Diversification and Intensification in Parallel {SAT} Solving

International audienceIn this paper, we explore the two well-known principles of diversification and intensification in portfolio-based parallel SAT solving. These dual concepts play an important role in several search algorithms including local search, and appear to be a key point in modern parallel SAT solvers. To study their trade-off, we define two roles for the computational units. Some of them classified as Masters perform an original search strategy, ensuring diversification. The remaining units, classified as Slaves are there to intensify their master's strategy. Several important questions have to be answered. The first one is what information should be given to a slave in order to intensify a given search effort? The second one is, how often, a subordinated unit has to receive such information? Finally, the question of finding the number of subordinated units along their connections with the search efforts has to be answered. Our results lead to an original intensification strategy which outperforms the best parallel SAT solver, and solves some open SAT instances

Validation, Verification And Integrity Issues In Expert And Database Systems

In August 1998 an international workshop on validation, verification and integrity issues of expert and database systems was held in Vienna in conjunction with the Ninth Conference on Database and Expert Systems Applications (DEXA'98). This paper reports on the results of this workshop and summarises the issues identified for future research in this area. Details of the presented papers and some additional information can be found at the workshop WWW site http://www.csc.liv.ac.uk/¸frans/ dexaWorkshop.html. 1 INTRODUCTION Validation, verification and integrity (VV&I) respectively concern the truthfulness of a system with respect to its problem domain, the correctness of its construction, and maintaining the validity of the evolving system throughout its life. This distinction, akin to the differences in traditional software engineering, between these three terms is neatly captured in Bohem's definitions of validation and verification [Bohem 81] and the additional definition of integrit..

The psychological process of travel destination choice

This paper reviews literature on travel destination choice and organizes these studies systematically. A “cell–system” structure is proposed to describe the psychological process of travel destination choice. When forming decisions on vacations, tourists gather information on potential destinations and evaluate visit intentions among potential destinations (“cell”). The visit intentions are successively compared while information is updated in the process (“system”). The “cell–system” structure provides a clear view of the psychological process of travel destination choice. Empirical studies based on the structure can provide further insights into why and how tourists choose travel destinations

A stochastic multidimensional unfolding approach for representing phased decision outcomes

consumer psychology, multidimensional scaling, maximum likelihood, consideration sets, multidimensional unfolding, successive categories analysis,