Clone Detection in Object Oriented Systems

Clone Detection in Object Oriented Systems design gash based Clone Detection in Object Oriented SystemsIshu SinglaRajesh BhatiaAbstract Program gash is an efficient technique for understanding architectural plans by simplifying them. It is a chopine analysis technique that extracts a particular set of statements relevant to any computation. For the last 25 years, the technique has found its application in a subjugate of research areas like testing, debugging, maintenance etc. In this paper, we digest proposed a method to use this technique for bell ringer detection in determination lie designs. As course slicing concentrates only on the relevant portion of the curriculums based upon some criteria, this property idler be utilized in clone detection process. For this we have used Program Dependency Graphs as an intermediate representation. These PDGs are later used to extract isomorphic overtone slices and at long last these slices are matched to let out potential clones .Keywords Partial SlicesPDG Isomorphism.I. IntroductionA code clone represents a sequence of statements that are duplicated in multiple locations of a program. Clones often arise in stemma code as a result of multiple cut paste operations on the source. Thus, Code re-create mountain be considered as the act of copying code fragments and making minor, non-functional alterations in the implemented code. Code cloning increases the maintenance cost because if there is an misunderstanding in the code fragment to be copied, hence that error will be propagated at different places. Thus, the normal functioning of the system is not alter but further development may become prohibitively expensive 12.Pre-processing of the whole program is often not a good choice temporary hookup searching for clones. The program contains a number of irrelevant statements, thus, pre-processing will be a time consuming process 13. Also the approach for finding clones in procedural oriented and endeavor o riented programs is completely different. Clone detection in object oriented programs has a number of problems 15 and sometimes follows different approach.Selecting a particular set of statements from a queen-sized program that contains statements relevant to a particular computation is called program slicing. Thus, Program cut improves program understandability and find its importance in a number of applications such as parcel maintenance, software debugging, testing etc 35.A number of code clone detection techniques have been proposed based on text, token, graphical records, trees and metrics 1. Some other techniques based on models and some hybrid techniques have also been proposed 911. The main advantage of using program slicing is that we can find the non-contiguous, intertwined code clones, where the coder changes some of the statements and the rest of the code remains unchanged in surrounded by24.II. DEFINITIONSProgram slicing was originally introduced by Weiser that defi nes program slicing as an analysis technique which extracts the elements of a program related to a particular computation. That set of statements collectively called as program slice. Program slices contains that parts of a program that affects the values computed at some point of interest. Program slicing automatically decomposes program by determining the entropy and admit dependencies 38.A. SLICING CRITERIONSlicing in program is al managements computed on the basis of some slicing criterion. We can represent slicing criterion as , where S is the statement from which the slice is to be computed and V is the variable for which the slice is to be computed and that variable must exist in the statement S 8.B. data dependenceStatement P is data pendent on statement Q of a program if there exists a variable m at P which is accessed also in statement Q 6. Consider the following example,1.x=102.y=x+cIn statement 1, we are assigning a value 10 to x and in statement 2, we are using the value of x. So, there is a data dependency between the deuce statements 1 and 2.C. CONTROL DEPENDENCYStatement P is control dependent on statement Q if and only if statement P controls the death penalty of statement Q 6. Consider the following example,1.if(statement 1)2. statement 2In the above example, statement 2 will be executed if statement 1 results in true value. Thus, statement 2 is control dependent on statement 1.Figure. 1 flow chart for program slicing based clone detection.III. Clone Detection Using the Program Slicing in object oriented programsFigure 1 shows the flow chart for the clone detection approach. The technique starts by taking two sample java programs. Then, the pre-processing of these programs is to be done, in which we remove the comments and blank spaces. Thereafter, the .class files for the normalized sample programs are generated. After this, the Program Dependency Graphs (PDGs), on the basis of control and data dependencies, are opinionated for the two programs. The program dependency graph is represented in the form of adjacency intercellular substance as shown in figure 2. It is an n*n intercellular substance where n is the no of statements in the normalized program. Every meekness 1 represents the data dependency between the two statements determined from the row and column of the matrix. Similarly, every entry 2 represents the control dependency between two statements.Now, by having a close look at the adjacency matrix, it is quite clear that the matrix is sparse because the situation of zero is higher than the non-zero entries. So comparing the adjacency matrices of the two programs cant be an efficient approach. Thus, an algorithm has been developed that determines the partial slices from the adjacency matrix in the form of lists.In earlier techniques for program slicing, the slicing criterion has to be defined manually to determine the slices. But, in our approach, the program slices are determined automatically on the b asis of the mentioned algorithm. Because, the slices are extracted starting from the first statement, using control and data dependencies in the adjacency matrix.Figure 2. Example of Adjacency matrix obtained from programs.A. Algorithm for Program SlicingInput- A control data dependency adjacency matrix matnn of size n*n where n is the no of statements. Every entry 1 at index matij shows that there is a data dependency between statement i and j and every entry 2 represents the control dependency between statement i and j.Output- Partial slices in form of listsThe partial slices are extracted from the adjacency matrix, which are in the form of lists. Once, the partial slices for the two java programs are determined, we have to match them using an efficient matching algorithm. If there is cloning among the two source codes, then there must be a match between these partial slices. The matching algorithm will find out the extent of cloning between the two programs by comparing the part ial slices and finally return percentage of cloning as result.IV. Related WorkIn last two decades, motley algorithms have been proposed for program slicing. All have its own advantages and shortcomings. In next section, an overview of recent research in the area of program slicing is given.Z. Guangquan et. al proposed a method to slice the concurrent object oriented programs. In this approach the java concurrency model is used and dependencies between the statements are defined. The paper presents the method of extracting slicing criterion from linear temporal logic property and proposes the steps of computing slicing. Multithreaded dependency graph is used for intermediate representation. A Two-pass algorithm based on Variable Cache Table is adapted to compute slices by extracting out the irrelevant portions of the programs. Results show the satisfaction is guaranteed for source and sliced program and the method can be easily extended to handle other concurrency models7.R. Komondo or et. al. proposed a tool to detect clones in C fragments. In their approach, they used program dependence graphs and program slicing to find isomorphic PDG subgraphs. These subgraphs can be represented as clones. This tool is capable of finding non-continuous clones, intertwined clones and clones in which different variable names are used and statements have been reordered. The approach has been applied for the procedural oriented programs and finds many variants of ideal clones. A number of test cases demonstrating the application of approach on large programs have been shown 4.A. Surendran et. al. proposed a partial slicing approach as an effective method of program testing. Partial slices are formed from the combination of static slices and program points. In some cases static slices contains large number of program statements which are of little use in many practical applications. Partial slicing removes the damage of large size of static slices. In their approach they use on ly static slices for the algorithm as static slices give all possible execution paths. As compared to original program there is a significant reduction in the number of statements in static slices using partial slicing. Using the constraints of partial slicing program testing is also simplified. This approach can also be used in debugging, maintenance and finding clones 10.D. Liang et. al. presented system dependence graph for object-oriented softwares. They have shown that their approach is more precise than previous approaches and is more efficient to construct. It distinguishes data members that fit for different objects. It provides a way to represent data members that act as parameters and the effects of polymorphism on parameters and parameter bindings. It presents a concept of object slicing which helps in examine the statements in slice object by object. Object slicing is good technique for debugging and analysis of large scale programs. In their work an efficient mechanism is also provided to represent half(prenominal) programs and to represent classes in class libraries 12.T. Ishio et. al. proposed a program debugging tool. In their approach they proposed dynamic slicing to efficiently topical anaestheticize faults in procedural oriented and object oriented programs. Aspect-oriented programme is used for collecting dynamic information in program slicing calculation. The dynamic data dependence analysis aspect can be woven into various object-oriented programs without changes as the point cuts of the aspect in the approach is made in a generic form. With the help of dynamic program analysis module, a DC slice calculation system is developed. It improves maintainability and reusability of the module. The approach has also a restriction that it does not allow to analyze the local variables and local control structures. The benefits, usability and cost effectiveness of module show that it is a good tool for debugging 13.B. Korel et. al. presents the c oncept of program slicing on the module level which helps in better understanding of program slices of large programs. In this paper on call graph level, execution level and module trace level some(prenominal) static and dynamic program slicing features are proposed. These features can also be used during software maintenance. The concept of static and dynamic program slicing is combined with different methods of visualization which helps in understanding the program. Experiment results show that it helps the process of understanding program 14.V. CONCLUSION AND FUTURE WORKThis paper provides a technique for detecting code clones in object oriented programs. For this purpose, program slicing is used as the base methodology. The algorithm uses PDGs as the intermediate representations for the source program. The PDG is represented in the form of adjacency matrix. Partial slices are extracted from the adjacency matrix and those slices are matched for possible clones.Result shows that program slicing is an efficient way for understanding programs and finding non-contiguous clones and intertwined code clones. The approach uses the control and data dependencies to find out adjacency matrix representation for the PDG. The whole process is automated where the drug user has to interact only once to input the programs for finding clones.Future work involves taking into consideration all the object oriented paradigm. It includes the object oriented programming features such as abstraction, encapsulation, inheritance, and polymorphism. An efficient algorithm for matching partial slices is also to be developed.REFERENCES1 Dhavleesh Rattan, Rajesh Bhatia, Maninder Singh, packet clone detection a systematic review, Information and software technology, Vol. 55, No. 7, pp. 1165-1199, 2013.2 C. K. 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