechanism to ensure the consistent executions of isolation-relaxing WS transactions. The mechanism effectively detects inconsistent states of transactions with a notion of a completion dependency and recovers them to consistent states. We also propose a new Web services Transaction Dependency management Protocol (WTDP). WTDP helps organizations manage the WS transactions easily without data inconsistency. WTDP is designed to be compliant with a representative WS transaction standard, the Web Services Transactions specifications, for easy integration into existing WS transaction systems. We prototyped a WTDP-based WS transaction management system to validate our protocol.
19983253
A selective DVS technique based on battery residual
Abstract Conventional research on DVS assumes that the battery, which is the power source of most mobile devices, provides constant power; the battery, however, has unique discharge characteristics due to its chemical properties. Based on the residual characteristics of the battery, this paper presents a practical approach towards a battery-aware DVS mechanism that can easily be applied to conventional operating systems. The proposed policy monitors the battery residual in runtime, classifies the current battery state as one of three—the recovery effect region, the rate capacity region and the alarm region—then applies a suitable DVS algorithm according to each region, which takes advantage of the underlying battery characteristics. Experiments on commercial PDAs (iPAQ5550 and Zaurus SL-860 PDA) running MPEG applications showed that our policy significantly extends the battery lifetime, compared to the conventional DVS method, with only a marginal QoS degradation.
6394953
Accelerating Database Processing at e-Commerce Sites
Most e-commerce Web sites dynamically generate their contents through a three-tier server architecture composed of a Web server, an application server, and a database server. In such an architecture, the database server easily becomes a bottleneck to the overall performance. In this paper, we propose WDBAccel, a high-performance database server accelerator that significantly improves the throughput of the database processing, and thus that of the overall Web site. WDBAccel eliminates costly, complex query processing needed to obtain query results by reusing previous query results for subsequent queries. This differentiates WDBAccel from other database cache systems, which replicate a database into multiple conventional DBMS’s and distribute queries among them. We evaluate the performance of WDBAccel by using the queries of the TPC-W benchmark. The measurement results show that WDBAccel outperforms DBMS-based cache systems by up to an order of magnitude.
858957
Hidden-Mode Markov Decision Processes for Nonstationary Sequential Decision Making
Problem formulation is often an important first step for solving a problem effectively. In sequential decision problems, Markov decision process (MDP) ([2]; [22]) is a model formulation that has been commonly used, due to its generality, flexibility, and applicability to a wide range of problems. Despite these advantages, there are three necessary conditions that must be satisfied before the MDP model can be applied; that is, 
 
1. 
 
The environment model is given in advance (a completely-known environment). 
 
 
 
 
2. 
 
The environment states are completely observable (fully-observable states, implying a Markovian environment). 
 
 
 
 
3. 
 
The environment parameters do not change over time (a stationary environment).