468988
Volunteer availability based fault tolerant scheduling mechanism in desktop grid computing environment
Fault tolerance is essential to the further development of desktop grid computing system in order to guarantee continuous and reliable execution of tasks in spite of failures. In a desktop grid computing environment, volunteers are often susceptible to volunteer autonomy failures such as volatility failure and interference failure in the middle of execution of tasks because a desktop grid computing maximally respects autonomy of volunteers. The failures result in an independent livelock problem (i.e. the delay and blocking of the entire execution of a job). Therefore, the failures should be considered in a scheduling mechanism. In This work, in order to tolerate volunteer autonomy failures, we propose a new fault tolerant scheduling mechanism. First, we specify a volunteer autonomy failures and an independent livelock problem. Then, we propose a volunteer availability which reflects the degree of volunteer autonomy failures. Finally, we propose a fault tolerant scheduling mechanism based on volunteer availability (which is called VAFTSM).
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.
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.
10832557
Adaptive group scheduling mechanism using mobile agents in peer-to-peer grid computing environment
Peer-to-peer grid computing is an attractive computing paradigm for high throughput applications. However, both volatility due to the autonomy of volunteers (i.e., resource providers) and the heterogeneous properties of volunteers are challenging problems in the scheduling procedure. Therefore, it is necessary to develop a scheduling mechanism that adapts to a dynamic peer-to-peer grid computing environment. In this paper, we propose a Mobile Agent based Adaptive Group Scheduling Mechanism (MAAGSM). The MAAGSM classifies and constructs volunteer groups to perform a scheduling mechanism according to the properties of volunteers such as volunteer autonomy failures, volunteer availability, and volunteering service time. In addition, the MAAGSM exploits a mobile agent technology to adaptively conduct various scheduling, fault tolerance, and replication algorithms suitable for each volunteer group. Furthermore, we demonstrate that the MAAGSM improves performance by evaluating the scheduling mechanism in Korea@Home.
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
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
6005789
Optimizing SMT Processors for High Single-Thread Performance
Simultaneous Multithreading (SMT) processors achieve high processor throughput at the expense of single-thread performance. This paper investigates resource allocation policies for SMT processors that preserve, as much as possible, the single-thread performance of designated “foreground” threads, while still permitting other “background” threads to share resources. Since background threads o ns uch an SMT machine have an ear-zero performance impact on foreground threads, we refer to the background threads as transparent threads. Transparent threads are ideal for performing low-priority or non-critical computations, with applications in process scheduling, subordinate multithreading, and on-line performance monitoring. To realize transparent threads, we propose three mechanisms for maintaining the transparency of background threads: slot prioritization, background thread instruction-window partitioning, and background thread flushing. In addition, we propose three mechanisms to boost background thread performance without sacrificing transparency: aggressive fetch partitioning, foreground thread instruction-window partitioning, and foreground thread flushing. We implement our mechanisms on a detailed simulator of an SMT processor, and evaluate them using 8 benchmarks, including 7 from the SPEC CPU2000 suite. Our results show when cache and branch predictor interference are factored out, background threads introduce less than 1% performance degradation on the foreground thread. Furthermore, maintaining the transparency of background threads reduces their throughput by only 23% relative to an equal priority scheme. To demonstrate the usefulness of transparent threads, we study Transparent Software Prefetching (TSP), an implementation of software data prefetching using transparent threads. Due to its near-zero overhead, TSP enables prefetch instrumentation for all loads in a program, eliminating the need for profiling. TSP, without any profile information, achieves a 9.41% gain across 6 SPEC benchmarks, whereas conventional software prefetching guided by cache-miss profiles increases performance by only 2.47%.
3185620
A simple algorithm for homeomorphic surface reconstruction
Abstract 1 Introduction The problem of computing a piecewise linear approximation to a surface from a set of sam- ple points on the surface has been a focus of research in solid modeling and graphics due to its many applications. The input to this sur- face reconstruction problem consists of the three dimensional coordinates of the sampled points. The crust algorithm of [1] reconstructs a surface with topological and geometric guarantees using the Voronoi diagram of the input point set. We present new observations that simplify both the algorithm and the proofs for the crust, and we give for the first time a proof that the crust is homeomorphic to the input surface. *Dept. of Computer Science, U. of Texas, Austin TX 78712. e-mail: amenta@cs.utexas.edu tDept, of Computer Science, U. of Texas, Austin, TX 78712. e-mail: sunghee@cs.utexas.edu SDept. of Computer and Information Science, Ohio State U., Columbus, OH 43210. e-mail: t amaldey¢ci s. ohio-state, edu §Dept. of Computer and Information Science, Ohio State U., Columbus, OH 43210. e-mail: leekha@cis, ohio-state, edu
5975093
Multi-chain prefetching: effective exploitation of inter-chain memory parallelism for pointer-chasing codes
Presents multi-chain prefetching, a technique that utilizes offline analysis and a hardware prefetch engine to prefetch multiple independent pointer chains simultaneously, thus exploiting inter-chain memory parallelism for the purpose of memory latency tolerance. This paper makes three contributions. First, we introduce a scheduling algorithm that identifies independent pointer chains in pointer-chasing codes and computes a prefetch schedule that overlaps serialized cache misses across separate chains. Our analysis focuses an static traversals. We also propose using speculation to identify independent pointer chains in dynamic traversals. Second, we present the design of a prefetch engine that traverses pointer-based data structures and overlaps multiple pointer chains according to our scheduling algorithm. Finally, we conduct an experimental evaluation of multi-chain prefetching and compare its performance against two existing techniques: jump pointer prefetching and prefetch arrays. Our results show that multi-chain prefetching improves the execution time by 40% across six pointer-chasing kernels from the Olden benchmark suite and by 8% across four SPECInt CPU2000 benchmarks. Multi-chain prefetching also outperforms jump pointer prefetching and prefetch arrays by 28% on Olden, and by 12% on SPECInt. Furthermore, speculation can enable multi-chain prefetching for some dynamic traversal codes, but our technique loses its effectiveness when the pointer-chain traversal order is unpredictable. Finally, we also show that combining multi-chain prefetching with prefetch arrays can potentially provide higher performance than either technique alone.
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.
14566323
Semantic Selection for Resolution in Clause Graphs
In this contribution we present a variant of a resolution theorem prover which selects resolution steps based on the proportion of models a newly generated clause satisfies compared to all models given in a reference class. This reference class is generated from a subset of the initial clause set. Since the empty clause does not satisfy any models, preference is given to such clauses which satisfy few models only. Because computing the number of models is computationally expensive on the one hand, but will remain almost unchanged after the application of one single resolution step on the other hand, we adapt Kowalski's connection graph method to store the number of models at each link.