Icpc08b.ppt
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The document discusses the challenges in understanding and maintaining software code, emphasizing that over 50% of maintenance time is spent on comprehending the program's features and requirements. It introduces automated tools and techniques for concern location, such as 'Cerberus,' which integrates information retrieval, execution tracing, and prune dependency analysis to identify and manage code concerns more effectively. Future work includes improving precision, accuracy, and generalization of the proposed methods.
![Prune dependency rule [ACOM’07]
□ Code is prune dependent on concern if
□ Pruning the concern requires removing or
altering the code
□ Must alter code that depends on removed
code
□ Prevent compile errors
□ Eliminate “dead code”
□ Easy to determine/approximate
11ICPC 2008Marc Eaddy](https://image.slidesharecdn.com/icpc08b-171206034151/85/Icpc08b-ppt-11-320.jpg)
![Vector space model [Salton]
□ Parse code and reqs doc to extract term vectors
□ NativeArray.js_join() method “native,” “array,” “join”
□ “Array.join” requirement “array,” “join”
□ Our contributions
□ Expand abbreviations
□ numconns number, connections, numberconnections
□ Index fields
□ Weigh terms (tf · idf)
□ Term frequency (tf)
□ Inverse document frequency (idf)
□ Similarity = cosine distance between document and
query vectors
14ICPC 2008Marc Eaddy](https://image.slidesharecdn.com/icpc08b-171206034151/85/Icpc08b-ppt-14-320.jpg)
Icpc08b.ppt
- 2. Motivation □ >50% of maintenance time spent trying to understand the program 2ICPC 2008Marc Eaddy
- 3. Motivation □ >50% of maintenance time spent trying to understand the program □ Where are the features, reqs, etc. in the code? 3ICPC 2008Marc Eaddy
- 4. Motivation □ >50% of maintenance time spent trying to understand the program □ Where are the features, reqs, etc. in the code? □ What is this code for? 4ICPC 2008Marc Eaddy
- 5. Motivation □ >50% of maintenance time spent trying to understand the program □ Where are the features, reqs, etc. in the code? □ What is this code for? □ Why is it hard to understand and change the program? 5ICPC 2008Marc Eaddy
- 6. What is a “concern?” □ Feature, requirement, design pattern, coding idiom, etc. □ Raison d'être for code □ Every line of code exists to satisfy some concern 6 Anything that affects the implementation of a program ICPC 2008Marc Eaddy
- 7. Concern location problem 7 Concerns Program Elements Concern–code relationship hard to obtain ICPC 2008Marc Eaddy
- 8. Concern location problem 8 Concerns Program Elements □ Concern–code relationship undocumented Concern–code relationship hard to obtain ICPC 2008Marc Eaddy
- 9. Concern location problem 9 Concerns Program Elements □ Concern–code relationship undocumented □ Reverse engineer the relationship □ (but, which one?) Concern–code relationship hard to obtain ICPC 2008Marc Eaddy
- 10. Software pruning □ Remove code that supports certain features, reqs, etc. □ Reduce program’s footprint □ Support different platforms □ Simplify program 10ICPC 2008Marc Eaddy
- 11. Prune dependency rule [ACOM’07] □ Code is prune dependent on concern if □ Pruning the concern requires removing or altering the code □ Must alter code that depends on removed code □ Prevent compile errors □ Eliminate “dead code” □ Easy to determine/approximate 11ICPC 2008Marc Eaddy
- 12. Automated concern location □ Experts mine clues in code, docs, etc. □ Existing techniques use 1 or 2 experts only □ Our solution: Cerberus 1. Information retrieval 2. Execution tracing 3. Prune dependency analysis 12 Concern–code relationship predicted by an “expert” ICPC 2008Marc Eaddy
- 13. IR-based concern location □ i.e., Google for code □ Program entities are documents □ Requirements are queries 13 join Id_joi njs_join( ) Requirement “Array.join” Source Code ICPC 2008Marc Eaddy
- 14. Vector space model [Salton] □ Parse code and reqs doc to extract term vectors □ NativeArray.js_join() method “native,” “array,” “join” □ “Array.join” requirement “array,” “join” □ Our contributions □ Expand abbreviations □ numconns number, connections, numberconnections □ Index fields □ Weigh terms (tf · idf) □ Term frequency (tf) □ Inverse document frequency (idf) □ Similarity = cosine distance between document and query vectors 14ICPC 2008Marc Eaddy
- 15. Tracing-based concern location □ Observe elements activated when concern is exercised □ Unit tests for each concern □ e.g., find elements uniquely activated by a concern 15ICPC 2008Marc Eaddy
- 16. Tracing-based concern location □ Observe elements activated when concern is exercised □ Unit tests for each concern □ e.g., find elements uniquely activated by a concern 16 Call Graph js_joi n var a = new Array(1, 2); if (a.join(',') == "1,2") { print "Test passed"; } else { print "Test failed"; js_construct Unit Test for “Array.join” Marc Eaddy
- 17. Tracing-based concern location □ Observe elements activated when concern is exercised □ Unit tests for each concern □ e.g., find elements uniquely activated by a concern 17 Call Graph js_joi n var a = new Array(1, 2); if (a.join(',') == "1,2") { print "Test passed"; } else { print "Test failed"; js_construct Unit Test for “Array.join” Marc Eaddy
- 18. Prune dependency analysis □ Infer relevant elements based on structural relationship to relevant element e (seed) □ Assumes we already have some seeds □ Prune dependency analysis □ Determines prune dependency rule using program analysis □ Find references to e □ Find superclasses and subclasses of e 18ICPC 2008Marc Eaddy
- 19. PDA example 19 C AB foofoomain bar calls contains refs containscontains contains Program Dependency Graph interface A { public void foo(); } public class B implements A { public void foo() { ... } public void bar() { ... } } public class C { public static void main() { B b = new B(); b.bar(); } Source Code inherits ICPC 2008Marc Eaddy
- 20. 20 C AB foofoomain bar callscalls contains refs containscontains contains Program Dependency Graph interface A { public void foo(); } public class B implements A { public void foo() { ... } public void bar() { ... } } public class C { public static void main() { B b = new B(); b.bar(); } Source Code inherits PDA example ICPC 2008Marc Eaddy
- 21. PDA example 21 C AB foofoomain bar containscontains refs containscontainscontains contains Program Dependency Graph interface A { public void foo(); } public class B implements A { public void foo() { ... } public void bar() { ... } } public class C { public static void main() { B b = new B(); b.bar(); } Source Code calls inherits ICPC 2008Marc Eaddy
- 22. PDA example 22 Program Dependency Graph interface A { public void foo(); } public class B implements A { public void foo() { ... } public void bar() { ... } } public class C { public static void main() { B b = new B(); b.bar(); } Source Code inheritsinherits C AB foofoomain bar refs contains contains calls contains contains ICPC 2008Marc Eaddy
- 23. PDA example 23 Program Dependency Graph interface A { public void foo(); } public class B implements A { public void foo() { ... } public void bar() { ... } } public class C { public static void main() { B b = new B(); b.bar(); } Source Code C AB foofoomain bar refs contains containscontains calls contains contains inherits ICPC 2008Marc Eaddy
- 25. Cerberus PROMESIR + SNIAFL 25ICPC 2008Marc Eaddy ≈
- 26. Cerberus effectiveness Marc Eaddy 26 Cerberus
- 27. Ignoring “No results found” 27 Cerberus Marc Eaddy
- 28. Future work □ Improve PDA □ Reimplemented using Soot and Polyglot □ Generalize using prune dependency predicates □ Improve precision using points-to analysis □ Improve accuracy using □Dominator heuristic □Variable liveness analysis □ Improve accuracy of Cerberus □ Combine experts using matrix linear regression 28ICPC 2008Marc Eaddy
- 29. Cerberus contributions □ Effectively combined 3 concern location techniques □ PDA boosts performance of other techniques Marc Eaddy ICPC 2008 29 Program Dependency Graph interface A { public void foo(); } public class B implements A { public void foo() { ... } public void bar() { ... } } public class C { public static void main() { B b = new B(); b.bar(); } Source Code C AB foofoomain bar refs contains contains calls contains contains
- 30. Questions? Marc Eaddy Columbia University eaddy@cs.columbia.edu 30ICPC 2008Marc Eaddy