An Efficient Data Structure for Dynamic Two-Dimensional Reconfiguration

In the presence of dynamic insertions and deletions into a partially reconfigurable FPGA, fragmentation is unavoidable. This poses the challenge of developing efficient approaches to dynamic defragmentation and reallocation. One key aspect is to develop efficient algorithms and data structures that exploit the two-dimensional geometry of a chip, instead of just one. We propose a new method for this task, based on the fractal structure of a quadtree, which allows dynamic segmentation of the chip area, along with dynamically adjusting the necessary communication infrastructure. We describe a number of algorithmic aspects, and present different solutions. We also provide a number of basic simulations that indicate that the theoretical worst-case bound may be pessimistic.Comment: 11 pages, 12 figures; full version of extended abstract that appeared in ARCS 201

On Lazy Bin Covering and Packing problems

AbstractIn this paper, we study two interesting variants of the classical bin packing problem, called Lazy Bin Covering (LBC) and Cardinality Constrained Maximum Resource Bin Packing (CCMRBP) problems. For the offline LBC problem, we first prove the approximation ratio of the First-Fit-Decreasing and First-Fit-Increasing algorithms, then present an APTAS. For the online LBC problem, we give a competitive analysis for the algorithms of Next-Fit, Worst-Fit, First-Fit, and a modified HARMONICM algorithm. The CCMRBP problem is a generalization of the Maximum Resource Bin Packing (MRBP) problem Boyar et al. (2006) [1]. For this problem, we prove that its offline version is no harder to approximate than the offline MRBP problem

TOWARDS THE RATIONAL DESIGN OF ORGANIC SEMICONDUCTORS THROUGH COMPUTATIONAL APPROACHES

Though organic semiconductors have illustrated potential as industry-relevant materials for electronics applications, there are few guidelines that can take one from molecular design to functional materials. This limitation is, in part, due to incomplete understanding as to how the atomic-scale construction of the π-conjugated molecules that comprise the organic semiconductors determines the nature and strength of both the noncovalent intramolecular interactions that govern molecular conformation and noncovalent intermolecular interactions that regulate the energetic preference for solid-state packing. Hence, there remain several fundamental questions that need to be resolved in order to design organic semiconductors from a priori knowledge, including: What is the relevance of the relatively weak noncovalent intramolecular interactions on determining molecular structure, are current hypotheses put forward as to important interactions valid, and how does chemical substitution as various positions along the π-conjugated backbone impact these interactions? How do the intermolecular noncovalent interactions regulate solid-state packing, are there features of the molecular structure – e.g. the π-conjugated backbone, heteroatoms, or pendent alkyl chains – that play a more important role? What connections can be made between the structures/properties of the π-conjugated molecules and the resulting organic semiconductors? In this dissertation, Chapter 1 provides an introductory discussion of these questions and a brief review of previous studies. Chapter 2 details the computational approaches that were implemented throughout the course of the thesis work. Chapter 3 describes the investigation of a series of pyrene-acene molecules to illustrate the importance of choosing the right molecular structure in π-conjugated chromophores. In Chapter 4, S...F noncovalent intramolecular interactions are systematically investigated in two separate cases to highlight the varied impact that these interactions can have on molecular and solid-state packing structures. Chapter 5 describes the investigation of an oscillatory crystal packing structure observed for a series of oligothiophenes that follow the odd-even carbon-atom counts of the pendant alkyl chains. In Chapter 6, the polymorphism of functionalized pentacene molecules is studied to reveal how seemingly simple atomic substitutions can drastically alter solid-state packing. To systematically address the aforementioned fundamental questions, Chapter 7 describes the construction and application of a database of crystalline molecular organic semiconductors. Finally, perspectives regarding future research are provided in Chapter 8