Stop-list slicing.

Traditional program slicing requires two parameters: a program location and a variable, or perhaps a set of variables, of interest. Stop-list slicing adds a third parameter to the slicing criterion: those variables that are not of interest. This third parameter is called the stoplist. When a variable in the stop-list is encountered, the data-flow dependence analysis of slicing is terminated for that variable. Stop-list slicing further focuses on the computation of interest, while ignoring computations known or determined to be uninteresting. This has the potential to reduce slice size when compared to traditional forms of slicing. In order to assess the size of the reduction obtained via stop-list slicing, the paper reports the results of three empirical evaluations: a large scale empirical study into the maximum slice size reduction that can be achieved when all program variables are on the stop-list; a study on a real program, to determine the reductions that could be obtained in a typical application; and qualitative case-based studies to illustrate stop-list slicing in the small. The large-scale study concerned a suite of 42 programs of approximately 800KLoc in total. Over 600K slices were computed. Using the maximal stoplist reduced the size of the computed slices by about one third on average. The typical program showed a slice size reduction of about one-quarter. The casebased studies indicate that the comprehension effects are worth further consideration

Code extraction algorithms which unify slicing and concept assignment

One approach to reverse engineering is to partially automate subcomponent extraction, improvement and subsequent recombination. Two previously proposed automated techniques for supporting this activity are slicing and concept assignment. However, neither is directly applicable in isolation; slicing criteria (sets of program variables) are simply too low level in many cases, while concept assignment typically fails to produce executable subcomponents. This paper introduces a unification of slicing and concept assignment which exploits their combined advantages, while overcoming their individual weaknesses. Our 'concept slices' are extracted using high level criteria, while producing executable subprograms. The paper introduces three ways of combining slicing, and concept assignment and algorithms for each. The application of the concept slicing algorithms is illustrated with a case study from a large financial organisation

Amorphous procedure extraction

The procedure extraction problem is concerned with the meaning preserving formation of a procedure from a (not necessarily contiguous) selected set of statements. Previous approaches to the problem have used dependence analysis to identify the non-selected statements which must be 'promoted' (also selected) in order to preserve semantics. All previous approaches to the problem have been syntax preserving. This work shows that by allowing transformation of the program's syntax it is possible to extract both procedures and functions in an amorphous manner. That is, although the amorphous extraction process is meaning preserving it is not necessarily syntax preserving. The amorphous approach is advantageous in a variety of situations. These include when it is desirable to avoid promotion, when a value-returning function is to be extracted from a scattered set of assignments to a variable, and when side effects are present in the program from which the procedure is to be extracted

Amorphous procedure extraction

The procedure extraction problem is concerned with the meaning preserving formation of a procedure from a (not necessarily contiguous) selected set of statements. Previous approaches to the problem have used dependence analysis to identify the non-selected statements which must be 'promoted' (also selected) in order to preserve semantics. All previous approaches to the problem have been syntax preserving. This work shows that by allowing transformation of the program's syntax it is possible to extract both procedures and functions in an amorphous manner. That is, although the amorphous extraction process is meaning preserving it is not necessarily syntax preserving. The amorphous approach is advantageous in a variety of situations. These include when it is desirable to avoid promotion, when a value-returning function is to be extracted from a scattered set of assignments to a variable, and when side effects are present in the program from which the procedure is to be extracted

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

CONVENIENCE, ACCESSIBILITY, AND THE DEMAND FOR FAST FOOD

This study explores the growth in demand for fast food. A distinguishing characteristic of fast food is its convenience; in today's pervasive marketplace, consumers need not travel far to find a fast food outlet. This greater availability translates into a decrease in the full price of obtaining a meal, which contributes to greater consumption. Market-level data are used to estimate demand equations in two time periods, incorporating changes in availability as well as prices, income, and various demographic characteristics. Our findings show that greater availability has led to increased consumption. Failure to account for these types of marketplace changes could lead to incorrect inferences regarding the factors responsible for the industry growth.Demand and Price Analysis,

An empirical study of computation equivalence as determined by decomposition slice equivalence.

In order to further understand and assess decomposition slicing we characterize and evaluate the size of reductions obtained by computing equivalent decomposition slices from the perspective of the comprehender, maintainer, tester and researcher. The analysis was performed on 68 C language systems of sizes 100 to 50,000 lines. All decomposition slices were computed and compared for simple equality. From this data, we were able to determine with 95% confidence that the true mean percentage of equivalent decomposition slices is between 50.0% and 60.3%, with a p-value < 0.005. This has clear and significant impact for software testing, as any coverage method used for one of the variables used in an equivalence will apply to all variables in the class; for software comprehension as the number of items (variables) used for the understander is substantially reduced; for the software maintenance, as the number computational relationships is reduced; and for the researcher, in attempting to ascertain the underlying cause of this phenomena

The Impact of Demographics, Market Characteristics, and Prices on the Consumption of Food-Away-From-Home

Food Consumption/Nutrition/Food Safety,