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SPEC Workshop 2008
Laboratory for Computer Architecture 1/27/2008
On the Object Orientedness of C++ programs in SPEC CPU 2006
Ciji Isen & Lizy K. JohnUniversity of Texas - Austin
1/27/2008
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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
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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
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C++ programs in SPEC cpu06
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Methodology
Performance counters
– Woodcrest(Intel), Power5+(IBM)
Benchmarks
– SPEC CPU 2006
– SPEC jbb2000
– SPECjvm98
Principle Component Analysis for Visualization
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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)
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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
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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
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NOC (Number of Children)
Definition: Number of immediate subclasses
Intuition: more children implies
– Greater reuse
– more influence on the design
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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
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RFC (Response for a Class)
Intuition: more methods executed per message implies
– More complexity for the class
– Complexity in testing and debugging
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Object Orientedness of C++ benchmarks in cpu06
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Object Orientedness of C++ benchmarks in cpu06
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Object Orientedness of C++ vs. java benchmarks
[DaCapo paper]
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Object Orientedness of C++ vs. java benchmarks
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Control flow Characteristics
Has OO nature affected control flow?
– branch compositions
– Branch misprediction
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Branch types - INT
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Branch types - FP
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Branch types - INT
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Branch types - FP
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Branch misprediction - INT
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Branch misprediction - FP
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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
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Questions
24 Laboratory for Computer Architecture 8/28/2007
