4770738
Parallel Simulated Annealing using Speculative Computation
A parallel simulated annealing algorithm that is problem-independent, maintains the serial decision sequence, and obtains speedup which can exceed log/sub 2/P on P processors is discussed. The algorithm achieves parallelism by using the concurrency technique of speculative computation. Implementation of the parallel algorithm on a hypercube multiprocessor and application to a task assignment problem are described. The simulated annealing solutions are shown to be, on average, 28% better than the solutions produced by a random task assignment algorithm and 2% better than the solutions produced by a heuristic. >
18137632
Collecting Data About Logic Simulation
Design of high-performance hardware and software-based gate-switch-level logic simulators requires knowledge about the logic simulation process itself. Unfortunately, little data is publicly available concerning key aspects of this process. An example of this is the lack of published empirical measurements relating to the time distribution of events generated by such simulators. This paper presents a gate-switch-level logic simulator lsim which is oriented towards the collection of data about the simulation process. The basic components of lsim are reviewed, and its relevant data gathering facilities are discussed. An example is presented which illustrates the use of lsim in gathering data on event distributions and on communications requirements under alternative logic circuit partitionings.
5272318
On Designing Interconnection Networks for Multiprocessors
This paper considers various physical constraints which influence the design of interconnection networks used in multiprocessor systems. Design expressions are presented for implementing an N log N packet passing interconnection network composed for circuit switched crossbar chip modules. Expressions reflecting chip level and board level pin and area constraints are derived and used to determine the network delay expected at a given clock frequency. Logic and memory delay, signal path delay, clock skew and clock tree delay parameters are defined and used to determine the maximum frequency which can be obtained with a given design. An example 2048x2048 network... Read complete abstract on page 2.
206622431
Pin Limitations and Partitioning of VLSI Interconnection Networks
Multiple processor interconnection networks can be characterized as having N' inputs and N' outputs, each being B' bits wide. A major implementation constraint of large networks in the VLSI environment is the number of pins available on a chip, Np. Construction of large networks requires partitioning of the N' * N' * B' network into a collection of N * N switch modules with each input and output port being B (B ≤ B') bits wide. If each module corresponds to a single chip, then a large network can be implemented by interconnecting the chips in a particular manner. This correspondence presents a methodology for selecting the optimum values of N and B given values of N', B', Np, and the number of control lines per port. Models for both banyan and crossbar networks are developed and arrangements yielding minimum: 1) number of chips, 2) average delay through the network, and 3) product of number of chips and delay, are presented.
27473158
Interconnection Networks: Physical Design and Performance Analysis
This paper considers various physical constraints which influence the design of interconnection networks used in multiprocessor systems. Design expressions are presented for implementing an N log N packet passing interconnection network composed of circuit switched crossbar chip modules. Expressions reflecting chip level and board level pin and area constraints are derived and used to determine the network delay expected at a given clock frequency. Logic and memory delay, signal path delay, clock skew, and clock distribution delay parameters are defined and used to determine the maximum frequency which can be obtained with a given design. An example 2048 × 2048 network design is considered. This example indicates that using aggressive packaging and MOS technology, a clock frequency of about 40 Mhz is achievable. However, even at this frequency, this network would result in a one-way delay (ignoring blocking and hot spot delays) of about 1 μsec. A read operation from memory requiring a round trip would thus require about 2 μsec. This represents considerable slowdown when compared with accessing strictly local memory and appears to be a major problem in the design of network centered multiprocessor architectures.
34325813
Timing Control of VLSI Based NlogN and Crossbar Networks
Two basic data flow control methods for circuit switched, pipelined networks of the general nlogn and crossbar (cb) topologies are modelled and their effects on overall data rates achievable are determined. The synchronous method uses a global clock and as network modules grow, clock skew and clock tree charge/discharge times grow resulting in lower data rates. The asynchronous method relies on local request/acknowledge signals to control data movement and hence its performance is less affected by system growth. 12 references.
10278200
Efficient Incremental Garbage Collection for Client-Server Object Database Systems
We briefly outline the main characteristics of an efficient server-based algorithm for garbage collecting object-oriented databases in a client-server environment. The algorithm is incremental and runs concurrently with client transactions. Unlike previous algorithms, it does not hold any locks on data and does not require callbacks to clients. It is fault tolerant, but performs very little logging. The algorithm has been designed to be integrated into existing OODB systems, and therefore it works with standard implementation techniques such as two-phase locking and write-ahead-logging. In addition, it supports client-server performance optimizations such as client caching and flexible management of client buffers. The algorithm has been implemented in the EXODUS storage manager before being evaluated.
59766135
Improving Responsiveness for Wide-Area Data Access
Improving Resp onsiveness for WideArea Data AccessLaurent AmsalegPhilipp e BonnetMichael J FranklinINRIABullUniversity of MarylandAnthonyTomasicTolga UrhanINRIAUniversity of MarylandAbstractIn a widearea environment the time rquird to obtain data from remote sources can varyunpredictably due to network congestion link failure or other problems Traditional techniquesfor query optimization and query execution do not cope wel l with such unpredictabilityThestatic nature of those techniques prevents them from adapting to remote access delays that ariseat runtime In this paper we describe two separate but relatedtechniques aimed at tackling thisproblem The rst technique cal led Query Scrambling hides relatively short intermittent delaysby dynamical ly adjusting query execution plans onthey The second technique addresses thelongerterm unavailability of data sources by al lowing the return of partial query answers whensome of the data needed to ful ly answer a query are missingIntro ductionThe continued dramatic growth in global interconnectivity via the Internet has made aroundtheclo ckondemand access to widelydistribu ted data a common exp ectation for many computer users Advances in resource discoery heterogeneous data management and semistructured data managementare providingsemanticto ols to enable the access and correlation of data from diverse widelydistributedsources A limiting factor of suchwork however is the diculty of providing resp onsive data access tousers due to the highly varying resp onsetime and availabilitycharacteristics of remote data sources ina widearea environment Data access over widearea networks inolves a large numb er of data sourcesintermediate sites and communications links all of which are vulnerable to congestion and failuresSuch problems can intro duce signicant and unpredictabledelaysin the access of information fromremote sourcesCurrent distributed query pro cessing approaches p erform p o orly in the widearea environmentThey p ermit unexp ected delays to directly increase the query resp onse time allowing query executionCopyright IEEE Personal use of this material is permitted However permission to reprintrepublish this material for advertising or promotional purposes or for creating new col lective works for resale or rdistribution to serversor lists or to reuse any copyrightedcomponent of this work in other works must be obtainedfrom the IEEEBulletin of the IEEE Computer So cietyTechnical Committee on Data EngineeringThis work was partially supp orted by the NSF under Grant IRI by Bellcore and by an IBM SharedUniversity Researchaward Laurent Amsaleg did this work while he was at the Univy of Maryland and was supp ortedin part by an INRIA Fellowship Philipp e Bonnet and AnthonyTomasic p erformed this work in the context of Dyadean RD jointventure b etween Bull and INRIA
15962925
Garbage collection for a client-server persistent object store
We describe an efficient server-based algorithm for garbage collecting persistent object stores in a client-server environmnet. The algorithm is incremental and runs concurrently with client transactions. Unlike previous algorithms, it does not hold any transactional locks on data and does non require callbacks to clients. It is fault-tolerant, but performs very little logging. The algorithm has been designed to be integrated into existing systems, and therefore it works with standard implementation techniques such as Two-Phase Locking and Write-Ahead-Logging. In addition, it supports client-server performance optimizations such as client caching and flexible management of client buffers. We describe an implementation of the algorithm in the EXODUS storage manager and present the results of a performance study of the implementation.
5720179
Enhancing privacy and trust in electronic communities
A major impediment to using recommendation systems and collective knowledge for electronic commerce is the reluctance of individuals to reveal preferences in order to find groups of people that share them. An equally important barrier to fluid electronic commerce is the lack of agreed upon trusted third parties. We propose new non-third party mechanisms to overcome these barriers. Our solutions facilitate finding shared preferences, discovering communities with shared values, removing disincentives posed by liabilities, and negotiating on behalf of a group. We adapt known techniques from the cryptographic literature to enable these new capabilities.
6459671
Extensible data management in the middle-tier
Current data management solutions are optimized for intra-enterprise, client-server applications. They depend on predictability, predefined structure and universal administrative control, and cannot easily cope with change and lack of structure. However, modern e-commerce applications are dynamic, unpredictable, organic, and decentralized, and require adaptability. eXtensible Data Management (XDM) is a new approach that enables rapid development and deployment of networked, data-intensive services by providing semantically-rich, high-performance middle-tier data management, and allows heterogeneous data from different sources to be accessed in a uniform manner. We discuss how middle tier extensible data management can benefit an enterprise, and present technical details and examples from the Index Fabric, an XDM engine we have implemented.