Abstract: Scientific workflows are designed to solve complex scientific problems and accelerate scientific progress. Ideally, scientific workflows should improve the reproducibility of scientific applications by making it easier to share and reuse workflows between scientists. However, scientists often find it difficult to reuse others’ workflows, which is known as workflow decay. In this paper, we explore the challenges in reproducing scientific workflows, and propose a framework for facilitating the reproducibility of scientific workflows at the task level by giving scientists complete control over the execution environments of the tasks in their workflows and integrating execution environment specifications into scientific workflow systems. Our framework allows dependencies to be archived in basic units of OS image, software and data instead of gigantic all-in-one images. We implement a prototype of our framework by integrating Umbrella, an execution environment creator, into Makeflow, a scientific workflow system. To evaluate our framework, we use it to run two bioinformatics scientific workflows, BLAST and BWA. The execution environment of the tasks in each workflow is specified as an Umbrella specification file, and sent to execution nodes where Umbrella is used to create the specified environment for running the tasks. For each workflow we evaluate the size of the Umbrella specification file, the time and space overheads of creating execution environments using Umbrella, and the heterogeneity of execution nodes contributing to each workflow. The evaluation results show that our framework improves the utilization of heterogeneous computing resources, and improves the portability and reproducibility of scientific workflows.

Abstract: Integer Programming (IP) is the most successful technique for solving hard combinatorial optimization problems. Modern IP solvers are very complex programs composed of many different procedures whose execution is embedded in the generic Branch & Bound framework. The activation of these procedures as well the definition of exploration strategies for the search tree can be done by setting different parameters. Since the success of these procedures and strategies in improving the performance of IP solvers varies widely depending on the problem being solved, the usual approach for discovering a good set of parameters considering average results is not ideal. In this work we propose a comprehensive approach for the automatic tuning of Integer Programming solvers where the characteristics of instances are considered. Computational experiments in a diverse set of 308 benchmark instances using the open source COIN-OR CBC solver were performed with different parameter sets and the results were processed by data mining algorithms. The results were encouraging: when trained with a portion of the database the algorithms were able to predict better parameters for the remaining instances in 84% of the cases. The selection of a single best parameter setting would provide an improvement in only 56% of instances, showing that great improvements can be obtained with our approach.

Abstract: We present a spectrally accurate method for solving coupled singularly perturbed second order two-point boundary value problems (BVPs). The method combines analytical coordinate transformations with a standard Chebyshev spectral collocation method; it is applicable to linear and to nonlinear problems. The method performs well in resolving very thin boundary layers. Compared to other methods which had been proposed for systems of BVPs this method is competitive in terms of accuracy, allows for different perturbation parameters in each of the equations, and does not require special properties of the coefficient functions.

Abstract: An enduring topic in Information Systems academic and practitioners’ literature is how Business and Information Technology (IT) resources can be aligned in order to generate value for companies (Gerow et al. 2014). Despite a considerable body of literature, alignment is still considered an unachieved objective in corporate practice and the topic constantly ranks on top priorities of companies’ CIOs (Kappelman et al. 2013). The inability to explain the process of alignment, i.e. how alignment is implemented in organisations, is considered one of the main reasons for the high misalignment level in companies (Chan and Reich 2007b). In an attempt to radically innovate alignment studies, researchers approached Complexity Science to investigate how Information Systems evolve in organisations (Merali 2006; Merali et al. 2012; Vessey and Ward 2013; Campbell and Peppard 2007) and derived a set of principles potentially capable of improving alignment (Benbya and Mc Kelvey 2006). However, studies have mainly adopted a qualitative and descriptive approach and alignment principles have been drawn by analogy between Information Systems and other complex systems existing in nature and extensively studied rather than as the result of a theoretical explanation and modelling (Kallinikos 2005). In our study we developed a model that describes how alignment evolves in organisations. The model adopts the fraction of persons within an organisation who are unsatisfied by IT as a state variable to measure misalignment. The evolution of misalignment is linked to key parameters, such as the capacity of the IT department to understand business needs and transform them into innovation projects, the resistance to change of the personnel, the flexibility of the Information Systems, the IT investment policies of the organisation. The model is based on an extensive literature review (Chan and Reich 2007a), through which several parameters influencing alignment have been selected, and on the study of 4 cases, i.e. alignment processes implemented in manufacturing companies. Through the analysis of the model we derived principles for effectively managing alignment implementation in organisations, such as the improvement of personnel flexibility, the exploitation of feedback loops, the development of monitoring systems, and the implementation of modular, weakly-coupled IT components. Applicability of principles in corporate practice has been tested in one company undertaking a digital transformation project. The contribution to the study of alignment is twofold. The model, despite its simplicity, is capable of describing alignment dynamics, even in cases not explicable through other approaches, and contributes to the creation of a theoretical foundation for the study of alignment as a complex process. 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