16013631
Populating Genomes in a Dynamic Grid
We study the behavior of a spatially distributed GA (Collins and Jefferson 1991) that has several unique features. First, individuals are allowed to move within a two dimensional grid over time. Such movement results in a continual change in the local environment in which each individual interacts. Second, selection is directly based on an individual’s energy value and indirectly based on fitness. The fitness of an individual determines its initial energy level, but an individual’s energy level at any point during a run reflects a combination of its fitness and its interactions in the environment. Third, the population size can change dynamically throughout a run.
10203274
Adaptation of Length in a Nonstationary Environment
In this paper, we examine the behavior of a variable length GA in a nonstationary problem environment. Results indicate that a variable length GA is better able to adapt to changes than a fixed length GA. Closer examination of the evolutionary dynamics reveals that a variable length GA can in fact take advantage of its variable length representation to exploit good quality building blocks after a change in the problem environment.
28810285
Workflow management and resource discovery for an intelligent grid
A computational grid provides coordinated and transparent access to computing resources for grid users. Workflow management and resource discovery are two important functions of an intelligent grid. Workflow management refers to automatic workflow creation and coordinated workflow execution, and resource discovery facilitates resource allocation and claiming. In this paper we discuss workflow management and resource discovery in an intelligent grid environment.
18463797
Planning with Recursive Subgoals
In this paper, we introduce an effective strategy for subgoal division and ordering based upon recursive subgoals and combine this strategy with a genetic-based planning approach. This strategy can be applied to domains with conjunctive goals. The main idea is to recursively decompose a goal into a set of serializable subgoals and to specify a strict ordering among the subgoals. Empirical results show that the recursive subgoal strategy reduces the size of the search space and improves the quality of solutions to planning problems.
7221846
Evolving Sensor Suites for Enemy Radar Detection
Designing optimal teams of sensors to detect the enemy radars for military operations is a challenging design problem. Many applications require the need to manage sensor resources. There is a tradeoff between the need to decrease the cost and to increase the capabilities of a sensor suite. In this paper, we address this design problem using genetic algorithms. We attempt to evolve the characteristics, size, and arrangement of a team of sensors, focusing on minimizing the size of sensor suite while maximizing its detection capabilities. The genetic algorithm we have developed has produced promising results for different environmental configurations as well as varying sensor resources.
5492949
Resource Matching and a Matchmaking Service for an Intelligent Grid
We discuss the application of matching in the area of resource discovery and resource allocation in grid computing. We present a formal definition of matchmaking, overview algorithms to evaluate different matchmaking expressions, and develop a matchmaking service for an intelligent grid environment. Keywords—Grid, Matchmaking, Ontology
52804588
Cryptanalysis of the Full HAVAL with 4 and 5 Passes
HAVAL is a cryptographic hash function with variable digest size proposed by Zheng, Pieprzyk and Seberry in 1992. It has three variants, 3-, 4-, and 5-pass HAVAL. Previous results on HAVAL suggested only practical collision attacks for 3-pass HAVAL. In this paper, we present collision attacks for 4 and 5 pass HAVAL. For 4-pass HAVAL, we describe two practical attacks for finding 2-block collisions, one with 243 computations and the other with 2 36 computations. In addition, we show that collisions for 5-pass HAVAL can be found with about 2 123 computations, which is the first attack more efficient than the birthday attack.
7168030
Minimal skew clock embedding considering time variant temperature gradient
The existing temperature-aware clock embedding assumes a time-invariant temperature gradient. However, it is not solved how to find the worst-case temperature gradient leading to the worst case skew. In this paper, we develop a PErturbation based Clock Optimization(PECO) considering the time-variant temperature gradient. For a given clock topology, we minimizethe worst case skew without asking for the worst case temperature map. We decide the merging point level by level based on the sensitivity of the skew with respect to the change of merging point. Such sensitivity is calculated using a parameterized model, which is compressed by a singular-value-decomposition (SVD) and K-meansbased clustering considering the temperature correlation. The experimental results show that our algorithm reduces worst-case skew by up to 5X compared to the existing zero skew based ZST/DME method with small (up to 1%) wirelength overhead.
16750086
Supporting transactional cache consistency in mobile database systems
In a mobile computing environment, caching of frequently accessed data has been shown to be a useful technique for reducing contention on the narrow bandwidth of the wireless channels. However, the traditional client/server strategies for supporting transactional cache consistency that require extensive communications between a client and a server are not appropriate in a mobile computing environment. In this paper, we propose a new protocol, called OCC-UTS (Optimisitic Concurrency Control with Update TimeStamp), to support transactional cache consistency in a wireless mobile computing environment by utilizing the broadcast-based solutions for the problem of invalidating caches. The consistency check on accessed data and the commitment protocol are implemented in a truly distributed fashion as an integral part of cache invalidation process, with most burden of consistency check being downloaded to mobile clients. Also, our esperiments based on an analytical model substantiate the basic idea and study the performance characteristics. Experimental results show that OCC-UTS protocol without local cache outperforms other competitor protocol, and the more frequent a mobile client accesses data items the more efficient OCC-UTS protocol with local cache is. With respect to disconnection, a mobile client aborts its transaction if it disconnects more than the invalidation broadcast window size. Thus, the tolerance to disconnection is improved if the invalidation broadcast window size is extended.
11499161
Minimal replication cost for availability
Today, the utility of many replicated Internet services is limited by availability rather than raw performance. To better understand the effects of replica placement on availability, we propose the problem of minimal replication cost for availability. Let replication cost be the cost associated with replica deployment, dynamic replica creation and teardown at n candidate locations. Given client access patterns, replica failure patterns, network partition patterns, a required consistency level and a target level of availability, the minimal replication cost is the lower bound on a system's replication cost. Solving this problem also answers the dual question of optimal availability given a constraint on replication cost.We design the first algorithm we are aware of to solve the problem, through reduction to integer linear programming and enumeration of pruned serialization orders. Using practical faultloads and workloads, we demonstrate that the exponential complexity of our algorithm is tractable for practical problems with hundreds of candidate locations. The lower bound computed by our algorithm is tight, but the tightness can be sacrificed by a proposed optimization for large problems. We also show that with low replica creation and teardown costs, the bound is close to tight in practical problems even with the optimization.
120152362
Graph matching using spectral embedding and alignment
This paper describes how graph-spectral methods can be used to transform the node correspondence problem into one of point-set alignment. We commence by using the ISOMAP algorithm to embed the nodes of a graph in a low-dimensional Euclidean space. With the nodes in the graph transformed to points in a metric space, we can recast the problem of graph matching into that of aligning the points. Here, we use a variant of the Scott and Longuet-Higgins algorithm to find point correspondences. We experiment with the resulting algorithm on a number of real-world problems.