Client-side resource management on the cloud: survey and future directions

Cloud computing and how to bridge the gap between various providers is getting increasing attention. In this context, efficiently scheduling tasks on heterogeneous resources is of extreme importance. The state-of-the-art for this field has been continuously growing during the last years and has reached a point in which a comprehensive overview indicating current solutions and ongoing challenges is of extreme importance for researchers. This paper aims to offer this analysis from a client-side scheduling perspective in which emphasis is not put on physical resource selection but on task to virtual machine mappings and virtual machine allocation. It provides a taxonomy for the current state-of-the-art and a unified model concerning the various metrics and goals used throughout literature. This model is designed to be sufficiently generic, extensible, and comprehensive to support most of the future work in the field. Several promising research directions and existing challenges are described

On the efficiency of several VM provisioning strategies for workflows with multi-threaded tasks on clouds

Cloud computing promises the delivery of on-demand pay-per-use access to unlimited resources. Using these resources requires more than a simple access to them as most clients have certain constraints in terms of cost and time that need to be fulfilled. Therefore certain scheduling heuristics have been devised to optimize the placement of client tasks on allocated virtual machines. The applications can be roughly divided in two categories: independent bag-of-tasks and workflows. In this paper we focus on the latter and investigate a less studied problem, i.e., the effect the virtual machine allocation policy has on the scheduling outcome. For this we look at how workflow structure, execution time, virtual machine instance type affect the efficiency of the provisioning method when cost and makespan are considered. To aid our study we devised a mathematical model for cost and makespan in case single or multiple instance types are used. While the model allows us to determine the boundaries for two of our extreme methods, the complexity of workflow applications calls for a more experimental approach to determine the general relation. For this purpose we considered synthetically generated workflows that cover a wide range of possible cases. Results have shown the need for probabilistic selection methods in case small and heterogeneous execution times are used, while for large homogeneous ones the best algorithm is clearly noticed. Several other conclusions regarding the efficiency of powerful instance types as compared to weaker ones, and of dynamic methods against static ones are also made

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Novel optimal recursive filter for state and fault estimation of linear stochastic systems with unknown disturbances

This paper studies recursive optimal filtering as well as robust fault and state estimation for linear stochastic systems with unknown disturbances. It proposes a new recursive optimal filter structure with transformation of the original system. This transformation is based on the singular value decomposition of the direct feedthrough matrix distribution of the fault which is assumed to be of arbitrary rank. The resulting filter is optimal in the sense of the unbiased minimum-variance criteria. Two numerical examples are given in order to illustrate the proposed method, in particular to solve the estimation of the simultaneous actuator and sensor fault problem and to make a comparison with the existing literature results

Exploring West African folk narrative texts using machine learning

This paper examines how machine learning (ML) and natural language processing (NLP) can be used to identify, analyze, and generate West African folk tales. Two corpora of West African and Western European folk tales are compiled and used in three experiments on cross-cultural folk tale analysis. In the text generation experiment, two types of deep learning text generators are built and trained on the West African corpus. We show that although the texts range between semantic and syntactic coherence, each of them contains West African features. The second experiment further examines the distinction between the West African and Western European folk tales by comparing the performance of an LSTM (acc. 0.74) with a BoW classifier (acc. 0.93), indicating that the two corpora can be clearly distinguished in terms of vocabulary. An interactive t-SNE visualization of a hybrid classifier (acc. 0.85) highlights the culture-specific words for both. The third experiment describes an ML analysis of narrative structures. Classifiers trained on parts of folk tales according to the three-act structure are quite capable of distinguishing these parts (acc. 0.78). Common n-grams extracted from these parts not only underline cross-cultural distinctions in narrative structures, but also show the overlap between verbal and written West African narratives

Systems Analysis of NADH Dehydrogenase Mutants Reveals Flexibility and Limits of Pseudomonas taiwanensis VLB120's Metabolism.

Obligate aerobic organisms rely on a functional electron transport chain for energy conservation and NADH oxidation. Because of this essential requirement, the genes of this pathway are likely constitutively and highly expressed to avoid a cofactor imbalance and energy shortage under fluctuating environmental conditions. We here investigated the essentiality of the three NADH dehydrogenases of the respiratory chain of the obligate aerobe Pseudomonas taiwanensis VLB120 and the impact of the knockouts of corresponding genes on its physiology and metabolism. While a mutant lacking all three NADH dehydrogenases seemed to be nonviable, the single or double knockout mutant strains displayed no, or only a weak, phenotype. Only the mutant deficient in both type 2 dehydrogenases showed a clear phenotype with biphasic growth behavior and a strongly reduced growth rate in the second phase. In-depth analyses of the metabolism of the generated mutants, including quantitative physiological experiments, transcript analysis, proteomics, and enzyme activity assays revealed distinct responses to type 2 and type 1 dehydrogenase deletions. An overall high metabolic flexibility enables P. taiwanensis to cope with the introduced genetic perturbations and maintain stable phenotypes, likely by rerouting of metabolic fluxes. This metabolic adaptability has implications for biotechnological applications. While the phenotypic robustness is favorable in large-scale applications with inhomogeneous conditions, the possible versatile redirecting of carbon fluxes upon genetic interventions can thwart metabolic engineering efforts.IMPORTANCE While Pseudomonas has the capability for high metabolic activity and the provision of reduced redox cofactors important for biocatalytic applications, exploitation of this characteristic might be hindered by high, constitutive activity of and, consequently, competition with the NADH dehydrogenases of the respiratory chain. The in-depth analysis of NADH dehydrogenase mutants of Pseudomonas taiwanensis VLB120 presented here provides insight into the phenotypic and metabolic response of this strain to these redox metabolism perturbations. This high degree of metabolic flexibility needs to be taken into account for rational engineering of this promising biotechnological workhorse toward a host with a controlled and efficient supply of redox cofactors for product synthesis

A systems analysis of NADH dehydrogenase mutants reveals flexibility and limits of Pseudomonas taiwanensis VLB120's metabolism

Obligate aerobic organisms rely on a functional electron transport chain for energy conservation and NADH oxidation. Because of this essential requirement, the genes of this pathway are likely constitutively and highly expressed to avoid a cofactor imbalance and energy shortage under fluctuating environmental conditions. We here investigated the essentiality of the three NADH dehydrogenases of the respiratory chain of the obligate aerobe VLB120 and the impact of the knockouts of corresponding genes on its physiology and metabolism. While a mutant lacking all three NADH dehydrogenases seemed to be nonviable, the generated single or double knockout strains displayed no, or only a weak, phenotype. Only the mutant deficient in both type-2 dehydrogenases showed a clear phenotype with biphasic growth behavior and a strongly reduced growth rate in the second phase. In-depth analyses of the metabolism of the generated mutants including quantitative physiological experiments, transcript analysis, proteomics, and enzyme activity assays revealed distinct responses to type-2 and type-1 dehydrogenase deletions. An overall high metabolic flexibility enables to cope with the introduced genetic perturbations and maintain stable phenotypes, likely by re-routing of metabolic fluxes. This metabolic adaptability has implications for biotechnological applications. While the phenotypic robustness is favorable in large-scale applications with inhomogeneous conditions, the possible versatile redirecting of carbon fluxes upon genetic interventions can thwart metabolic engineering efforts. While has the capability for high metabolic activity and the provision of reduced redox cofactors important for biocatalytic applications, exploitation of this characteristic might be hindered by high, constitutive activity of and, consequently, competition with the NADH dehydrogenases of the respiratory chain. The in-depth analysis of NADH dehydrogenase mutants of VLB120 presented here, provides insight into the phenotypic and metabolic response of this strain to these redox metabolism perturbations. The observed great metabolic flexibility needs to be taken into account for rational engineering of this promising biotechnological workhorse towards a host with controlled and efficient supply of redox cofactors for product synthesis