Infrastructure for Performance Monitoring and Analysis of Systems and Applications

The growth of High Performance Computer (HPC) systems increases the complexity with respect to understanding resource utilization, system management, and performance issues. HPC performance monitoring tools need to collect information at both the application and system levels to yield a complete performance picture. Existing approaches limit the abilities of the users to do meaningful analysis on actionable timescale. Efficient infrastructures are required to support largescale systems performance data analysis for both run-time troubleshooting and post-run processing modes. In this dissertation, we present methods to fill these gaps in the infrastructure for HPC performance monitoring and analysis. First, we enhance the architecture of a monitoring system to integrate streaming analysis capabilities at arbitrary locations within its data collection, transport, and aggregation facilities. Next, we present an approach to streaming collection of application performance data. We integrate these methods with a monitoring system used on large-scale computational platforms. Finally, we present a new approach for constructing durable transactional linked data structures that takes advantage of byte-addressable non-volatile memory technologies. Transactional data structures are building blocks of in-memory databases that are used by HPC monitoring systems to store and retrieve data efficiently. We evaluate the presented approaches on a series of case studies. The experiment results demonstrate the impact of our tools, while keeping the overhead in an acceptable margin

Quantum Chemical Studies on Bonding and Reactivity at Hybrid Organic-Inorganic Interfaces

In this cumulative dissertation organic-inorganic hybrid interfaces with relevance for nanoelectronic applications are investigated with theoretical methods. An emphasis is put on the elucidation of interface reaction mechanisms and the employment of bonding analysis to better inform synthetic design choices. Furthermore, electronic structure related properties are calculated in order to explain experimental observations. The dissertation is organized in two parts. In the first part, the covalent attachment of organic layers on the (001) facet of the inorganic semiconductor silicon is studied. The second part is concerned with the creation of interface models for organic semiconductors on Ag(111). In the past it was shown that cyclooctyne is a particularly suitable platform molecule for the purpose of creating a contact layer with Si(001) due to its highly selective adsoption. Building on this prior work, the focus of this dissertation is hence the growth of a second layer on the contact layer. For this purpose, promising reactions schemes with “click”-characteristics (fast, excellent yield, solvent tolerant) are studied. These are the azide-alkyne cycloaddition (AAC), the enolether-tetrazine inverse electron demand Diels-Alder reaction (IEDDA) as well as the nucleophilic substitutions of an acid chloride mediated esterification (ACE) and the sulfonylfluoride exchange (SuFEx). The second main topic of this dissertation is the chemical interplay of the Ag(111) surface with nature inspired organic semiconductors based on pyrrole units. In comparison to silicon, the coinage metal surface has a comparatively low reactivity. This property is crucial for keeping the π-systems of the organic semiconductors intact after interface formation. Still, various bonding patterns can emerge at the interface. Besides van der Waals interactions, an exchange of electron density between the surface and the organic π-system is observed. The strength of this interaction is determined primarily by the frontier orbitals of the molecule. In summary, the collected work of this dissertation shows that quantum chemical methods are a valuable tool for better understanding the chemistry and electronic structure of hybrid interfaces. Insights gained from theory not only explain experimental observations but can also be used to guide synthetic efforts even though, different terminologies and concepts exist for metal and semiconductor surfaces. Furthermore, the studies presented here highlight that various types of interfaces can be described efficiently within an ab inito framework