Object-oriented domain specific compilers for programming FPGAs

Published versio

A Reconfigurable Computing Solution to the Parameterized Vertex Cover Problem

Active research has been done in the past two decades in the field of computational intractability. This thesis explores parallel implementations on a RC (reconfigurable computing) platform for FPT (fixed-parameter tractable) algorithms. Reconfigurable hardware implementations of algorithms for solving NP-Complete problems have been of great interest for research in the past few years. However, most of the research that has been done target exact algorithms for solving problems of this nature. Although such implementations have generated good results, it should be kept in mind that the input sizes were small. Moreover, most of these implementations are instance-specific in nature making it mandatory to generate a different circuit for every new problem instance. In this work, we present an efficient and scalable algorithm that breaks out of the conventional instance-specific approach towards a more general parameterized approach to solve such problems. We present approaches based on the theory of fixed-parameter tractability. The prototype problem used as a case study here is the classic vertex cover problem. The hardware implementation has demonstrated speedups of the order of 100x over the software version of the vertex cover problem

Synthesis of FPGA-based accelerators implementing recursive algorithms

Doutoramento em Engenharia InformáticaO desenvolvimento de sistemas computacionais é um processo complexo, com múltiplas etapas, que requer uma análise profunda do problema, levando em consideração as limitações e os requisitos aplicáveis. Tal tarefa envolve a exploração de técnicas alternativas e de algoritmos computacionais para optimizar o sistema e satisfazer os requisitos estabelecidos. Neste contexto, uma das mais importantes etapas é a análise e implementação de algoritmos computacionais. Enormes avanços tecnológicos no âmbito das FPGAs (Field-Programmable Gate Arrays) tornaram possível o desenvolvimento de sistemas de engenharia extremamente complexos. Contudo, o número de transístores disponíveis por chip está a crescer mais rapidamente do que a capacidade que temos para desenvolver sistemas que tirem proveito desse crescimento. Esta limitação já bem conhecida, antes de se revelar com FPGAs, já se verificava com ASICs (Application-Specific Integrated Circuits) e tem vindo a aumentar continuamente. O desenvolvimento de sistemas com base em FPGAs de alta capacidade envolve uma grande variedade de ferramentas, incluindo métodos para a implementação eficiente de algoritmos computacionais. Esta tese pretende proporcionar uma contribuição nesta área, tirando partido da reutilização, do aumento do nível de abstracção e de especificações algorítmicas mais automatizadas e claras. Mais especificamente, é apresentado um estudo que foi levado a cabo no sentido de obter critérios relativos à implementação em hardware de algoritmos recursivos versus iterativos. Depois de serem apresentadas algumas das estratégias para implementar recursividade em hardware mais significativas, descreve-se, em pormenor, um conjunto de algoritmos para resolver problemas de pesquisa combinatória (considerados enquanto exemplos de aplicação). Versões recursivas e iterativas destes algoritmos foram implementados e testados em FPGA. Com base nos resultados obtidos, é feita uma cuidada análise comparativa. Novas ferramentas e técnicas de investigação que foram desenvolvidas no âmbito desta tese são também discutidas e demonstradas.Design of computational systems is a complex multistage process which requires a deep analysis of the problem, taking into account relevant limitations and constraints as well as software/hardware co-design. Such task involves exploring competitive techniques and computational algorithms, enabling the system to be optimized while satisfying given requirements. In this context, one of the most important stages is analysis and implementation of computational algorithms. Tremendous progress in the scope of FPGA (Field-Programmable Gate Array) technology has made it possible to design very complicated engineering systems. However, the number of available transistors grows faster than the ability to meaningfully design with them. This situation is a well known design productivity gap, which was inherited by FPGA from ASIC (Application-Specific Integrated Circuit) and which is increasing continuously. Developing engineering systems on the basis of high capacity FPGAs involves a wide variety of design tools, including methods for efficient implementation of computational algorithms. The thesis is intended to provide a contribution in this area by aiming at reuse, high level abstraction, automation, and clearness of algorithmic specifications. More specifically, it presents research studies which have been carried out in order to obtain criteria regarding implementation of recursive vs. iterative algorithms in hardware. After describing some of the most relevant strategies for implementing recursion in hardware, a selection of algorithms for solving combinatorial search problems (considered as application examples) are also described in detail. Iterative and recursive versions of these algorithms have been implemented and tested in FPGA. Taking into consideration the results obtained, a careful comparative analysis is given. New research-oriented tools and techniques for hardware design which have been developed in the scope of this thesis are also discussed and demonstrated

Solving graph coloring and SAT problems using field programmable gate arrays.

Chu-Keung Chung.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (leaves 88-92).Abstracts in English and Chinese.Abstract --- p.iAcknowledgments --- p.iiiChapter 1 --- Introduction --- p.1Chapter 1.1 --- Motivation and Aims --- p.1Chapter 1.2 --- Contributions --- p.3Chapter 1.3 --- Structure of the Thesis --- p.4Chapter 2 --- Literature Review --- p.6Chapter 2.1 --- Introduction --- p.6Chapter 2.2 --- Complete Algorithms --- p.7Chapter 2.2.1 --- Parallel Checking --- p.7Chapter 2.2.2 --- Mom's --- p.8Chapter 2.2.3 --- Davis-Putnam --- p.9Chapter 2.2.4 --- Nonchronological Backtracking --- p.9Chapter 2.2.5 --- Iterative Logic Array (ILA) --- p.10Chapter 2.3 --- Incomplete Algorithms --- p.11Chapter 2.3.1 --- GENET --- p.11Chapter 2.3.2 --- GSAT --- p.12Chapter 2.4 --- Summary --- p.13Chapter 3 --- Algorithms --- p.14Chapter 3.1 --- Introduction --- p.14Chapter 3.2 --- Tree Search Techniques --- p.14Chapter 3.2.1 --- Depth First Search --- p.15Chapter 3.2.2 --- Forward Checking --- p.16Chapter 3.2.3 --- Davis-Putnam --- p.17Chapter 3.2.4 --- GRASP --- p.19Chapter 3.3 --- Incomplete Algorithms --- p.20Chapter 3.3.1 --- GENET --- p.20Chapter 3.3.2 --- GSAT Algorithm --- p.22Chapter 3.4 --- Summary --- p.23Chapter 4 --- Field Programmable Gate Arrays --- p.24Chapter 4.1 --- Introduction --- p.24Chapter 4.2 --- FPGA --- p.24Chapter 4.2.1 --- Xilinx 4000 series FPGAs --- p.26Chapter 4.2.2 --- Bitstream --- p.31Chapter 4.3 --- Giga Operations Reconfigurable Computing Platform --- p.32Chapter 4.4 --- Annapolis Wildforce PCI board --- p.33Chapter 4.5 --- Summary --- p.35Chapter 5 --- Implementation --- p.36Chapter 5.1 --- Parallel Graph Coloring Machine --- p.36Chapter 5.1.1 --- System Architecture --- p.38Chapter 5.1.2 --- Evaluator --- p.39Chapter 5.1.3 --- Finite State Machine (FSM) --- p.42Chapter 5.1.4 --- Memory --- p.43Chapter 5.1.5 --- Hardware Resources --- p.43Chapter 5.2 --- Serial Graph Coloring Machine --- p.44Chapter 5.2.1 --- System Architecture --- p.44Chapter 5.2.2 --- Input Memory --- p.46Chapter 5.2.3 --- Solution Store --- p.46Chapter 5.2.4 --- Constraint Memory --- p.47Chapter 5.2.5 --- Evaluator --- p.48Chapter 5.2.6 --- Input Mapper --- p.49Chapter 5.2.7 --- Output Memory --- p.49Chapter 5.2.8 --- Backtrack Checker --- p.50Chapter 5.2.9 --- Word Generator --- p.51Chapter 5.2.10 --- State Machine --- p.51Chapter 5.2.11 --- Hardware Resources --- p.54Chapter 5.3 --- Serial Boolean Satisfiability Solver --- p.56Chapter 5.3.1 --- System Architecture --- p.58Chapter 5.3.2 --- Solutions --- p.59Chapter 5.3.3 --- Solution Generator --- p.59Chapter 5.3.4 --- Evaluator --- p.60Chapter 5.3.5 --- AND/OR --- p.62Chapter 5.3.6 --- State Machine --- p.62Chapter 5.3.7 --- Hardware Resources --- p.64Chapter 5.4 --- GSAT Solver --- p.65Chapter 5.4.1 --- System Architecture --- p.65Chapter 5.4.2 --- Variable Memory --- p.65Chapter 5.4.3 --- Flip-Bit Vector --- p.66Chapter 5.4.4 --- Clause Evaluator --- p.67Chapter 5.4.5 --- Adder --- p.70Chapter 5.4.6 --- Random Bit Generator --- p.71Chapter 5.4.7 --- Comparator --- p.71Chapter 5.4.8 --- Sum Register --- p.71Chapter 5.5 --- Summary --- p.71Chapter 6 --- Results --- p.73Chapter 6.1 --- Introduction --- p.73Chapter 6.2 --- Parallel Graph Coloring Machine --- p.73Chapter 6.3 --- Serial Graph Coloring Machine --- p.74Chapter 6.4 --- Serial SAT Solver --- p.74Chapter 6.5 --- GSAT Solver --- p.75Chapter 6.6 --- Summary --- p.76Chapter 7 --- Conclusion --- p.77Chapter 7.1 --- Future Work --- p.78Chapter A --- Software Implementation of Graph Coloring in CHIP --- p.79Chapter B --- Density Improvements Using Xilinx RAM --- p.81Chapter C --- Bit stream Configuration --- p.83Bibliography --- p.88Publications --- p.9

Parallelization of SAT on Reconfigurable Hardware

Quoique très difficile à résoudre, le problème de satisfiabilité Booléenne (SAT) est fréquemment utilisé lors de la modélisation d’applications industrielles. À cet effet, les deux dernières décennies ont vu une progression fulgurante des outils conçus pour trouver des solutions à ce problème NP-complet. Deux grandes avenues générales ont été explorées afin de produire ces outils, notamment l’approche logicielle et matérielle. Afin de raffiner et améliorer ces solveurs, de nombreuses techniques et heuristiques ont été proposées par la communauté de recherche. Le but final de ces outils a été de résoudre des problèmes de taille industrielle, ce qui a été plus ou moins accompli par les solveurs de nature logicielle. Initialement, le but de l’utilisation du matériel reconfigurable a été de produire des solveurs pouvant trouver des solutions plus rapidement que leurs homologues logiciels. Cependant, le niveau de sophistication de ces derniers a augmenté de telle manière qu’ils restent le meilleur choix pour résoudre SAT. Toutefois, les solveurs modernes logiciels n’arrivent toujours pas a trouver des solutions de manière efficace à certaines instances SAT. Le but principal de ce mémoire est d’explorer la résolution du problème SAT dans le contexte du matériel reconfigurable en vue de caractériser les ingrédients nécessaires d’un solveur SAT efficace qui puise sa puissance de calcul dans le parallélisme conféré par une plateforme FPGA. Le prototype parallèle implémenté dans ce travail est capable de se mesurer, en termes de vitesse d’exécution à d’autres solveurs (matériels et logiciels), et ce sans utiliser aucune heuristique. Nous montrons donc que notre approche matérielle présente une option prometteuse vers la résolution d’instances industrielles larges qui sont difficilement abordées par une approche logicielle.Though very difficult to solve, the Boolean satisfiability problem (SAT) is extensively used to model various real-world applications and problems. Over the past two decades, researchers have tried to provide tools that are used, to a certain degree, to find solutions to the Boolean satisfiability problem. The nature of these tools is broadly divided in software and reconfigurable hardware solvers. In addition, the main algorithms used to solve this problem have also been complemented with heuristics of various levels of sophistication to help overcome some of the NP-hardness of the problem. The end goal of these tools has been to provide solutions to industrial-sized problems of enormous size. Initially, reconfigurable hardware tools provided a promising avenue to accelerating SAT solving over traditional software based solutions. However, the level of sophistication of software solvers overcame their hardware counterparts, which remained limited to smaller problem instances. Even so, modern state-of-the-art software solvers still fail unpredictably on some instances. The main focus of this thesis is to explore solving SAT on reconfigurable hardware in order to gain an understanding of what would be essential ingredients to add (and discard) to a very efficient hardware SAT solver that obtains its processing power from the raw parallelism of an FPGA platform. The parallel prototype solver that was implemented in this work has been found to be comparable with other hardware and software solvers in terms of execution speed even though no heuristics or other helping techniques were implemented. We thus show that our approach provides a very promising avenue to solving large, industrial SAT instances that might be difficult to handle by software solvers

ASlib: A Benchmark Library for Algorithm Selection

The task of algorithm selection involves choosing an algorithm from a set of algorithms on a per-instance basis in order to exploit the varying performance of algorithms over a set of instances. The algorithm selection problem is attracting increasing attention from researchers and practitioners in AI. Years of fruitful applications in a number of domains have resulted in a large amount of data, but the community lacks a standard format or repository for this data. This situation makes it difficult to share and compare different approaches effectively, as is done in other, more established fields. It also unnecessarily hinders new researchers who want to work in this area. To address this problem, we introduce a standardized format for representing algorithm selection scenarios and a repository that contains a growing number of data sets from the literature. Our format has been designed to be able to express a wide variety of different scenarios. Demonstrating the breadth and power of our platform, we describe a set of example experiments that build and evaluate algorithm selection models through a common interface. The results display the potential of algorithm selection to achieve significant performance improvements across a broad range of problems and algorithms.Comment: Accepted to be published in Artificial Intelligence Journa

The Parma Polyhedra Library: Toward a Complete Set of Numerical Abstractions for the Analysis and Verification of Hardware and Software Systems

Since its inception as a student project in 2001, initially just for the handling (as the name implies) of convex polyhedra, the Parma Polyhedra Library has been continuously improved and extended by joining scrupulous research on the theoretical foundations of (possibly non-convex) numerical abstractions to a total adherence to the best available practices in software development. Even though it is still not fully mature and functionally complete, the Parma Polyhedra Library already offers a combination of functionality, reliability, usability and performance that is not matched by similar, freely available libraries. In this paper, we present the main features of the current version of the library, emphasizing those that distinguish it from other similar libraries and those that are important for applications in the field of analysis and verification of hardware and software systems.Comment: 38 pages, 2 figures, 3 listings, 3 table

Combining Cubic Dynamical Solvers with Make/Break Heuristics to Solve SAT

Dynamical solvers for combinatorial optimization are usually based on 2superscript{nd} degree polynomial interactions, such as the Ising model. These exhibit high success for problems that map naturally to their formulation. However, SAT requires higher degree of interactions. As such, these quadratic dynamical solvers (QDS) have shown poor solution quality due to excessive auxiliary variables and the resulting increase in search-space complexity. Thus recently, a series of cubic dynamical solver (CDS) models have been proposed for SAT and other problems. We show that such problem-agnostic CDS models still perform poorly on moderate to large problems, thus motivating the need to utilize SAT-specific heuristics. With this insight, our contributions can be summarized into three points. First, we demonstrate that existing make-only heuristics perform poorly on scale-free, industrial-like problems when integrated into CDS. This motivates us to utilize break counts as well. Second, we derive a relationship between make/break and the CDS formulation to efficiently recover break counts. Finally, we utilize this relationship to propose a new make/break heuristic and combine it with a state-of-the-art CDS which is projected to solve SAT problems several orders of magnitude faster than existing software solvers