On Applying Unit Propagation-Based Lower Bounds in Pseudo-Boolean Optimization

Unit propagation-based (UP) lower bounds are used in the vast majority of current Max-SAT solvers. However, lower bounds based on UP have seldom been applied in Pseudo-Boolean Optimization (PBO) algorithms derived from the DPLL procedure for Propositional Satisfiability (SAT). This paper enhances a DPLL-style PBO algorithm with an UP lower bound, and establishes conditions that enable constraint learning and non-chronological backtracking in the presence of conflicts involving constraints generated by the UP lower bound. From a theorical point of view, the paper highlights the relationship between the recent UP lower bound and the well-known Maximum Independent Set (MIS) lower bound. Finally, the paper provides preliminary results that show the effectiveness of the proposed approach for representative sets of instances

Data Mining aplicado ao ITIL® para previsão do tempo de resolução de incidentes

O alinhamento entre a estratégia do negócio e a estratégia das tecnologias de informação são fatores determinantes para o sucesso de uma organização, fazendo com que exista cada vez mais uma dependência das organizações dos seus sistemas de informação (SI), como ferramenta para a implantação de novas estratégias, e como forma de garantir a continuidade das operações vitais ao negócio. Neste contexto é fácil compreender que uma organização impedida de explorar na totalidade o seu SI, devido a um incidente, é uma organização que enfrenta perdas financeiras e oportunidades de negócio, muitas vezes, irrecuperáveis. Esta situação é frequentemente agravada pela dificuldade dos profissionais de TI, na gestão das expetativas da(s) área(s) de negócio afetada(s), nomeadamente na definição de prazos de reposição de serviço, face a um incidente nos SI da organização, o que dificulta a definição de planos de contingência com vista a minimizar o impacto desse incidente. O ITIL surge como um modelo de Governo bem conhecido e muito utilizado por organizações na gestão dos seus serviços de tecnologias de informação. É hoje reconhecido como uma das abordagens mais eficazes para garantir o alinhamento com a estratégia, otimizar custos, aumentar a qualidade de serviços de TI, a satisfação dos clientes e a produtividade. Embora o ITIL preconize um processo para a gestão de Conhecimento, com o objetivo de melhorar a qualidade da tomada de decisão, a aplicabilidade deste processo e a extração efetiva de conhecimento dos dados de histórico do ciclo de vida de serviços de TI, não é um padrão e nem sempre é utilizado, pelo que existe nestes dados um manancial de conhecimento, com potencial para alavancar a eficácia dos processos de ITIL. É neste contexto, e face a esta necessidade, que o presente trabalho procurará explorar o conhecimento residente nos dados de histórico de gestão de Incidentes e com recurso a técnicas de data mining, criar um modelo que permita prever o tempo de resolução de um novo incidente. Pretende-se, deste modo, apoiar gestores e profissionais de TI, a explorarem o conhecimento residente no seu histórico de incidentes, de modo a apoiar na previsão de resolução de novos incidentes e deste modo: potenciarem a eficácia e eficiência dos serviços de TI prestados, apoiar numa melhor gestão de crise face a um incidente disruptivo, ajudar a melhor gerir as espectativas das áreas afetadas e a potenciar a ativação de planos de contingência com vista à redução de impactos. Espera-se deste modo contribuir para uma maior sinergia entre áreas de suporte e as áreas de negócio e a um aumento na satisfação pelos serviços de TI prestados. Este trabalho é um dos poucos estudos que se propõem a utilizar técnicas de data mining para estimar tempo de resolução de Incidentes, pretende-se deste modo contribuir para a disciplina de gestão de conhecimento preconizada pelo ITIL, fornecendo ferramentas e métodos que ajudem a extrair e partilhar o conhecimento, apoiando assim a qualidade na tomada de decisão e a eficácia e eficiência dos serviços de TI prestadosThe alignment between business strategy and IT strategy is a determinant factor for business success, increasing the dependency that organizations have from their Information Systems (IS), as a tool to implement new strategies and as a way to guarantee the continuity of critical business operation. In this context it is easy to understand that an organization unable to fully explore their IS, due to an incident, is an organization that faces financial loss and sometimes unrecoverable business opportunities. This circumstances are normally aggravated by the struggle IT professionals face, to manage business expectations, regarding service recovery estimations, after an incident on the organization’s IS, affecting the implementations of contingency plans, aimed to minimize the incident’s impact. The ITIL appears as a governance model well known and largely used by organizations for managing their IT services, today it is known as one of the most effectives approach to guarantee an alignment with the business strategy, to reduce costs, increase quality in IT services, customer satisfaction and productivity. Even though ITIL advocates a process for knowledge management, created to increase quality in decision making, this process effectiveness to extract knowledge from the IT live cycle data, it is not a standard and normally not used, this suggest the existence of great knowledge in this data, with potential to thrive ITIL process efficiency. This is the context and need that this study will focus, trying to extract knowledge from historical data of an incident management tool, and by using data mining technics, proposes to create a model that can predict the resolution delay for a new incident. The goal is to help managers and IT professionals, to explore the knowledge residing on their incident history so they can: increase overall performance of the IT services, to better handle crises management associated with major incident, to better manage expectations of affected business areas and to enable contingency plans and reduce impact. Hoping to contribute in a better relationship between IT and the business and to increase client satisfaction with the IT services. This study is one of the few that propose to apply data mining to forecast incidents resolution delay, the goal is to contribute to ITIL knowledge management, supplying tools and methods that help extract and share knowledge, to support in decision making and to increase IT service performance

Solving Linux Upgradeability Problems Using Boolean Optimization

Managing the software complexity of package-based systems can be regarded as one of the main challenges in software architectures. Upgrades are required on a short time basis and systems are expected to be reliable and consistent after that. For each package in the system, a set of dependencies and a set of conflicts have to be taken into account. Although this problem is computationally hard to solve, efficient tools are required. In the best scenario, the solutions provided should also be optimal in order to better fulfill users requirements and expectations. This paper describes two different tools, both based on Boolean satisfiability (SAT), for solving Linux upgradeability problems. The problem instances used in the evaluation of these tools were mainly obtained from real environments, and are subject to two different lexicographic optimization criteria. The developed tools can provide optimal solutions for many of the instances, but a few challenges remain. Moreover, it is our understanding that this problem has many similarities with other configuration problems, and therefore the same techniques can be used in other domains.Comment: In Proceedings LoCoCo 2010, arXiv:1007.083

Estimating lime requirements for tropical soils: Model comparison and development

Acid tropical soils may become more productive when treated with agricultural lime, but optimal lime rates have yet to be determined in many tropical regions. In these regions, lime rates can be estimated with lime requirement models based on widely available soil data. We reviewed seven of these models and introduced a new model (LiTAS). We evaluated the models’ ability to predict the amount of lime needed to reach a target change in soil chemical properties with data from four soil incubation studies covering 31 soil types. Two foundational models, one targeting acidity saturation and the other targeting base saturation, were more accurate than the five models that were derived from them, while the LiTAS model was the most accurate. The models were used to estimate lime requirements for 303 African soil samples. We found large differences in the estimated lime rates depending on the target soil chemical property of the model. Therefore, an important first step in formulating liming recommendations is to clearly identify the soil property of interest and the target value that needs to be reached. While the LiTAS model can be useful for strategic research, more information on acidity-related problems other than aluminum toxicity is needed to comprehensively assess the benefits of liming

Comparison of PBO solvers in a dependency solving domain

Linux package managers have to deal with dependencies and conflicts of packages required to be installed by the user. As an NP-complete problem, this is a hard task to solve. In this context, several approaches have been pursued. Apt-pbo is a package manager based on the apt project that encodes the dependency solving problem as a pseudo-Boolean optimization (PBO) problem. This paper compares different PBO solvers and their effectiveness on solving the dependency solving problem.Comment: In Proceedings LoCoCo 2010, arXiv:1007.083

Global, regional, and national burden of traumatic brain injury and spinal cord injury, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016.

Traumatic brain injury (TBI) and spinal cord injury (SCI) are increasingly recognised as global health priorities in view of the preventability of most injuries and the complex and expensive medical care they necessitate. We aimed to measure the incidence, prevalence, and years of life lived with disability (YLDs) for TBI and SCI from all causes of injury in every country, to describe how these measures have changed between 1990 and 2016, and to estimate the proportion of TBI and SCI cases caused by different types of injury. METHODS: We used results from the Global Burden of Diseases, Injuries, and Risk Factors (GBD) Study 2016 to measure the global, regional, and national burden of TBI and SCI by age and sex. We measured the incidence and prevalence of all causes of injury requiring medical care in inpatient and outpatient records, literature studies, and survey data. By use of clinical record data, we estimated the proportion of each cause of injury that required medical care that would result in TBI or SCI being considered as the nature of injury. We used literature studies to establish standardised mortality ratios and applied differential equations to convert incidence to prevalence of long-term disability. Finally, we applied GBD disability weights to calculate YLDs. We used a Bayesian meta-regression tool for epidemiological modelling, used cause-specific mortality rates for non-fatal estimation, and adjusted our results for disability experienced with comorbid conditions. We also analysed results on the basis of the Socio-demographic Index, a compound measure of income per capita, education, and fertility. FINDINGS: In 2016, there were 27·08 million (95% uncertainty interval [UI] 24·30-30·30 million) new cases of TBI and 0·93 million (0·78-1·16 million) new cases of SCI, with age-standardised incidence rates of 369 (331-412) per 100 000 population for TBI and 13 (11-16) per 100 000 for SCI. In 2016, the number of prevalent cases of TBI was 55·50 million (53·40-57·62 million) and of SCI was 27·04 million (24·98-30·15 million). From 1990 to 2016, the age-standardised prevalence of TBI increased by 8·4% (95% UI 7·7 to 9·2), whereas that of SCI did not change significantly (-0·2% [-2·1 to 2·7]). Age-standardised incidence rates increased by 3·6% (1·8 to 5·5) for TBI, but did not change significantly for SCI (-3·6% [-7·4 to 4·0]). TBI caused 8·1 million (95% UI 6·0-10·4 million) YLDs and SCI caused 9·5 million (6·7-12·4 million) YLDs in 2016, corresponding to age-standardised rates of 111 (82-141) per 100 000 for TBI and 130 (90-170) per 100 000 for SCI. Falls and road injuries were the leading causes of new cases of TBI and SCI in most regions. INTERPRETATION: TBI and SCI constitute a considerable portion of the global injury burden and are caused primarily by falls and road injuries. The increase in incidence of TBI over time might continue in view of increases in population density, population ageing, and increasing use of motor vehicles, motorcycles, and bicycles. The number of individuals living with SCI is expected to increase in view of population growth, which is concerning because of the specialised care that people with SCI can require. Our study was limited by data sparsity in some regions, and it will be important to invest greater resources in collection of data for TBI and SCI to improve the accuracy of future assessments

Acesso a Tratamento Endovascular para Acidente Vascular Cerebral Isquémico em Portugal

Introduction: Since the publication of endovascular treatment trials and European Stroke Guidelines, Portugal has re-organized stroke healthcare. The nine centers performing endovascular treatment are not equally distributed within the country, which may lead to differential access to endovascular treatment. Our main aim was to perform a descriptive analysis of the main treatment metrics regarding endovascular treatment in mainland Portugal and its administrative districts. Material and Methods: A retrospective national multicentric cohort study was conducted, including all ischemic stroke patients treated with endovascular treatment in mainland Portugal over two years (July 2015 to June 2017). All endovascular treatment centers contributed to an anonymized database. Demographic, stroke-related and procedure-related variables were collected. Crude endovascular treatment rates were calculated per 100 000 inhabitants for mainland Portugal, and each district and endovascular treatment standardized ratios (indirect age-sex standardization) were also calculated. Patient time metrics were computed as the median time between stroke onset, first-door, and puncture. Results: A total of 1625 endovascular treatment procedures were registered. The endovascular treatment rate was 8.27/100 000 inhabitants/year. We found regional heterogeneity in endovascular treatment rates (1.58 to 16.53/100 000/year), with higher rates in districts closer to endovascular treatment centers. When analyzed by district, the median time from stroke onset to puncture ranged from 212 to 432 minutes, reflecting regional heterogeneity. Conclusion: The overall national rate of EVT in the first two years after the organization of EVT-capable centers is one of the highest among European countries, however, significant regional disparities were documented. Moreover, stroke-onset-to-first-door times and in-hospital procedural times in the EVT centers were comparable to those reported in the randomized controlled trials performed in high-volume tertiary hospitals.Introdução: A aprovação do tratamento endovascular para o acidente vascular cerebral isquémico obrigou à reorganização dos cuidados de saúde em Portugal. Os nove centros que realizam tratamento endovascular não estão distribuídos equitativamente pelo território, o que poderá causar acesso diferencial a tratamento. O principal objetivo deste estudo é realizar uma análise descritiva da frequência e métricas temporais do tratamento endovascular em Portugal continental e seus distritos. Material e Métodos: Estudo de coorte nacional multicêntrico, incluindo todos os doentes com acidente vascular cerebral isquémico submetidos a tratamento endovascular em Portugal continental durante um período de dois anos (julho 2015 a junho 2017). Foram colhidos dados demográficos, relacionados com o acidente vascular cerebral e variáveis do procedimento. Taxas de tratamento endovascular brutas e ajustadas (ajuste indireto a idade e sexo) foram calculadas por 100 000 habitantes/ano para Portugal continental e cada distrito. Métricas de procedimento como tempo entre instalação, primeira porta e punção foram também analisadas. Resultados: Foram registados 1625 tratamentos endovasculares, indicando uma taxa bruta nacional de tratamento endovascular de 8,27/100 000 habitantes/ano. As taxas de tratamento endovascular entre distritos variaram entre 1,58 e 16,53/100 000/ano, com taxas mais elevadas nos distritos próximos a hospitais com tratamento endovascular. O tempo entre sintomas e punção femural entre distritos variou entre 212 e 432 minutos. Conclusão: Portugal continental apresenta uma taxa nacional de tratamento endovascular elevada, apresentando, contudo, assimetrias regionais no acesso. As métricas temporais foram comparáveis com as observadas nos ensaios clínicos piloto