On Improving Local Search for Unsatisfiability

Stochastic local search (SLS) has been an active field of research in the last few years, with new techniques and procedures being developed at an astonishing rate. SLS has been traditionally associated with satisfiability solving, that is, finding a solution for a given problem instance, as its intrinsic nature does not address unsatisfiable problems. Unsatisfiable instances were therefore commonly solved using backtrack search solvers. For this reason, in the late 90s Selman, Kautz and McAllester proposed a challenge to use local search instead to prove unsatisfiability. More recently, two SLS solvers - Ranger and Gunsat - have been developed, which are able to prove unsatisfiability albeit being SLS solvers. In this paper, we first compare Ranger with Gunsat and then propose to improve Ranger performance using some of Gunsat's techniques, namely unit propagation look-ahead and extended resolution

Relevance of Social, Economic, and Environmental Impacts on Residents’ Satisfaction with the Public Administration of Tourism

Those in charge of tourism destinations face the need to create tourism development models compatible with the essence of the localities that they manage. These models have to be sustainable, both environmentally and socially, and also must become drivers of the local economy. However, tourists also generate negative impacts in the locality which, when they are perceived by the residents, can give rise to a rejection of visitors. Hence, improving the tourism management is necessary. This is why to know the residents’ perceptions about the impacts of tourism is essential. Moreover, measuring the impact effects on their satisfaction with the public administration of the destination can be of great usefulness. This study falls into this research line, as it proposes a model to measure these impacts and their effect on satisfaction. To do so, an empirical study is performed among residents in the city of Seville (southern Spain, one of the most visited destinations in the world), based on subjective economic, social, and environmental indicators. The results show that the citizens value three types of impacts, the social impact coming after the economic impact as to its influence on their satisfaction with the administration. Based on this, we postulate that the efforts made to attract events to the city, or to improve connections to access a broader market, must be approached as public procurements in which selection criteria that are compatible with the destination’s positioning and strategy prevail. Social and environmental criteria should be considered among these criteria