9574067
The Hierarchical Fair Competition (HFC) Framework for Sustainable Evolutionary Algorithms
Many current Evolutionary Algorithms (EAs) suffer from a tendency to converge prematurely or stagnate without progress for complex problems. This may be due to the loss of or failure to discover certain valuable genetic material or the loss of the capability to discover new genetic material before convergence has limited the algorithm's ability to search widely. In this paper, the Hierarchical Fair Competition (HFC) model, including several variants, is proposed as a generic framework for sustainable evolutionary search by transforming the convergent nature of the current EA framework into a non-convergent search process. That is, the structure of HFC does not allow the convergence of the population to the vicinity of any set of optimal or locally optimal solutions. The sustainable search capability of HFC is achieved by ensuring a continuous supply and the incorporation of genetic material in a hierarchical manner, and by culturing and maintaining, but continually renewing, populations of individuals of intermediate fitness levels. HFC employs an assembly-line structure in which subpopulations are hierarchically organized into different fitness levels, reducing the selection pressure within each subpopulation while maintaining the global selection pressure to help ensure the exploitation of the good genetic material found. Three EAs based on the HFC principle are tested - two on the even-10-parity genetic programming benchmark problem and a real-world analog circuit synthesis problem, and another on the HIFF genetic algorithm (GA) benchmark problem. The significant gain in robustness, scalability and efficiency by HFC, with little additional computing effort, and its tolerance of small population sizes, demonstrates its effectiveness on these problems and shows promise of its potential for improving other existing EAs for difficult problems. A paradigm shift from that of most EAs is proposed: rather than trying to escape from local optima or delay convergence at a local optimum, HFC allows the emergence of new optima continually in a bottom-up manner, maintaining low local selection pressure at all fitness levels, while fostering exploitation of high-fitness individuals through promotion to higher levels.
19842410
Automated design approaches for multi-domain dynamic systems using bond graphs and genetic programming
13136257
An agent-based architecture for distributed interfaces and timed media in a storytelling application
This paper presents an agent-based architecture that enables the presentation of interactive timed media to distributed and networked devices. The architecture provides an automatic mapping of the same document to different environments. It uses a hierarchy of PAC (Presentation-Abstraction-Control) agents, which allows separating the presentation aspects from the control aspects and dynamically registering the new PAC agents to the system.
4103897
Component-wise mapping of media-needs to a distributed presentation environment
Whereas formal specification and verification have shown value by improving reliability and trustworthiness of traditional industrial systems, we made a contribution by applying them to the field of distributed multimedia presentations in an ambient intelligence context. We investigate a mapping problem in which media needs are to be satisfied using given presentation resources. The goal of the investigation is to see whether Broy's stream-based component framework can be used to model media-related interfaces and constraints in an elegant way. The formalization will serve as a framework for the development of an automated mapper that can handle real media needs and real presentation resources. It combines the well-known notations of Z with an underlying concurrency theory. We show that not only verification issues can be handled such as bandwidth and delay constraints, but also architecture-level issues such as network structural media-type compatibilities
6565484
A timing-constrained simultaneous global routing algorithm
Proposed in this paper is a new approach for VLSI interconnect global routing that can optimize both congestion and delay, which are often competing objectives. The authors' approach provides a general framework that may use any single-net routing algorithm and any delay model in global routing. It is based on the observation that there are several routing topology flexibilities that can be exploited for congestion reduction under timing constraints. These flexibilities are expressed through the concepts of a soft edge and a slideable Steiner node. Starting with an initial solution where timing-driven routing is performed on each net without regard to congestion constraints, this algorithm hierarchically bisects a routing region and assigns soft edges to the cell boundaries along the bisector line. The assignment is achieved through a network flow formulation so that the amount of timing slack used to reduce congestions; is adaptive to the congestion distributions. Finally, a timing-constrained rip-up-and-reroute process is performed to alleviate the residual congestions. Experimental results on benchmark circuits are quite promising and the run time is between 0.02 s and 0.15 s per two-pin net.
10406726
Associative Skew Clock Routing for Difficult Instances
In clock network synthesis, sometimes skew constraints are required only within certain groups of clock sinks and do not exist between different groups. This is the so-called associative skew clock routing problem. Although the number of constraints is reduced, the problem becomes more difficult to solve due to the enlarged solution space. The perhaps only previous work used a very primitive delay model and cannot handle difficult instances in which sink groups are intermingled. We reuse existing techniques to solve this problem, including the difficult instances, based on a more accurate and popular delay model. Experimental results show that our algorithm can reduce the total clock routing wirelength by 12% on average compared to greedy-DME which is one of the best zero skew routing algorithms
41764873
Supporting provision and access of educational visual resources on the web