Search-based amorphous slicing

Amorphous slicing is an automated source code extraction technique with applications in many areas of software engineering, including comprehension, reuse, testing and reverse engineering. Algorithms for syntax-preserving slicing are well established, but amorphous slicing is harder because it requires arbitrary transformation; finding good general purpose amorphous slicing algorithms therefore remains as hard as general program transformation. In this paper we show how amorphous slices can be computed using search techniques. The paper presents results from a set of experiments designed to explore the application of genetic algorithms, hill climbing, random search and systematic search to a set of six subject programs. As a benchmark, the results are compared to those from an existing analytical algorithm for amorphous slicing, which was written specifically to perform well with the sorts of program under consideration. The results, while tentative at this stage, do give grounds for optimism. The search techniques proved able to reduce the size of the programs under consideration in all cases, sometimes equaling the performance of the specifically-tailored analytic algorithm. In one case, the search techniques performed better, highlighting a fault in the existing algorith

Program simplification as a means of approximating undecidable propositions

We describe an approach which mixes testing, slicing, transformation and formal verification to investigate speculative hypotheses concerning a program, formulated during program comprehension activity. Our philosophy is that such hypotheses (which are typically undecidable) can, in some sense, be `answered' by a partly automated system which returns neither `true' nor `false' but a program (the `test program') which computes the answer. The motivation for this philosophy is the way in which, as we demonstrate, static analysis and manipulation technology can be applied to ensure that the resulting test program is significantly simpler than the original program, thereby simplifying the process of investigating the original hypothesi

Loop squashing transformations for amorphous slicing

Program slicing is a source code extraction technique that can be used to support reverse engineering by automatically extracting executable subprograms that preserve some aspect of the original program's semantics. Although minimal slices are not generally computable, safe approximate algorithms can be used to good effect. However, the precision of such slicing algorithms is a major factor in determining the value of slicing for reverse engineering. Amorphous slicing has been proposed as a way of reducing the size of a slice. Amorphous slices preserve the aspect of semantic interest, but not the syntax that denotes it, making them generally smaller than their syntactically restricted counterparts. Amorphous slicing is suitable for many reverse engineering applications, since reverse engineering typically abandons the existing syntax to facilitate structural improvements. Previous work on amorphous slicing has not attempted to exploit its potential to apply loop-squashing transformations. This paper presents an algorithm for amorphous slicing of loops, which identifies induction variables, transformation rule templates and iteration-determining compile-time expressions. The algorithm uses these to squash certain loops into conditional assignments. The paper also presents an inductive proof of the rule templates and illustrates the application of the algorithm with a detailed example of loop squashing

A Graph Coloring Approach to Dynamic Slicing of Object-Oriented Programs

Program slicing is a decomposition technique, which produces a subprogram from the parent program relevant to a particular computation. Hence slicing is also regarded as a program transformation technique. A dynamic program slice is an executable part of a program whose behavior is identical, for the same program input, to that of the original program with respect to a variable of interest at some execution position. Dynamic slices are smaller than static slice, which can be used eciently in dierent software engineering activities like program testing, debugging, software maintenance, program comprehension etc. In this dissertation, we present our work concerned with the dynamic slicing of object-oriented programs. We have developed a novel algorithm, which incorporates graph coloring technique to compute dynamic slice of object-oriented programs. But in order to achieve the goal efficiently, we have contradicted the constraints of the traditional graph coloring theory. Moreover, the state restriction of the slicing criterion is taken into consideration, in addition to the dependence analysis. The advantage of our algorithm is that, it is more time ecient than the existing algorithms. We have named this algorithm, as Contradictory Graph Coloring Algorithm (CGCA)

Enhancing the performance of Decoupled Software Pipeline through Backward Slicing

The rapidly increasing number of cores available in multicore processors does not necessarily lead directly to a commensurate increase in performance: programs written in conventional languages, such as C, need careful restructuring, preferably automatically, before the benefits can be observed in improved run-times. Even then, much depends upon the intrinsic capacity of the original program for concurrent execution. The subject of this paper is the performance gains from the combined effect of the complementary techniques of the Decoupled Software Pipeline (DSWP) and (backward) slicing. DSWP extracts threadlevel parallelism from the body of a loop by breaking it into stages which are then executed pipeline style: in effect cutting across the control chain. Slicing, on the other hand, cuts the program along the control chain, teasing out finer threads that depend on different variables (or locations). parts that depend on different variables. The main contribution of this paper is to demonstrate that the application of DSWP, followed by slicing offers notable improvements over DSWP alone, especially when there is a loop-carried dependence that prevents the application of the simpler DOALL optimization. Experimental results show an improvement of a factor of ?1.6 for DSWP + slicing over DSWP alone and a factor of ?2.4 for DSWP + slicing over the original sequential code

Safe Concurrency Introduction through Slicing

Traditional refactoring is about modifying the structure of existing code without changing its behaviour, but with the aim of making code easier to understand, modify, or reuse. In this paper, we introduce three novel refactorings for retrofitting concurrency to Erlang applications, and demonstrate how the use of program slicing makes the automation of these refactorings possible

Program Transformations for Information Personalization

Personalization constitutes the mechanisms necessary to automatically customize information content, structure, and presentation to the end user to reduce information overload. Unlike traditional approaches to personalization, the central theme of our approach is to model a website as a program and conduct website transformation for personalization by program transformation (e.g., partial evaluation, program slicing). The goal of this paper is study personalization through a program transformation lens and develop a formal model, based on program transformations, for personalized interaction with hierarchical hypermedia. The specific research issues addressed involve identifying and developing program representations and transformations suitable for classes of hierarchical hypermedia and providing supplemental interactions for improving the personalized experience. The primary form of personalization discussed is out-of-turn interaction—a technique that empowers a user navigating a hierarchical website to postpone clicking on any of the hyperlinks presented on the current page and, instead, communicate the label of a hyperlink nested deeper in the hierarchy. When the user supplies out-of-turn input, we personalize the hierarchy to reflect the user\u27s informational need. While viewing a website as a program and site transformation as program transformation is non-traditional, it offers a new way of thinking about personalized interaction, especially with hierarchical hypermedia. Our use of program transformations casts personalization in a formal setting and provides a systematic and implementation-neutral approach to designing systems. Moreover, this approach helped connect our work to human-computer dialog management and, in particular, mixed-initiative interaction. Putting personalized web interaction on a fundamentally different landscape gave birth to this new line of research. Relating concepts in the web domain (e.g., sites, interactions) to notions in the program-theoretic domain (e.g., programs, transformations) constitutes the creativity in this work

Forward Slicing by Conjunctive Partial Deduction and Argument Filtering

Program slicing is a well-known methodology that aims at identifying the program statements that (potentially) affect the values computed at some point of interest. Within imperative programming, this technique has been successfully applied to debugging, specialization, merging, reuse, maintenance, etc. Due to its declarative nature, adapting the slicing notions and techniques to a logic programming setting is not an easy task. In this work, we define the first, semantics-preserving, forward slicing technique for logic programs. Our approach relies on the application of a conjunctive partial deduction algorithm for a precise propagation of information between calls. We do not distinguish between static and dynamic slicing since partial deduction can naturally deal with both static and dynamic data. Furthermore, this approach can quite easily be implemented by adding a new code generator on top of existing partial deduction systems. A slicing tool has been implemented in ECCE, where a post-processing transformation to remove redundant arguments has been added. Experiments conducted on a wide variety of programs are encouraging and demonstrate the usefulness of our approach, both as a classical slicing method and as a technique for code size reduction