1. SPEC Workshop 2008 Laboratory for Computer Architecture1/27/2008 On the Object Orientedness of C++ programs in SPEC CPU 2006 Ciji Isen & Lizy K. John University of Texas - Austin 1/27/2008

2. SPEC Workshop 2008 2Laboratory for Computer Architecture1/27/2008 Introduction Object Oriented programming encourages –Code modularity, ease of design & maintenance –Inheritance & hierarchies –polymorphism –Dynamic Dispatch Should imply –Multiple function invocation –More functions –More indirect branching Increased control flow –particularly function calls and indirect branches

3. SPEC Workshop 2008 3Laboratory for Computer Architecture1/27/2008 Objective Object oriented nature of SPEC CPU2006 C++ programs –Measure using quantifiable metrics –Compare with other OO(SPEC java) benchmarks Has OO nature affected control flow? –branch compositions –Branch misprediction

4. SPEC Workshop 2008 4Laboratory for Computer Architecture1/27/2008 C++ programs in SPEC cpu06

5. SPEC Workshop 2008 5Laboratory for Computer Architecture1/27/2008 Methodology Performance counters –Woodcrest(Intel), Power5+(IBM) Benchmarks –SPEC CPU 2006 –SPEC jbb2000 –SPECjvm98 Principle Component Analysis for Visualization

6. SPEC Workshop 2008 6Laboratory for Computer Architecture1/27/2008 Object Oriented metrics CK (Chidamber and Kemerrer) metrics –WMC (Weighted Methods per Class) –DIT (Depth of Inheritance Tree) –NOC (Number of Children) –CBO (Coupling Between Objects) –RFC (Response for a Class)

7. SPEC Workshop 2008 7Laboratory for Computer Architecture1/27/2008 WMC (Weighted Methods per Class) if complexity is unity WMC = n Intuition: More methods implies –more time & effort to develop and maintain class –More methods inherited by children => more impact on children –Likely to be more application specific => less reuse

8. SPEC Workshop 2008 8Laboratory for Computer Architecture1/27/2008 DIT (Depth of Inheritance Tree) A measure of impact of ancestor classes Intuition: deeper class hierarchy implies –More methods inherited => more complexity –Greater design complexity –Greater potential to reuse inherited methods

9. SPEC Workshop 2008 9Laboratory for Computer Architecture1/27/2008 NOC (Number of Children) Definition: Number of immediate subclasses Intuition: more children implies –Greater reuse –more influence on the design

10. SPEC Workshop 2008 10Laboratory for Computer Architecture1/27/2008 CBO (Coupling Between Objects) Definition: The number of other classes to which a class is coupled –Via methods –Instance variables Intuition: more coupling implies –Bad for modularity. Less independence for class => difficult to reuse –Less independence => sensitive to change in other parts –More interaction => complexity in testing correctness

11. SPEC Workshop 2008 11Laboratory for Computer Architecture1/27/2008 RFC (Response for a Class) Intuition: more methods executed per message implies –More complexity for the class –Complexity in testing and debugging

12. SPEC Workshop 2008 12Laboratory for Computer Architecture1/27/2008 Object Orientedness of C++ benchmarks in cpu06

13. SPEC Workshop 2008 13Laboratory for Computer Architecture1/27/2008 Object Orientedness of C++ benchmarks in cpu06

14. SPEC Workshop 2008 14Laboratory for Computer Architecture1/27/2008 Object Orientedness of C++ vs. java benchmarks [ DaCapo paper ]

15. SPEC Workshop 2008 15Laboratory for Computer Architecture1/27/2008 Object Orientedness of C++ vs. java benchmarks

16. SPEC Workshop 2008 16Laboratory for Computer Architecture1/27/2008 Control flow Characteristics Has OO nature affected control flow? –branch compositions –Branch misprediction

17. SPEC Workshop 2008 17Laboratory for Computer Architecture1/27/2008 Branch types - INT

18. SPEC Workshop 2008 18Laboratory for Computer Architecture1/27/2008 Branch types - FP

19. SPEC Workshop 2008 19Laboratory for Computer Architecture1/27/2008 Branch types - INT

20. SPEC Workshop 2008 20Laboratory for Computer Architecture1/27/2008 Branch types - FP

21. SPEC Workshop 2008 21Laboratory for Computer Architecture1/27/2008 Branch misprediction - INT

22. SPEC Workshop 2008 22Laboratory for Computer Architecture1/27/2008 Branch misprediction - FP

23. SPEC Workshop 2008 23Laboratory for Computer Architecture1/27/2008 Summary Increased presence of C++ in SPEC CPU encouraging Measured object orientedness of C++ programs –Xalanckbmk,dealII & omnetpp – strong OO –OO nature of C++ programs not any worse than SPEC Java benchmarks Analyzed impact of OO nature on control flow –Control flow increase pronounced for FP –Xalanckbmk, dealII & omnetpp – higher % of function calls and indirect branches

24. SPEC Workshop 2008 24Laboratory for Computer Architecture1/27/2008 Questions 24Laboratory for Computer Architecture8/28/2007