Object-oriented program animation using JAN

Concept and design of the program animation system JAN are described. JAN visualizes the execution of a Java program by dynamically unfolding an object diagram and an interaction diagram. Several features distinguish JAN from existing program visualization systems and visual debuggers. Annotations in the program code can be used to control the animation by selecting the relevant events and customizing the visual appearance. In addition, the user can interactively steer the animation in various ways. JAN is an integrated visualization system which includes an elaborate graphical user interface, a preprocessor for annotated Java source code and a visualization engine that runs in a separate Java virtual machine. The design of the system is described in detail

An efficient and generic reversible debugger using the virtual machine based approach

The reverse execution of programs is a function where pro-grams are executed backward in time. A reversible debugger is a debugger that provides such a functionality. In this pa-per, we propose a novel reversible debugger that enables reverse execution of programs written in the C language. Our approach takes the virtual machine based approach. In this approach, the target program is executed on a special virtual machine. Our contribution in this paper is two-fold. First, we propose an approach that can address problems of (1) compatibility and (2) efficiency that exist in previous works. By compatibility, we mean that previous debuggers are not generic, i.e., they support only a special language or special intermediate code. Second, our approach provides two execution modes: the native mode, where the debuggee is directly executed on a real CPU, and the virtual ma-chine mode, where the debuggee is executed on a virtual machine. Currently, our debugger provides four types of trade-off settings (designated by unit and optimization) to consider trade-offs between granularity, accuracy, overhead and memory requirement. The user can choose the appro-priate setting flexibly during debugging without finishing and restarting the debuggee

Explainable Automated Debugging via Large Language Model-driven Scientific Debugging

Automated debugging techniques have the potential to reduce developer effort in debugging, and have matured enough to be adopted by industry. However, one critical issue with existing techniques is that, while developers want rationales for the provided automatic debugging results, existing techniques are ill-suited to provide them, as their deduction process differs significantly from that of human developers. Inspired by the way developers interact with code when debugging, we propose Automated Scientific Debugging (AutoSD), a technique that given buggy code and a bug-revealing test, prompts large language models to automatically generate hypotheses, uses debuggers to actively interact with buggy code, and thus automatically reach conclusions prior to patch generation. By aligning the reasoning of automated debugging more closely with that of human developers, we aim to produce intelligible explanations of how a specific patch has been generated, with the hope that the explanation will lead to more efficient and accurate developer decisions. Our empirical analysis on three program repair benchmarks shows that AutoSD performs competitively with other program repair baselines, and that it can indicate when it is confident in its results. Furthermore, we perform a human study with 20 participants, including six professional developers, to evaluate the utility of explanations from AutoSD. Participants with access to explanations could judge patch correctness in roughly the same time as those without, but their accuracy improved for five out of six real-world bugs studied: 70% of participants answered that they wanted explanations when using repair tools, while 55% answered that they were satisfied with the Scientific Debugging presentation

Proceedings of the Second Program Visualization Workshop, 2002

The Program Visualization Workshops aim to bring together researchers who design and construct program visualizations and, above all, educators who use and evaluate visualizations in their teaching. The first workshop took place in July 2000 at Porvoo, Finland. The second workshop was held in cooperation with ACM SIGCSE and took place at HornstrupCentret, Denmark in June 2002, immediately following the ITiCSE 2002 Conference in Aarhus, Denmark

Modular average case analysis: Language implementation and extension

Motivated by accurate average-case analysis, MOdular Quantitative Analysis (MOQA) is developed at the Centre for Efficiency Oriented Languages (CEOL). In essence, MOQA allows the programmer to determine the average running time of a broad class of programmes directly from the code in a (semi-)automated way. The MOQA approach has the property of randomness preservation which means that applying any operation to a random structure, results in an output isomorphic to one or more random structures, which is key to systematic timing. Based on original MOQA research, we discuss the design and implementation of a new domain specific scripting language based on randomness preserving operations and random structures. It is designed to facilitate compositional timing by systematically tracking the distributions of inputs and outputs. The notion of a labelled partial order (LPO) is the basic data type in the language. The programmer uses built-in MOQA operations together with restricted control flow statements to design MOQA programs. This MOQA language is formally specified both syntactically and semantically in this thesis. A practical language interpreter implementation is provided and discussed. By analysing new algorithms and data restructuring operations, we demonstrate the wide applicability of the MOQA approach. Also we extend MOQA theory to a number of other domains besides average-case analysis. We show the strong connection between MOQA and parallel computing, reversible computing and data entropy analysis

Distributed workflows with Jupyter

The designers of a new coordination interface enacting complex workflows have to tackle a dichotomy: choosing a language-independent or language-dependent approach. Language-independent approaches decouple workflow models from the host code's business logic and advocate portability. Language-dependent approaches foster flexibility and performance by adopting the same host language for business and coordination code. Jupyter Notebooks, with their capability to describe both imperative and declarative code in a unique format, allow taking the best of the two approaches, maintaining a clear separation between application and coordination layers but still providing a unified interface to both aspects. We advocate the Jupyter Notebooks’ potential to express complex distributed workflows, identifying the general requirements for a Jupyter-based Workflow Management System (WMS) and introducing a proof-of-concept portable implementation working on hybrid Cloud-HPC infrastructures. As a byproduct, we extended the vanilla IPython kernel with workflow-based parallel and distributed execution capabilities. The proposed Jupyter-workflow (Jw) system is evaluated on common scenarios for High Performance Computing (HPC) and Cloud, showing its potential in lowering the barriers between prototypical Notebooks and production-ready implementations

A strip-like tiling algorithm

AbstractWe extend our previous results on the connection between strip tiling problems and regular grammars by showing that an analogous algorithm is applicable to other tiling problems, not necessarily related to rectangular strips. We find generating functions for monomer and dimer tilings of T- and L-shaped figures, holed and slotted strips, diagonal strips and combinations of them, and show how analogous results can be obtained by using different pieces

Kolmogorov Complexity in perspective. Part II: Classification, Information Processing and Duality

We survey diverse approaches to the notion of information: from Shannon entropy to Kolmogorov complexity. Two of the main applications of Kolmogorov complexity are presented: randomness and classification. The survey is divided in two parts published in a same volume. Part II is dedicated to the relation between logic and information system, within the scope of Kolmogorov algorithmic information theory. We present a recent application of Kolmogorov complexity: classification using compression, an idea with provocative implementation by authors such as Bennett, Vitanyi and Cilibrasi. This stresses how Kolmogorov complexity, besides being a foundation to randomness, is also related to classification. Another approach to classification is also considered: the so-called "Google classification". It uses another original and attractive idea which is connected to the classification using compression and to Kolmogorov complexity from a conceptual point of view. We present and unify these different approaches to classification in terms of Bottom-Up versus Top-Down operational modes, of which we point the fundamental principles and the underlying duality. We look at the way these two dual modes are used in different approaches to information system, particularly the relational model for database introduced by Codd in the 70's. This allows to point out diverse forms of a fundamental duality. These operational modes are also reinterpreted in the context of the comprehension schema of axiomatic set theory ZF. This leads us to develop how Kolmogorov's complexity is linked to intensionality, abstraction, classification and information system.Comment: 43 page

A new approach to reversible computing with applications to speculative parallel simulation

In this thesis, we propose an innovative approach to reversible computing that shifts the focus from the operations to the memory outcome of a generic program. This choice allows us to overcome some typical challenges of "plain" reversible computing. Our methodology is to instrument a generic application with the help of an instrumentation tool, namely Hijacker, which we have redesigned and developed for the purpose. Through compile-time instrumentation, we enhance the program's code to keep track of the memory trace it produces until the end. Regardless of the complexity behind the generation of each computational step of the program, we can build inverse machine instructions just by inspecting the instruction that is attempting to write some value to memory. Therefore from this information, we craft an ad-hoc instruction that conveys this old value and the knowledge of where to replace it. This instruction will become part of a more comprehensive structure, namely the reverse window. Through this structure, we have sufficient information to cancel all the updates done by the generic program during its execution. In this writing, we will discuss the structure of the reverse window, as the building block for the whole reversing framework we designed and finally realized. Albeit we settle our solution in the specific context of the parallel discrete event simulation (PDES) adopting the Time Warp synchronization protocol, this framework paves the way for further general-purpose development and employment. We also present two additional innovative contributions coming from our innovative reversibility approach, both of them still embrace traditional state saving-based rollback strategy. The first contribution aims to harness the advantages of both the possible approaches. We implement the rollback operation combining state saving together with our reversible support through a mathematical model. This model enables the system to choose in autonomicity the best rollback strategy, by the mutable runtime dynamics of programs. The second contribution explores an orthogonal direction, still related to reversible computing aspects. In particular, we will address the problem of reversing shared libraries. Indeed, leading from their nature, shared objects are visible to the whole system and so does every possible external modification of their code. As a consequence, it is not possible to instrument them without affecting other unaware applications. We propose a different method to deal with the instrumentation of shared objects. All our innovative proposals have been assessed using the last generation of the open source ROOT-Sim PDES platform, where we integrated our solutions. ROOT-Sim is a C-based package implementing a general purpose simulation environment based on the Time Warp synchronization protocol