Selected Topics of Software Technology 3 Repair & … Topics of Software Technology 3 2 Refactoring...

Selected Topics of Software Technology 3

Refactoring and Repair1

S C I E N C E P A S S I O N T E C H N O L O G Y

u www.tugraz.at


Repair & Refactoring

Birgit Hofer

Institute for Software Technology



Outline

Model-based Software Debugging

o Traffic Light Example

Repair

o Genetic programming

o Software (C, Java)

o Spreadsheets

Refactoring

Exam



Outline



Repair



o Spreadsheets

Refactoring

Exam



Traffic Light Example1. public static void test () {

2. TrafficLight tl = new TrafficLight(0); // initializes tl.state=0;

3. int i = 0;

4. int finalState;

5. while (i < 5) {

6. tl.printState();

7. if (tl.state == 0) {

8. tl.state = 1;

9. } else {

10. if (tl.state == 1) {

11. tl.state = 2;

12. } else {

13. if (tl.state == 2) {

14. tl.state = 3;

15. } else {

16. tl.state = 3; // should be tl.state = 0;

17. }

18. }

19. }

20. i++;

21. }

22. tl.printState();

23. finalState = tl.state;

24. }



Traffic Light Example – Hints for the solution

#FACTS

eq(not_intrace_0,0) # initialization

eq(finalState_0,1) # expected output value

eq(state_0,0) # input

Intrace variables

WHILEs are control-dependent of the previous WHILE

The IF in Line 7 is control-dependent on the previous WHILE

Each other IF is control-dependent on the previous IF.

Lines 8/11/12/16 are control-dependent on the previous IF

Line 20 is control-dependent on the previous WHILE

Line 23 is control-dependent on intrace_0.



Traffic Light Example

How many single fault solutions do you get?

Do you get a solution if you set the watchsumgeq/leg of the AB

variables to 0?

Would it help if you add more facts to the constraints system, e.g.

state_2=2?



Outline



Repair



o Spreadsheets

Refactoring

Exam



Fault localization

Spectrum-based

Model-based

Repair Genetic

Spreadsheet

Quality Assurance

Techniques

Visualization

Static Analysis

Debugging

Testing

Modeling

Design & Maintenance

Support

Source: Jannach et al. “Avoiding, Finding and Fixing Spreadsheet Errors – A Survey of

Automated Approaches for Spreadsheet QA”, in Journal of Systems and Software, 2014.

Visualization: Patrick Koch,Diploma Seminar, TU Graz, 2015.

Debugging

Genetic



Evolutionary methodology to find computer

programs that perform a user-defined task

Genetic Programming



Principles of Genetic Programming (GP)

Evolution

Mutation

Cross-over

Survival of the fittest

Fitness function, e.g., test cases



Program Representation in GP

+

- *

/8

x

y

2

-

3

8 – x / 2 + y * (-3)



Mutation

+

- *

/8

x

y

2

-

3

8 – x / 2 + y * (-3)

+

8 + x / 2 + y * (-3)



Crossover 1

+

- *

8 y/

x 2

-

3

8 – x / 2 + y * (-3)

/

x 2

8 – x / 2 + y * x / 2



Crossover 2

-

/8

x 2

-

3x

Mutant 1 Mutant 2

/

x 2



Crossover 3 – Crossing back

-

/8

x 2

-

3x

Original program Mutant

/

x 2



Genetic Programming - Workflow

Source: Patrick W. Koch: “Framework for Automated Spreadsheet Debugging conducting Evolutionary Strategies”, Master-Project, 2013.



Outline



Repair



o Spreadsheets

Refactoring

Exam



Genetic Programming For Automated Software Repair

Faulty

program

Test cases

AST

(abstract

syntax tree)

Copy1Copy2Copy1Copyn

Copy1Copy2Copy1Mutantn

Evaluation

(Fitness)

Elimination

Copy1Mutantn

Source: Forrest et al.: “A Genetic Programming Approach to Automated Software Repair”, GECCO, 2009.



Genetic Programming For Automated Software Repair

Faulty

program

Test cases

AST

(abstract

syntax tree)

Copy1Copy2Copy1Copyn

Copy1Copy2Copy1Mutantn

Evaluation

(Fitness)

Elimination

Copy1Mutantn


Minimized

Solution



Smart statement selection for mutation

Weighted pathStatement visited by

Negative TC 1.0

Positive and negative TC 0.1

Positive TC 0.0

Finer-grained selection possible

Do you have ideas for a finer selection?



Mutation operators

Delete statement

Insert statement

Swap statements



GCD Example

Source: Weimer et al.: “automatically finding patches using genetic programming”, ICSE, 2009.

Test case

gcc(0,55)



GCD Example

Program passes test case

We need more test cases


Test case

gcc(0,55)

Test case

gcc(0,55)

gcc(1071,1029)



Test Cases and Fitness Function

Negative Test Cases Characterize the fault

Positive Test Cases Encode the functionality requirements

Fitness Function

The more passing test cases - the better the score

All test cases pass – repair found



GCD Example – Primary Repair


Test case

gcc(0,55)

Test case

gcc(0,55)

gcc(1071,1029)



The Zune Bug


Test cases



The Zune Bug – Possible Mutations



The Zune Bug – Solution



ASTOR

Automatic Software Transformation fOr program Repair

Tool for automatically repairing Java programs

Under GPL v2 (GNU General Public License)

Uses Spoon (library for Java code analysis and

manipulation)

Source: Martinez and Monperrrus: “ASTOR - Evolutionary Automatic Software Repair for Java”,

Technical Report hal-01075976, Inria, 2014



Outline



Repair



o Spreadsheets

Refactoring

Exam



GP for Spreadsheets – Mutations

Constants

Change Boolean values

Permutate digits

Increase / decrease number by 1

Use a random number

Change sign

References

Increase/decrease the borders of areas

Change a single reference

Formulas

Replace a binary operator with another binary operator

A1+A2 A1-A2

Replace a formula with another formula which can process the same arguments

SUM(A1:A4) AVG(A1:A4)

Remove parts of a formula

A3+A4*3 A3*3

Relocate parts of a formula

if(A1>1;A2;A3) if(A1>1;A3;A2)



Genetic Programming for Spreadsheet Repair I



Genetic Programming for Spreadsheet Repair II



Genetic Programming for Spreadsheets



Outline



Repair


Refactoring

Exam



Process of changing the internal structure of

a program without changing the functionality

Refactoring



How does refactoring

contribute to the quality

of spreadsheets?



BumbleBee

f1 ↔ f2

SUM(R)/COUNT(R) ↔ AVERAGE(R)

Parameterized references via variables

A1+A2+A3 ↔ SUM(A1:A3)

{i,j} + {i,j+1} ↔ SUM({i,j}:{j,j+1})

Areas

{i,j}+…+{m,n} ↔ SUM({i,j}:{m,n})

Source: Hermans and Dig: “BumbleBee: A Refactoring Environment for Spreadsheet Formulas”, FSE 2014.



TableProg

Source: Harris and Gulwani: “Spreadsheet Table Transformations from Examples”, PLDI, 2011.



TableProg




Outline



Repair



o Spreadsheets

Refactoring

Exam



Exam

General

List Fault Types

List Quality Assurance Techniques (+ subcategories)

Explain R1C1 cell reference system

Static Code Analysis techniques

Explain the terms Code Smells and Refactoring

List, explain and identity Software/Spreadsheet Code Smells

List and explain Static Spreadsheet Analysis Techniques (UCheck, …)

Spectrum-based fault localization

Explain and apply SFL to software snippets and spreadsheets

Explain the terms

o Observation matrix

o Error vector

o Similarity coefficient

o Best/worst/average case ranking

o Cone



Exam

Model-based fault localization

List + explain all parts of diagnosis problem

Explain the terms

o Conflict / Conflict set

o Diagnosis / Minimal diagnosis

o Hitting Set / Minimal hitting set

o SSA form

Solve simple examples via conflicts and hitting sets (hardware, simple software)

Write (in pseudo code) a dependency-/value-based model for a given spreadsheet

Explain how to compute double fault diagnoses

List, explain and compare (+/-) the different types of behavior models

Explain how to derive a dependency-based model from a value-based model (+ apply

by means of an example)

Explain coincidental correctness + list examples

Explain how MBSD for Software works

Compare SFL with MBSD w.r.t. complexity, granularity, input, result …



Exam

Automatic repair

Explain the terms

o Genetic Programming

o Mutation (+ list different types)

o Crossover (+ list / explain different types)

o Fitness function

Explain how automatic repair with genetic programming works for

software/spreadsheets



Haven’t you had enough

of spreadsheets yet?

Master Project

Diploma Thesis



Thank you for participating in this lecture.Are there any suggestions/wishes for changes/improvements?

Selected Topics of Software Technology 3 Repair & … Topics of Software Technology 3 2 Refactoring...

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