MICEI Braga Portugal Strategies to relate the program

MICEI Braga – Portugal Strategies to relate the program and problem domains using code instrumentation Mario Marcelo Berón University of Minho Pedro Rangel Henriques University of Minho Maria João Varanda Pereira Polytechnic Institute of Bragança MICEI-University of Minho Roberto Uzal University of San Luis

Motivation In the context of PCVIA, we want to explore and implement code inspection approaches and tools for Program Comprehension activities. We will give special attention to approaches that support the mapping between behavioral and operational views of programs. We will present a code instrumentation based strategy. MICEI-University of Minho

Topics Program Comprehension: concepts and tools Program Comprehension Approach Strategy to relate different views Case Study: EAR (Un Evaluador de Algoritmos de Ruteo) • Conclusion • Future Work • • MICEI-University of Minho

Program Comprehension Concept and tools Program Comprehension Software Engineering discipline which aims at understanding computer code written in a high-level programming language. Program Comprehension is useful for reuse, maintenance, reverse engineering and many other activities in the context of Software Engineering. MICEI-University of Minho

Program Comprehension Concept and tools Program Comprehension Tool A program that aims at making the understanding of a software application easier, through the presentation of different perspectives (views) of the overall system or its components. MICEI-University of Minho

Program Comprehension Concept and tools A PC Tool has modules to: • Extract information by parsing the source code • Store and handle the information extracted • Visualize all the retrieved information MICEI-University of Minho

Program Comprehension Concepts and tools General purpose • Eclipse SDK • Visual Studio. Net Domain specific • SHri. MP • Creole • Jeliot 3 • Imagix 4 D • Codesurfer MICEI-University of Minho

Program Comprehension Concepts and tools Views: System representations that help the user to understand the systems under analysis Interesting Views • Machine (ex. Byte Code, Assembly Code) • Program (ex. C code, Java code) • Functions and data used in runtime • Function Graph • Module Graph • Effect on the problem domain (behavioral) MICEI-University of Minho

Program Comprehension Concepts and tools MICEI-University of Minho

Topics Program Comprehension: concepts and tools Program Comprehension Approach Strategy to relate different views Case Study: EAR (Un Evaluador de Algoritmos de Ruteo) • Conclusion • Future Work • • MICEI-University of Minho

Code Inspection by Instrumentation Consists in the insertion of useful statements into the source code to get runtime (dynamic) information that allows us to follow program execution. MICEI-University of Minho

Code Inspection by Instrumentation: • Inspector Function: inserted at check points (begin and end of functions). • Iteration Control Statements: inserted before inside and after cyclic statements. MICEI-University of Minho

Code Inspection by Instrumentation Function Handling int f (int x, int y) { { float z, k; /* more declarations*/ INPUT_INSPECTOR(“f”); ……… /* actions */ return value; OUTPUT_INSPECTOR(“f”); } return value; } MICEI-University of Minho

Code Inspection by Instrumentation Function Handling {1 for (initialization; condition; action) for(initialization, condition, action) { actions; 2 1. push(s, number. Of. Times) 2. v=pop(s); v=v-1; push(s, v) 3. pop(s) } 3 } MICEI-University of Minho

Code Inspection by Instrumentation Data Handling int a; int f (int x, int y) { float z, k; data /* more declarations*/ INPUT_INSPECTOR(“f”, data); ……… /* actions */ OUTPUT_INSPECTOR(“f”, data); return value; } MICEI-University of Minho

Code Inspection by Instrumentation Data Handling long int (*f([][])(int, int (float *[], int []); MICEI-University of Minho

Topics Program Comprehension: concept and tools Program Comprehension Approach Strategy to relate different views Case Study: EAR (Un Evaluador de Algoritmos de Ruteo) • Conclusion • Future Work • • MICEI-University of Minho

Relationship between Views The relationship between different levels of the architecture can be made using the information available in the information repository. The problem appear when we want to relate the Operational and Behavioral views. In this case we can use BORS. MICEI-University of Minho

BORS Behavioral-Operational Relation Strategy Behavioral View Operational View Used Functions to build the output Program Output ? The used functions to build the output are known but: What about each object in the problem domain? Is it possible to recover the functions used to build each object? MICEI-University of Minho

BORS Behavioral-Operational Relation Strategy Behavioral View Operational View Program Output Used Functions to build the output ! Objects + Interface Nodes Node Functions Arc Functions. . . . Function execution tree MICEI-University of Minho

BORS Procedure 1. Detect the functions related with each Problem Domain Object. 2. Build an fe-tree (Functions Execution Tree) with the used functions in runtime. 3. Explain the functions found in step 1 using the tree built in step 2. MICEI-University of Minho

BORS: Step 1 Detecting the functions related with the domain objects The Grep technique allow us to get all the functions related (by name) with an object (syntactic matching). The programmer must analyze if the recovered functions are semantically related with the object under consideration. Important: This process would be easier if the system under study was implemented using Abstract Data Types. MICEI-University of Minho

BORS: Step 2 Build a fe-Tree The functions used at runtime to build the output can be obtained through source code instrumentation. Our annotation scheme inserts “inspector functions” at the beginning and at the end of each functions present in the source code. With these information we can build a tree denominated fe-Tree. MICEI-University of Minho

BORS: Step 3 Explain the functions using the fe-tree MICEI-University of Minho

Topics Program Comprehension: concept and tools Program Comprehension Approach Strategy to relate different views Case Study: EAR (Un Evaluador de Algoritmos de Ruteo) • Conclusion • Future Work • • MICEI-University of Minho

Program Comprehension Concepts and tools EAR: Integrated Environment MICEI-University of Minho

Program Comprehension Concepts and tools Function Graph of EAR MICEI-University of Minho

Program Comprehension Concepts and tools Module Graph of EAR System MICEI-University of Minho

Program Comprehension Concepts and tools Function Graph of Morelia Module MICEI-University of Minho

Case Study EAR: Module Graph MICEI-University of Minho

Case Study EAR: Function Graph by Module with different abstraction levels MICEI-University of Minho

Case Study EAR: BORS applied to plannar graph MICEI-University of Minho

Topics Program Comprehension: concept and tools Program Comprehension Approach Strategy to relate different views Case Study: EAR (Un Evaluador de Algoritmos de Ruteo) • Conclusion • Future Work • • MICEI-University of Minho

Conclusions The use of inspector functions (IF), weaved into the source code, allows us to capture the actual flow of the functions during execution. To control the size of the output list of functions generated by the inpection, we adopted a suitable strategy based on the weaving of iteration control statements (ICS). Both IF and ICS were inserted into the source code in a systematic instrumentation strategy that could be done automatically. MICEI-University of Minho

Conclusions With our approach we can obtain many different views of EAR, very useful to study and understand the system. Statcis: • Assembly code • Source code • Function graph • Module graph Dynamics: • Runtime functions • Trace to module level • Trace to function level MICEI-University of Minho

Conclusions BORS is useful to relate the behavioral and operational views and to create a true aid for Program Comprehension. BORS can be totally automatized if the programming paradigm is object oriented. MICEI-University of Minho

Topics Program Comprehension: concept and tools Program Comprehension Approach Strategy to relate different views Case Study: EAR (Un Evaluador de Algoritmos de Ruteo) • Conclusion • Future Work • • MICEI-University of Minho

Future Work It is necessary to develop a more robust data structure to handle the recovered information from our instrumentation scheme. To develop strategies to decorate the algorithms output. In other words to show the behavioral-operational relation explicitly. To implement metrics to help the programmer to select the input for BORS. MICEI-University of Minho

Future Work To identify the domain objects. To assess our tool, collecting experimental indicators about its use for program understanding. MICEI-University of Minho

Thanks you for your attention Mario M. Berón Pedro Rangel Santos Henriques Maria João Varanda Pereira Roberto Uzal MICEI-University of Minho