Execution replay and debugging

As most parallel and distributed programs are internally non-deterministic -- consecutive runs with the same input might result in a different program flow -- vanilla cyclic debugging techniques as such are useless. In order to use cyclic debugging tools, we need a tool that records information about an execution so that it can be replayed for debugging. Because recording information interferes with the execution, we must limit the amount of information and keep the processing of the information fast. This paper contains a survey of existing execution replay techniques and tools.Comment: In M. Ducasse (ed), proceedings of the Fourth International Workshop on Automated Debugging (AADebug 2000), August 2000, Munich. cs.SE/001003

A high-order language for a system of closely coupled processing elements

The research reported in this paper was occasioned by the requirements on part of the Real-Time Digital Simulator (RTDS) project under way at NASA Lewis Research Center. The RTDS simulation scheme employs a network of CPUs running lock-step cycles in the parallel computations of jet airplane simulations. Their need for a high order language (HOL) that would allow non-experts to write simulation applications and that could be implemented on a possibly varying network can best be fulfilled by using the programming language Ada. We describe how the simulation problems can be modeled in Ada, how to map a single, multi-processing Ada program into code for individual processors, regardless of network reconfiguration, and why some Ada language features are particulary well-suited to network simulations

Development and Specification of Virtual Environments

This thesis concerns the issues involved in the development of virtual environments (VEs). VEs are more than virtual reality. We identify four main characteristics of them: graphical interaction, multimodality, interface agents, and multi-user. These characteristics are illustrated with an overview of different classes of VE-like applications, and a number of state-of-the-art VEs. To further define the topic of research, we propose a general framework for VE systems development, in which we identify five major classes of development tools: methodology, guidelines, design specification, analysis, and development environments. Of each, we give an overview of existing best practices

The Do-loop Considered Harmful in Production System Programming

In this paper we focus on some aspects of Expert System programming. In particular we consider some of the language constructs which from part of a new production system language known as Herbal that we are developing at Columbia University. These language constructs greatly increase the expressiveness of a typical production system language and can be efficiently executed on a para11el machine. We briefly describe the DADO machine under development at Columbia University and J basic algorithm for production system execution for that machine. We conclude with a discussion of some performance Statistics recently calculated from m _analysis of production systems simulations and describe the expected effects of our added language constructs on these statistics

Information Flow Analysis for Detecting Non-Determinism in Blockchain

A mandatory feature for blockchain software, such as smart contracts and decentralized applications, is determinism. In fact, non-deterministic behaviors do not allow blockchain nodes to reach one common consensual state or a deterministic response, which causes the blockchain to be forked, stopped, or to deny services. While domain-specific languages are deterministic by design, general purpose languages widely used for the development of smart contracts such as Go, provide many sources of non-determinism. However, not all non-deterministic behaviours are critical. In fact, only those that affect the state or the response of the blockchain can cause problems, as other uses (for example, logging) are only observable by the node that executes the application and not by others. Therefore, some frameworks for blockchains, such as Hyperledger Fabric or Cosmos SDK, do not prohibit the use of non-deterministic constructs but leave the programmer the burden of ensuring that the blockchain application is deterministic. In this paper, we present a flow-based approach to detect non-deterministic vulnerabilities which could compromise the blockchain. The analysis is implemented in GoLiSA, a semantics-based static analyzer for Go applications. Our experimental results show that GoLiSA is able to detect all vulnerabilities related to non-determinism on a significant set of applications, with better results than other open-source analyzers for blockchain software written in Go