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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Compiler Transformations For Improving The Performance Of Software Transactional Memory

Mannarswamy, Sandya S 11 1900 (has links) (PDF)
Expressing synchronization using traditional lock based primitives has been found to be both error-prone and restrictive. Hence there has been considerable research work to develop scalable and programmer-friendly alternatives to lock-based synchronization. Atomic sections have been proposed as a programming idiom for expressing synchronization at a higher-level of abstraction than locks. One way of supporting atomic sections in software is to rely on an underlying Software Transactional Memory (STM) implementation. While STM offers the promise of being a programming paradigm which is less error-prone and more programmer friendly compared to traditional lock-based synchronization, it also needs to be competitive in performance in order for it to be adopted in mainstream software. Unfortunately STMs do not meet the performance goals and are known to incur excessive performance overheads. Prior work by other researchers and our performance analysis of STM applications show that conflicts and the resulting aborts are a major performance bottleneck for STM applications. Second we find that, supporting fine-grained optimistic concurrency can have significant impact on the cache behavior of applications running on STM and hence can adversely affect STM performance. Our systematic quantitative analysis of the cache behavior of STM applications as well as prior work on qualitative analysis of STM overheads show that cache overheads constitute a major performance bottleneck for STM applications. Hence in this thesis, we focus on addressing these two major STM performance bottlenecks. Current STM implementations are typically application unaware in that they do not analyze the application and use that knowledge to improve the application performance on STM. Closer integration of transactions with the programming languages opens up the possibility of using the compiler to analyze STM applications and using that knowledge to perform application code transformations to improve the application performance on STM automatically and in a manner transparent to the programmer. This motivated us to address the two major STM performance bottlenecks namely poor cache performance and performance penalty due to aborts, by compiler transformations. In order to pinpoint the cache bottlenecks of STM, we perform a detailed experimental evaluation of the cache behavior of STM applications and quantify the impact of the different STM factors on the cache misses experienced by the applications. We propose a set of compiler transformations targeted to address the cache performance bottlenecks identified by our analysis. Next we turn our attention to compiler analysis and transformations targeted at reducing the performance overheads due to transactional aborts, effectively utilizing the compiler’s knowledge of the data access patterns of the application. Since not all applications are designed with optimistic concurrency in mind, real world applications typically contain certain atomic sections which are not amenable to STM’s optimistic concurrency control and hence suffer from excessive transactional abort overheads. We propose two compiler techniques for handling such atomic sections. Another major cause of transactional conflicts leading to unnecessary aborts is the uniform granularity access tracking scheme employed by STM implementations. Using a single uniform access tracking granularity leads to poor lock assignment by STM. We propose techniques which use compiler’s knowledge of an application to improve the application unaware lock assignment made by the STM. Last as transactional abort overheads impact STM performance adversely, we propose a compiler-based approach to reduce the transactional abort overheads by reconciling certain kinds of transactions instead of aborting them and then performing a complete re-execution. We show that our combined set of compiler transformations are effective in improving the performance of a set of STAMP benchmarks by reducing the execution time by 7.48% to 54.82%, aborts by 8.98% to 56.61% and the average D-cache miss latency by up to 33.51%.
82

Can Leaders Influence a Learning Organization? An Exploratory Study of the Relationship Between Leadership, Organizational Learning Capability and the Mediating Role of Trust

Grover, Ira Ann January 2012 (has links)
The purpose of this research is to study how organizations maintain their competitive advantage in today’s turbulent and highly competitive business environment, by striving to become a learning organization. The impact of factors such as leadership (both transformational and transactional leadership) and trust on an organization’s learning capability is empirically examined. This research adds to the existing body of literature in two ways. First, it argues that a transactional leadership style can influence learning, despite research spanning the last decade that has focused on transformational leadership theory as the dominant model of effective leadership. Therefore, the importance of both leadership styles, each having valuable differential effects is emphasized in this study. Second, the previously untested role of trust as mediating the relationship between leadership and organizational learning capability is examined. It is argued that without supervisor trust, the opportunities for a learning organization to reach its full potential and to subsequently develop learning capabilities is reduced. Findings from this study support the influence of both leadership styles on learning. Trust in one’s supervisor was also found to fully mediate the relationship between leadership and learning.
83

Teorie firmy - založení a existence firmy / Theory of the firm - establishing and company existence

Říha, Jakub January 2012 (has links)
The main topic of this thesis is the theory of the firm, why are companies set up and how the company is perceived by those who founded it, therefore entrepreneurs. The main question is, if the theory that builds a theory based on the company's transaction cost savings, corresponds to reality, what are the real reasons for entrepreneurs starting a business and what options future entrepreneurs have. The first part focuses on the analysis of economic theory, which deals with the company, and the ideas of economists whose work has been fundamental for the development of theory of the firm. Among the pioneers we include R.H.Coase and his disciples, such as OE Williamson, O. Hart and others. The result of the work of these authors is the theory of transaction cost savings as the main reasons for the establishment of firms, along with the other supporting reasons. Next follows an extensive legal analysis of the most important forms of business entities, especially the conditions for their establishment. This section is important for understanding the differences between legal and economic conception of the company. The most important forms of business in terms of this thesis are self-employed and limited liability company, for which there is devoted the largest part. Rozhodni si, kterou vetu chces. Another section contains an analysis of transaction costs that arise in the company. We identify the principal moments when transaction costs are incurred and what variables affect them. Since these costs are highly subjective in nature, it is described here as an example of how the situation may appear in various corporate structures. The last part of this thesis is the survey, which identifies the main reasons for the establishment of the company and how it is perceived by entrepreneurs and non-entrepreneurs. The result is supported by the conclusions of the previous chapters defining the reason for the establishment of a company outside the theory of transaction costs, which are particularly important for the further development of the company and not for the establishment itself.
84

Real-Time Software Transactional Memory: Contention Managers, Time Bounds, and Implementations

El-Shambakey, Mohammed Talat 02 October 2013 (has links)
Lock-based concurrency control suffers from programmability, scalability, and composability challenges. These challenges are exacerbated in emerging multicore architectures, on which improved software performance must be achieved by exposing greater concurrency. Transactional memory (TM) is an emerging alternative synchronization model for shared memory objects that promises to alleviate these difficulties. In this dissertation, we consider software transactional memory (STM) for concurrency control in multicore real-time software, and present a suite of real-time STM contention managers for resolving transactional conflicts. The contention managers are called ECM, RCM, LCM, PNF, and FBLT. RCM and ECM resolve conflicts using fixed and dynamic priorities of real-time tasks, respectively, and are naturally intended to be used with the fixed priority (e.g., G-RMA) and dynamic priority (e.g., G-EDF) multicore real-time schedulers, respectively. LCM resolves conflicts based on task priorities as well as atomic section lengths, and can be used with G-EDF or G-RMA schedulers. Transactions under ECM, RCM, and LCM may retry due to conflicts with higher priority tasks even when there are no shared objects, i.e., transitive retry. PNF avoids transitive retry and optimizes processor usage by lowering the priority of retrying transactions, thereby enabling other non-conflicting transactions to proceed. PNF, however, requires a priori knowledge of all requested objects for each atomic section, which is inconsistent with the semantics of dynamic STM. Moreover, its centralized design increases overhead. FBLT avoids transitive retry, do not require a priori knowledge of requested objects, and has a decentralized design. We establish upper bounds on transactional retry costs and task response times under the contention managers through schedulability analysis. Since ECM and RCM preserve the semantics of the underlying real-time scheduler, their maximum transactional retry cost is double the maximum atomic section length. This is improved in the design of LCM, which achieves shorter retry costs and tighter upper bounds. As PNF avoids transitive retry and improves processor usage, it yields shorter retry costs and tighter upper bounds than ECM, RCM, and LCM. FBLT\'s upper bounds are similarly tight because it combines the advantages of PNF and LCM. We formally compare the proposed contention managers with each other, with lock-free synchronization, and with multiprocessor real-time locking protocols. Our analysis reveals that, for most cases, ECM, RCM, and LCM achieve higher schedulability than lock-free synchronization only when the atomic section length does not exceed half of lock-free synchronization\'s retry loop length. With equal periods and greater access times for shared objects, atomic section length under ECM, RCM, and LCM can be much larger than the retry loop length while still achieving better schedulability. With proper values for LCM\'s design parameters, atomic section length can be larger than the retry loop length for better schedulability. Under PNF, atomic section length can exceed lock-free\'s retry loop length and still achieve better schedulability in certain cases. FBLT achieves equal or better schedulability than lock-free with appropriate values for design parameters. The schedulability advantage of the contention managers over multiprocessor real-time locking protocols such as Global OMLP and RNLP depends upon the value of $s_{max}/L_{max}$, the ratio of the maximum transaction length to the maximum critical section length. FBLT\'s schedulability is equal or better than Global OMLP and RNLP if $s_/L_ le 2$. Checkpointing enables partial roll-back of transactions by recording transaction execution states (i.e., checkpoints) during execution, allowing roll-back to a previous checkpoint instead of transaction start, improving task response time. We extend FBLT with checkpointing and develop CP-FBLT, and identify the conditions under which CP-FBLT achieves equal or better schedulability than FBLT. We implement the contention managers in the Rochester STM framework and conduct experimental studies using a multicore real-time Linux kernel. Our studies reveal that among the contention managers, CP-FBLT has the best average-case performance. CP-FBLT\'s higher performance is due to the fact that PNF\'s and LCM\'s advantages are combined into the design of FBLT, which is the base of CP-FBLT. Moreover, checkpointing improves task response time. The contention managers were also found to have equal or better average-case performance than lock-free synchronization: more jobs meet their deadlines using CP-FBLT, FBLT, and PNF than lock-free synchronization by 34.6%, 28.5%, and 32.4% (on average), respectively. The superiority of the contention managers is directly due to their better conflict resolution policies. Locking protocols such as OMLP and RNLP were found to perform better: more jobs meet their deadlines under OMLP and RNLP than any contention manager by 12.4% and 13.7% (on average), respectively. However, the proposed contention managers have numerous qualitative advantages over locking protocols. Locks do not compose, whereas STM transactions do. To allow multiple objects to be accessed in a critical section, OMLP assigns objects to non-conflicting groups, where each group is protected by a distinct lock. RNLP assumes that objects are accessed in a specific order to prevent deadlocks. In contrast, STM allows multiple objects to be accessed in a transaction in any order, while guaranteeing deadlock-freedom, which significantly increases programmability. Moreover, STM offers platform independence: the proposed contention managers can be entirely implemented in the user-space as a library. In contrast, real-time locking protocols such as OMLP and RNLP must be supported by the underlying platform (i.e., operating system or virtual machine). / Ph. D.
85

Exploring Short Text Clustering for Transactional Data

Annerwall, Staffan January 2021 (has links)
The digital revolution has led to an increase in digitization of transactional information. Due to the large amount of data, the transactions must be categorized such that an overview of spending can be obtained. To aid the process of manually classifying transactions, we consider a process of clustering short text transactional data as a pre-processing step. If clusters have high homogeneity, then entire clusters, and hence multiple transactions, can be classified at once. We explore two short text clustering methods, and evaluate them on real-world data in terms of execution time and clustering performance determined by domain experts. In the evaluations results, the clusterings exhibit poor intra-cluster similarity (i.e. homogeneity), and are deemed unusable. One of the algorithms is extremely slow, but this is likely due to insufficient memory capacity of the evaluation environment. We conclude that the chosen methods are unsuitable for our purposes and discuss the properties that other clustering techniques should have in order to be suitable. We also discuss non-clustering approaches that may be suitable.
86

The blesser-blessee relationship : a pastoral challenge

Frieslaar, Brent V. January 2019 (has links)
For many young women, life can be an overwhelming, stressful and challenging experience. The increase in the cost of living and high costs of education places a huge financial burden on the parents of these young women especially those who are financially insecure and who have unfortunately not been awarded bursaries or student loans. Many have to find means of income in order to fund their studies and/or eke out a living. Older men who are wealthy have been found to take advantage of these realities and they seek out young women who are struggling financially and “bless” them by providing for their financial needs. Some older men even go beyond these offerings and lavish the young women with other luxury items. Young women see these men as caring and loving and also as a practical escape from financial burdens they face. The older men, called “blessers’”, seek return on their blessings and this is often in the form of sexual favours. The young women are expected to satisfy the sexual desires of their blessers, often at great personal cost and endless sacrifices. This exposes young women to sexual exploitation and abuse. This research seeks to gain a better understanding of the phenomenon and why women engage in these relationships and why some remain in these relationships. It also seeks to create awareness of the dangers of these relationships within the context of the church and to empower young women with a healthy sense of selfworth and value in order to make safer and informed life decisions and to pastorally care for those who have experienced trauma. As a result of the understanding gained through narrative approach, the researcher seeks to begin the process of developing a pastoral care and healing methodology/intervention method. / Dissertation (MTh)--University of Pretoria, 2019. / Practical Theology / MTh / Unrestricted
87

Perceptions of Leadership: Impact of Leadership Style and Gender on Employee Motivation

Walker, Kristin Marquette 01 January 2015 (has links)
Researchers suggest that individuals in Corporate America have stereotypes about the ways in which men and women lead. They also have found that a leader's style and gender can impact employees' job satisfaction, performance, and engagement. However, researchers have provided little empirical evidence about the specific relationship of leadership style and gender on employee motivation. The purpose of this quantitative study was to examine the effects of leadership style, as measured by the Multifactor Leadership Questionnaire (MLQ), and a leader's gender on employee motivation, as measured by the Work Preference Inventory (WPI). Because it was assumed that small organizations would elicit higher participation, individuals employed at organizations with fewer than 100 employees were surveyed. After being asked about the gender and specific characteristics of their leaders, participants were asked about their level of motivation via the WPI. A 2x3 ANOVA was performed to determine the main effects of a leader's gender and leadership style on level of employee motivation. Findings revealed that although gender and leadership style do not significantly impact motivation, laissez-faire leadership style is more likely to positively influence motivation when compared to transformational or transactional leadership style. Though statistically insignificant, these findings contribute to the understanding of the relationship of gender, leadership, and employee motivation, an ongoing topic of concern. Social implications of this study include dispelling some of the gender stereotypes distributed by Corporate America. Essentially, effective leadership is not about which gender leads best, but more about deploying leadership skills that will contribute to employee success.
88

Transactional distance in a synchronous web-extended classroom learning environment

Rabinovich, Tamara January 2009 (has links)
Thesis (Ed.D.)--Boston University / This study aimed at refining one of the most influential and well-known theories of distance education - the theory of transactional distance (TD). TD theory was developed by Michael G. Moore based on correspondence forms of distance education. The study researched a distance learning environment that had not been investigated in relation to TD - synchronous Web-extended classrooms. In this unique format, live on- campus classes are delivered simultaneously to both in-class students on campus and remote students on the Web who attend synchronously via virtual classroom Web collaboration software. The research involved N=235 students enrolled in 14 graduate business courses. ANOVA tests, correlation and regression analyses were deployed on the 46-item "Scale of TD for synchronous Web-extended learning environments" questionnaire. The study compared perceived TD for three attendance groups: always in-class, always online, and mixed. It found no difference in TD among them. The learning environment enabled by using Saba-Centra Web collaboration software combined with other technologies provided a comparable learning experience for all three learner groups. The findings confirmed that four dimensions of dialogue, student-student, student-instructor, student-content, and student-interface interactions are significant in students' perceived TD and their engagement with learning. Moreover, their significance levels varied for different attendance groups. This research confirms the need to refine TD theory to view dialogue as a multidimensional construct. Furthermore, student-instructor and student-student interactions were significant factors that affected TD in all three learner groups. This study analyzed student satisfaction. The study not only found no difference in satisfaction by attendance type, but also it found that TD is strongly related to student satisfaction: the lower the TD, the more satisfied the students are with the learning environment, including interactions with the instructor, fellow students, course content, and the interface. For all attendance groups, interaction with other students was the common factor that affected satisfaction. The study demonstrated that the level of TD also affects students' perceived learning: the lower the TD, the higher the students' perceived learning. Thus, the study suggests that instructors plan activities that include interpersonal interactions between themselves and students, and also among students in all attendance groups.
89

Att tillverka delar till någon annans tillverkning. : Ett arbete om Alienation / To manufacture parts for someone else's manufacturing : A work on alienation

Ohlson, Anders, Paulsson, Elin January 2023 (has links)
The purpose of this study is to examine how the company work to prevent alienationamong the employees. One very important part of this is how the leadership works in theexamined company and we have studied the leadership as a tool to prevent alienation.When we went through previous research on the subject, we found that the companypractice transformative leadership and we included that theory to our work. Furthermore,we investigate to what extent the various leaders practice transformative leadership howthis is connected to alienation. Finally, whether the company's high-performance teamscan be seen as successful and whether the success is linked to transformative leadership.The empirical data was collected by interviewing twelve people in the company, sevenmanagers and five co-workers. The analysis was made in two steps. First we examinedhow the company’s leadership model work and if it’s connected to the high-performanceteams. (Forslund, 2022). Second, how this effects the alienation at the company. Theresult was that transformative leadership indeed is included in the company’s leadershipmodel. Furthermore, we could conclude that the leaders in the company did practisetransformative leadership, even though the level varied a little between the individualleaders. The transformative leadership is effective in preventing alienation and weconclude that it is the most important tool in the process of preventing that. Finally, wesee that the company’s model, and practise of leadership is successful.
90

A sensemaking perspective on the psycological contract formations during organisational socialisation.

Magang, Veronica G. January 2009 (has links)
The main aim of this thesis is to investigate the processes of the psychological contract during organisational socialisation. Research on psychological contract tends to focus more on the content and breach of the contract. Very little is known about the formative stages of the contract. Very little attention has also been given to investigating the psychological contract together with organisational socialisation. Linking the two research areas would further our understanding of both the dynamic nature of the psychological contract. This is achieved by investigating the temporal changes of the psychological contract of new employees, pre-entry up to six months post entry into employment. The research also investigates the psychological contract from the employer`s perspective. It utilises Weick`s (1995) sensemaking properties as a methodological framework to better understand these processes. Consistent with the research aim and objectives and social constructionism, a qualitative methodology was adopted. The research used in-depth semi structured interviews to collect data supplemented with sitting in during recruitment interviews in one of the organisations, and data were analysed using template analysis. Periodic interviews were carried out every four to six months post entry. The research consists of two organisations, where each provided two groups for analysis. The findings show that after entry into the organisation, the psychological contract changes in a variety of ways influenced by socialisation into the organisation. A model based on the findings is presented and discussed in the discussion chapter. The research also makes a contribution (methodology) by adopting the sensemaking framework.

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