A Theoretical Approach Involving Recurrence Resolution, Dependence Cycle Statement Ordering and Subroutine Transformation for the Exploitation of Parallelism in Sequential Code.

To exploit parallelism in Fortran code, this dissertation consists of a study of the following three issues: (1) recurrence resolution in Do-loops for vector processing, (2) dependence cycle statement ordering in Do-loops for parallel processing, and (3) sub-routine parallelization. For recurrence resolution, the major findings include: (1) the node splitting algorithm cannot be used directly to break an essential antidependence link, of which the source variable that results in antidependence is itself the sink variable of another true dependence so a correction method is proposed, (2) a sink variable renaming technique is capable of breaking an antidependence and/or output-dependence link, (3) for recurrences formed by only true dependences, a dynamic dependence concept and the derived technique are powerful, and (4) by integrating related techniques, an algorithm for resolving a general multistatement recurrence is developed. The performance of a parallel loop is determined by the level of parallelism and the time delay due to interprocessor communication and synchronization. For a dependence cycle of a single parallel loop executed in a general synchronization mode, the parallelism exposed varies with the alignment of statements. Statements are reordered on the basis of execution-time of the loop as estimated at compile-time. An improved timing formula and a derived statement ordering algorithm are proposed. Further extension of this algorithm to multiple perfectly nested Do-loops with simple global dependence cycle is also presented. The subroutine is a potential source for parallel processing. Several problems must be solved for subroutine parallelization: (1) the precedence of parallel executions of subroutines, (2) identification of the optimum execution mode for each subroutine and (3) the restructuring of a serial program. A five-step approach to parallelize called subroutines for a calling subroutine is proposed: (1) computation of control dependence, (2) approximation of the global effects of subroutines, (3) analysis of data dependence, (4) identification of execution mode, and (5) restructuring of calling and called subroutines. Application of these five steps in a recursive manner to different levels of calling subroutines in a program addresses the parallelization of subroutines

Tools and Algorithms for the Construction and Analysis of Systems

This open access book constitutes the proceedings of the 28th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2022, which was held during April 2-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 46 full papers and 4 short papers presented in this volume were carefully reviewed and selected from 159 submissions. The proceedings also contain 16 tool papers of the affiliated competition SV-Comp and 1 paper consisting of the competition report. TACAS is a forum for researchers, developers, and users interested in rigorously based tools and algorithms for the construction and analysis of systems. The conference aims to bridge the gaps between different communities with this common interest and to support them in their quest to improve the utility, reliability, exibility, and efficiency of tools and algorithms for building computer-controlled systems

Tools and Algorithms for the Construction and Analysis of Systems

This open access book constitutes the proceedings of the 28th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2022, which was held during April 2-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 46 full papers and 4 short papers presented in this volume were carefully reviewed and selected from 159 submissions. The proceedings also contain 16 tool papers of the affiliated competition SV-Comp and 1 paper consisting of the competition report. TACAS is a forum for researchers, developers, and users interested in rigorously based tools and algorithms for the construction and analysis of systems. The conference aims to bridge the gaps between different communities with this common interest and to support them in their quest to improve the utility, reliability, exibility, and efficiency of tools and algorithms for building computer-controlled systems

A Semantics-Based Approach to Optimizing Unstructured Mesh Abstractions

Computational scientists are frequently confronted with a choice: implement algorithms using high-level abstractions, such as matrices and mesh entities, for greater programming productivity or code them using low-level language constructs for greater execution efficiency. We have observed that the cost of implementing a representative unstructured mesh code with high-level abstractions is poor computational intensity---the ratio of floating point operations to memory accesses. Related scientific applications frequently produce little ``science per cycle'' because their abstractions both introduce additional overhead and hinder compiler analysis and subsequent optimization. Our work exploits the semantics of abstractions, as employed in unstructured mesh codes, to overcome these limitations and to guide a series of manual, domain-specific optimizations that significantly improve computational intensity. We propose a framework for the automation of such high-level optimizations within the ROSE source-to-source compiler infrastructure. The specification of optimizations is left to domain experts and library writers who best understand the semantics of their applications and libraries and who are thus best poised to describe their optimization. Our source-to-source approach translates different constructs (e.g., C code written in a procedural style or C++ code written in an object-oriented style) to a procedural form in order to simplify the specification of optimizations. This is accomplished through raising operators, which are specified by a domain expert and are used to project a concrete application from an implementation space to an abstraction space, where optimizations are applied. The transformed code in the abstraction space is then reified as a concrete implementation via lowering operators, which are automatically inferred by inverting the raising operators. Applying optimizations within the abstraction space, rather than the implementation space, leads to greater optimization portability. We use this framework to automate two high-level optimizations. The first uses an inspector/executor approach to avoid costly and redundant traversals of a static mesh by memoizing the relatively few references required to perform the mathematical computations. During the executor phase, the stored entities are accessed directly without resort to the indirection inherent in the original traversal. The second optimization lowers an object-oriented mesh framework, which uses C++ objects to access the mesh and iterate over mesh entities, to a low-level implementation, which uses integer-based access and iteration.Support was provided by a DOE High-Performance Computer Science Fellowship administered by The Krell Institute, Ames, IA

Proceedings of Monterey Workshop 2001 Engineering Automation for Sofware Intensive System Integration

The 2001 Monterey Workshop on Engineering Automation for Software Intensive System Integration was sponsored by the Office of Naval Research, Air Force Office of Scientific Research, Army Research Office and the Defense Advance Research Projects Agency. It is our pleasure to thank the workshop advisory and sponsors for their vision of a principled engineering solution for software and for their many-year tireless effort in supporting a series of workshops to bring everyone together.This workshop is the 8 in a series of International workshops. The workshop was held in Monterey Beach Hotel, Monterey, California during June 18-22, 2001. The general theme of the workshop has been to present and discuss research works that aims at increasing the practical impact of formal methods for software and systems engineering. The particular focus of this workshop was "Engineering Automation for Software Intensive System Integration". Previous workshops have been focused on issues including, "Real-time & Concurrent Systems", "Software Merging and Slicing", "Software Evolution", "Software Architecture", "Requirements Targeting Software" and "Modeling Software System Structures in a fastly moving scenario".Office of Naval ResearchAir Force Office of Scientific Research Army Research OfficeDefense Advanced Research Projects AgencyApproved for public release, distribution unlimite

Working Notes from the 1992 AAAI Spring Symposium on Practical Approaches to Scheduling and Planning

The symposium presented issues involved in the development of scheduling systems that can deal with resource and time limitations. To qualify, a system must be implemented and tested to some degree on non-trivial problems (ideally, on real-world problems). However, a system need not be fully deployed to qualify. Systems that schedule actions in terms of metric time constraints typically represent and reason about an external numeric clock or calendar and can be contrasted with those systems that represent time purely symbolically. The following topics are discussed: integrating planning and scheduling; integrating symbolic goals and numerical utilities; managing uncertainty; incremental rescheduling; managing limited computation time; anytime scheduling and planning algorithms, systems; dependency analysis and schedule reuse; management of schedule and plan execution; and incorporation of discrete event techniques

Behavioral validation in Cyber-physical systems: Safety violations and beyond

The advances in software and hardware technologies in the last two decades have paved the way for the development of complex systems we observe around us. Avionics, automotive, power grid, medical devices, and robotics are a few examples of such systems which are usually termed as Cyber-physical systems (CPS) as they often involve both physical and software components. Deployment of a CPS in a safety critical application mandates that the system operates reliably even in adverse scenarios. While effective in improving confidence in system functionality, testing can not ascertain the absence of failures; whereas, formal verification can be exhaustive but it may not scale well as the system complexity grows. Simulation driven analysis tends to bridge this gap by tapping key system properties from the simulations. Despite their differences, all these analyses can be pivotal in providing system behaviors as the evidence to the satisfaction or violation of a given performance specification. However, less attention has been paid to algorithmically validating and characterizing different behaviors of a CPS. The focus of this thesis is on behavioral validation of Cyber-physical systems, which can supplement an existing CPS analysis framework. This thesis develops algorithmic tools for validating verification artifacts by generating a variety of counterexamples for a safety violation in a linear hybrid system. These counterexamples can serve as performance metrics to evaluate different controllers during design and testing phases. This thesis introduces the notion of complete characterization of a safety violation in a linear system with bounded inputs, and it proposes a sound technique to compute and efficiently represent these characterizations. This thesis further presents neural network based frameworks to perform systematic state space exploration guided by sensitivity or its gradient approximation in learning-enabled control (LEC) systems. The presented technique is accompanied with convergence guarantees and yields considerable performance gain over a widely used falsification platform for a class of signal temporal logic (STL) specifications.Doctor of Philosoph

Fifth NASA Goddard Conference on Mass Storage Systems and Technologies

This document contains copies of those technical papers received in time for publication prior to the Fifth Goddard Conference on Mass Storage Systems and Technologies held September 17 - 19, 1996, at the University of Maryland, University Conference Center in College Park, Maryland. As one of an ongoing series, this conference continues to serve as a unique medium for the exchange of information on topics relating to the ingestion and management of substantial amounts of data and the attendant problems involved. This year's discussion topics include storage architecture, database management, data distribution, file system performance and modeling, and optical recording technology. There will also be a paper on Application Programming Interfaces (API) for a Physical Volume Repository (PVR) defined in Version 5 of the Institute of Electrical and Electronics Engineers (IEEE) Reference Model (RM). In addition, there are papers on specific archives and storage products

Second Conference on Artificial Intelligence for Space Applications

The proceedings of the conference are presented. This second conference on Artificial Intelligence for Space Applications brings together a diversity of scientific and engineering work and is intended to provide an opportunity for those who employ AI methods in space applications to identify common goals and to discuss issues of general interest in the AI community