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Mobile Information Management 2004

作者： Grünbauer, Johannes Klein, Michael Institut für Informatik Technische Universität München Garching85748 Germany Institute for Program Structures and Data Organization Universität Karlsruhe Karlsruhe76128 Germany

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Reducing search space of auto-tuners using parallel patterns

Reducing search space of auto-tuners using parallel patterns

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ICSE Workshop on Multicore Software Engineering, IWMSE

作者： Christoph A. Schaefer Institute of Program Structures and Data Organization University of Karlsruhe Karlsruhe Germany

ISBN: (纸本)9781424437184

Auto-tuning is indispensable to achieve best performance of parallel applications, as manual tuning is extremely labor intensive and error-prone. Search-based auto-tuners offer a systematic way to find performance optimums, and existing approaches provide promising results. However, they suffer from large search spaces. In this paper we propose the idea to reduce the search space using parameterized parallel patterns. We introduce an approach to exploit context information from Master/Worker and Pipeline patterns before applying common search algorithms. The approach enables a more efficient search and is suitable for parallel applications in general. In addition, we present an implementation concept and a corresponding prototype for pattern-based tuning. The approach and the prototype have been successfully evaluated in two large case studies. Due to the significantly reduced search space a common hill climbing algorithm and a random sampling strategy require on average 54% less tuning iterations, while even achieving a better accuracy in most cases.

关键词： Pipelines Prototypes Sampling methods Testing Yarn Tuners Libraries Performance gain Performance evaluation Predictive models

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Roger that! Learning How Laypersons Teach New Functions to Intelligent Systems

Roger that! Learning How Laypersons Teach New Functions to I...

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International Conference on Semantic Computing

作者： Sebastian Weigelt Vanessa Steurer Tobias Hey Walter F. Tichy Karlsruhe Institute of Technology Institute for Program Structures and Data Organization Karlsruhe Germany

ISBN: (数字)9781728163321

ISBN: (纸本)9781728163338

Intelligent systems are rather smart today but still limited to built-in functionality. To break through this barrier, future systems must allow users to easily adapt the system by themselves. For humans the most natural way to communicate is talking. But what if users want to extend the systems' functionality with nothing but natural language? Then intelligent systems must understand how laypersons teach new skills. To grasp the semantics of such teaching sequences, we have defined a hierarchical classification task. On the first level, we consider the existence of a teaching intent in an utterance; on the second, we classify the distinct semantic parts of teaching sequences: declaration of a new function, specification of intermediate steps, and superfluous information. We evaluate twelve machine learning techniques with multiple configurations tailored to this task ranging from classical approaches such as naïve-bayes to modern techniques such as bidirectional LSTMs and task-oriented adaptations. On the first level convolutional neural networks achieve the best accuracy (96.6%). For the second task, bidirectional LSTMs are the most accurate (98.8%). With the additional adaptations we are able to improve both classifications distinctly (up to 1.8%).

关键词： Task analysis Semantics Neural networks Machine learning Intelligent systems Training

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Verification of data-Value-Aware Processes and a Case Study on Spectrum Auctions

Verification of Data-Value-Aware Processes and a Case Study ...

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IEEE Conference on Commerce and Enterprise Computing, CEC

作者： Elaheh Ordoni Jutta Mülle Klemens Böhm Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Karlsruhe Germany

ISBN: (数字)9781728199269

ISBN: (纸本)9781728199276

Verification techniques are fundamental to improve the reliability of process designs in practice. In application domains like auctions, the issue is extremely valuable; the goal of auction designers is to prevent undesirable executions and maximize certain outcome measures. Current verification approaches tend to be confined to control flows, even though data values play a significant role. We address this issue by proposing a new data-value-aware verification approach: We enhance process models with information on data values. Then we transform the data-value-aware process models to Petri Nets, respecting the semantics of data value usages. By employing an off-the-shelf model checker and specifying data-value centered properties, one can now verify data-value-aware process models. A distinctive feature of our approach is the specification of data values and of their modifications during the process. This enables the verification of interesting properties in many domains. We evaluate our approach against the use case of Simultaneous Multi-Round (SMR) spectrum auctions. We verify SMR auction models and compute extreme values of common auction measures such as revenue.

关键词： Petri nets data models Licenses Computational modeling Reliability engineering Space exploration

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The Architecture of a Secure Business-Process-Management System in Service-Oriented Environments

The Architecture of a Secure Business-Process-Management Sys...

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European Conference on Web Services (ECOWS)

作者： Jens Muller Klemens Bohm Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Karlsruhe Germany

Business-process-management (BPM) systems are increasingly used in service-oriented architectures (SOA), coordinating activities of web services and of human actors. The openness and flexibility of SOA causes new challenges regarding security of business processes. This is because they have to deal with unexpected situations at run time. Respective solutions must be inherent to a BPM system (BPMS). Process implementers must explicitly model different security aspects of business processes, and the BPMS must combine them with run-time context to enforce security. However, existing BPMS do not address security issues in a way that is sufficiently broad. Thus, extensions are necessary, and they should integrate existing technology. The core contribution of this paper is to propose how to extend the WfMC reference architecture for BPMS to accomplish this, having identified different design alternatives. The resulting architecture is generic and integrates with existing SOA technologies like federated identity management. It is modular, making adaptations relatively easy. This has been hard to achieve because security aspects concern the entire system. Finally, our architecture can be used to implement the various business process security modelling approaches that have been presented in the literature.

关键词： Context Service oriented architecture Humans Business Authorization

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Secure Business Processes in Service-Oriented Architectures -- A Requirements Analysis

Secure Business Processes in Service-Oriented Architectures ...

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European Conference on Web Services (ECOWS)

作者： Jens Muller Jutta Mulle Silvia von Stackelberg Klemens Bohm Institute of Program Structures and Data Organization Karlsruhe Institute of Technology Karlsruhe Germany

Business-process-management systems are increasingly used in service-oriented architectures (SOA), coordinating activities of loosely coupled information systems, of web services, and of human actors. This often requires exchanging and processing sensitive, personally-identifiable information, e.g., in e-employability and e-health applications. Supporting security in such a service-oriented environment is challenging. Existing approaches focus on security in service-oriented architectures but neglect business-process specific characteristics. Motivated by a real-world business process from the e-employability domain, in this paper we collect security requirements, exploiting the specific properties and semantics of business processes. We evaluate the requirements with respect to the state of the art of suitable security mechanisms and identify possible solutions as well as remaining gaps. We see this article as an important prerequisite for the design and implementation of advanced security mechanisms for business processes.

关键词： Business Access control Service oriented architecture Authentication Humans

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Locating Parallelization Potential in Object-Oriented data structures

Locating Parallelization Potential in Object-Oriented Data S...

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IEEE International Parallel and Distributed Processing Symposium

作者： Korbinian Molitorisz Thomas Karcher Alexander Bieles Walter F. Tichy Institute for Program Structures and Data Organization (IPD) Karlsruhe Institute of Technology (KIT)

ISBN: (纸本)9781479938018

The free lunch of ever increasing single-processor performance is over. Software engineers have to parallelize software to gain performance improvements. But not every software engineer is a parallel expert and with millions of lines of code that have not been developed with multicore in mind, we have to find ways to assist in identifying parallelization potential. This paper makes three contributions: 1) An empirical study of more than 900,000 lines of code reveals five use cases in the runtime profile of object-oriented data structures that carry parallelization potential. 2) The study also points out frequently used data structures in realistic software in which these use cases can be found. 3) We developed DSspy, an automatic dynamic profiler that locates these use cases and makes recommendations on how to parallelize them. Our evaluation shows that DSspy reduces the search space for parallelization by up to 77% and engineers only need to consider 23% of all data structure instances for parallelization.

关键词： Parallelization Detection Dynamic Analysis Tool

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A study of the impact of structure on cooperation in networks

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Web Intelligence and Agent Systems 2011年第3期9卷 269-288页

作者： Schosser, Stephan Böhm, Klemens Vogt, Bodo Institute of Economic Theory and Statistics Karlsruhe Institute of Technology Zirkel 2 76128 Karlsruhe Germany Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Am Fasanengarten 5 76131 Karlsruhe Germany Faculty of Economics Empirical Economics Otto-von-Guericke Universität Magdeburg Universitätsplatz 2 39106 Magdeburg Germany

The concern of this paper is that nodes in a distributed system cooperate. We demonstrate that adding structure to such systems can help to induce cooperation. 'Adding structure' means bounding the number of nodes a node can directly interact with - if two unconnected nodes wish to interact, they have to do so via a chain of intermediaries which are connected. To validate our claim, we analyze one specific system where structure has been added. Different methods exist for such analyses: Economists use behavioral experiments to study human behavior. Computer scientists rely on simulations, to obtain results that are robust and scalable. Both use game theory to arrive at formal results. Each approach in isolation has its disadvantages: Behavioral experiments do not allow analyzing many different combinations of parameter values and do not scale well. Game theory supports analyzing system equilibria, but may result in complex or even unsolvable models, in particular when considering system dynamics. Simulations rely on the intuition of the system designer - this is hazardous in strategic settings. We pursue a combination of these approaches and show that the degree of cooperation in our setting is high. More specifically, after having shown with behavioral experiments that humans tend to use cut-off strategies, we translate the strategies used into a game theoretic model and show that they yield an efficient equilibrium. Simulations show that the system reaches this equilibrium given random start populations if the rate of free riders is low. We conclude by saying how our work affects the design of distributed systems from a computer science perspective. © 2011 - IOS Press and the authors. All rights reserved.

关键词： Game theory

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Online-Autotuning in the Presence of Algorithmic Choice

Online-Autotuning in the Presence of Algorithmic Choice

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IEEE International Symposium on Parallel and Distributed Processing Workshops and Phd Forum (IPDPSW)

作者： Philip Pfaffe Martin Tillmann Sigmar Walter Walter F. Tichy Karlsruhe Institute of Technology (KIT) Institute for Program Structures and Data Organization Karlsruhe Germany

In this paper we explore the problem of autotuning the choice of algorithm. For a given task, there may be multiple algorithms available, each of which may contain its own set of tunable parameters and may provide optimal performance under different sets of inputs. Algorithmic choice is a type of tuning parameter which has not been well studied in the history of autotuning. To close this gap, we examine established autotuning techniques with regard to their ability of handling these parameters. We discuss the inadequacy of the state-of-the-art autotuning toolbox in manipulating algorithmic choice parameters and introduce four strategies to tackle this task. We evaluate our strategies in two case studies of online-autotuning scenarios, both with and without additional, numeric tuning parameters. The strategies are able to determine the optimal algorithm, and can even interoperate with the autotuning of the additional parameters.

关键词： Tuning Algorithm design and analysis Runtime Optimization Genetic algorithms Approximation algorithms Classification algorithms

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Improving Traceability Link Recovery Using Fine-grained Requirements-to-Code Relations

Improving Traceability Link Recovery Using Fine-grained Requ...

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International Conference on Software Maintenance (ICSM)

作者： Tobias Hey Fei Chen Sebastian Weigelt Walter F. Tichy Karlsruhe Institute of Technology (KIT) Institute for Program Structures and Data Organization Karlsruhe Germany

Traceability information is a fundamental prerequisite for many essential software maintenance and evolution tasks, such as change impact and software reusability analyses. However, manually generating traceability information is costly and error-prone. Therefore, researchers have developed automated approaches that utilize textual similarities between artifacts to establish trace links. These approaches tend to achieve low precision at reasonable recall levels, as they are not able to bridge the semantic gap between high-level natural language requirements and code. We propose to overcome this limitation by leveraging fine-grained, method and sentence level, similarities between the artifacts for traceability link recovery. Our approach uses word embeddings and a Word Mover's Distance-based similarity to bridge the semantic gap. The fine-grained similarities are aggregated according to the artifacts structure and participate in a majority vote to retrieve coarse-grained, requirement-to-class, trace links. In a comprehensive empirical evaluation, we show that our approach is able to outperform state-of-the-art unsupervised traceability link recovery approaches. Additionally, we illustrate the benefits of fine-grained structural analyses to word embedding-based trace link generation.

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