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Aspect-Oriented Extensions to HEP Frameworks

Aspect-Oriented Extensions to HEP Frameworks. Paolo Calafiura, Craig E. Tull presented by Wim Lavrjisen LBNL NERSC/HCG. What is AOP?. Aspect-Oriented Programming (AOP) Methodology to decompose problems into Functional components (e.g. OO classes)

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Aspect-Oriented Extensions to HEP Frameworks

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  1. Aspect-Oriented Extensions to HEP Frameworks Paolo Calafiura, Craig E. Tull presented by Wim Lavrjisen LBNL NERSC/HCG

  2. What is AOP? Aspect-Oriented Programming (AOP) • Methodology to decompose problems into • Functional components (e.g. OO classes) • Aspectsthatcrosscutfunctional components • Technology to weave these components and aspects into an implementation • Started at Xerox PARC in late 90s • About 10 actively supported tools available for AO software development. See http://www.aosd.net Aspect-Oriented Extensions to HEP Frameworks

  3. Display Figure FigureElement moveBy(int, int) makePoint(..)makeLine(..) • DisplayUpdating is an Aspect that crosscuts the class tree, capturing a commonality not readily expressible using inheritance Point Line getX()getY()setX(int)setY(int)moveBy(int, int) getP1()getP2()setP1(Point)setP2(Point)moveBy(int, int) DisplayUpdating The Figure Editor Example • FigureElement captures structural commonalities of Point and Line • Element Factory • Element Movement Aspect-Oriented Extensions to HEP Frameworks

  4. The AOP Promise StatusCode AthenaOutputStream::decodeAcceptAlgs( ) { StatusCode result = decodeAlgorithms( m_acceptNames, m_acceptAlgs ); MsgStream log(msgSvc(), name()); if (m_acceptNames.value().size()) { log << MSG::DEBUG << "Found AcceptNames: " ; vector<string>::const_iterator first = m_acceptNames.value().begin(); vector<string>::const_iterator last = m_acceptNames.value().end(); for (; first != last; ++first) { log << MSG::DEBUG << (*first); } log << MSG::DEBUG << endreq; } return result; } Localize implementation of aspects cutting across “natural” problem decomposition Logging, Thread synchr, Tracing,… StatusCode AthenaOutputStream::decodeVetoAlgs( ) { StatusCode result = decodeAlgorithms( m_vetoNames, m_vetoAlgs ); MsgStream log(msgSvc(), name()); if (m_vetoNames.value().size()) { log << MSG::DEBUG << "Found VetoNames: " ; vector<string>::const_iterator first = m_vetoNames.value().begin(); vector<string>::const_iterator last = m_vetoNames.value().end(); for (; first != last; ++first) { log << MSG::DEBUG << (*first); } log << MSG::DEBUG << endreq; } else { log << MSG::DEBUG << "No VetoNames found " << endreq; } return result; } Claim is that AOP will complement not replaceOOP, components, generic programming, etc. Logging Aspect Aspect-Oriented Extensions to HEP Frameworks

  5. AspectC++ An aspect-oriented extension to C++ modeled on the popular aspectJ language • ac++compiler: weaves aspect code into original sources, emits standard C++ • Supports library-based development • Open-source, release 0.9pre1 July 04 • Actively developed and supported http://www.aspectc.org Aspect-Oriented Extensions to HEP Frameworks

  6. Quick ac++ Syntax Overview http://www.aspectc.org/Documentation.5.0.html An aspect captures a crosscutting concern • Otherwise behaves very much like a C++ class aspect RedirectOstream: virtual public IProperty { private: ISvcLocator* m_locator; public: const MsgStream& log() const; }; Aspect-Oriented Extensions to HEP Frameworks

  7. Quick ac++ Syntax Overview - 2 An advice adds behaviour to an aspect: • what to do before, after, and around certain joinpoints in the control flow aspect RedirectOstream { advice call("ostream & ostream::operator <<(const char*&)")&& args(what): around(const char*& what) { log() << what; } }; //streamlined example, life more complicated Aspect-Oriented Extensions to HEP Frameworks

  8. Quick ac++ Syntax Overview - 3 An advice can (re-)use a pointcut(set of joinpoints) to specify when should run • A pointcut can be ’virtual’, allowing to abstract the “when” of an aspect. aspect DisplayUpdate { pointcut virtual moved() = call(“% FigureElement.moveBy(int, int)”) || call(“void Point.set%(double)”) || call(“void Line.set%(Point)”); }; Aspect-Oriented Extensions to HEP Frameworks

  9. Quick ac++ Syntax Overview - 4 Rich joinpoint API, including accessors to • active objects (this, that, arg, result,…) • reflective info (signatures, types,…) aspect ViewUpdate : public DisplayUpdating { advice moved() : after() { m_display.redraw( tjp->that()); } }; aspect TraceUpdate : public DisplayUpdating { advice moved() : before() { cout << thisJoinPoint->toString() << endl; } }; Aspect-Oriented Extensions to HEP Frameworks

  10. Quick ac++ Syntax Overview - 5 An aspect can introduce in C++ classes • methods, data members and even base classes pointcut mapkeys()=“String || UnsignedLong"; aspect threadSafe { private: advice mapkeys() : baseclass(ThreadNo); }; Aspect-Oriented Extensions to HEP Frameworks

  11. Application Manager Converter Converter Sequencer Converter Event LoopMgr Event Store Data Files Message Service Persistency Service H H H H H StoreGateSvc JobOptions Service Algorithm Algorithm T T T D D Particle Prop. Service Data Files D D StoreGateSvc D D Persistency Service D D D Detector Store Other Services Auditors Histogram Service Athena/Gaudi: our target architecture Aspect-Oriented Extensions to HEP Frameworks

  12. Examples of HEP Cross-cutting Concerns Logging • Redirect cout/cerr output to MsgStream • But templated joinpoints not yet supported by ac++ • Add reflection info to errors/exceptions Interactive Job Configuration • Invoke call back whenever a property attribute of an object is set/modified • Gaudi support this for attributes inheriting from a Property base class • Ideally use “set” pointcut function on attributes • “set” not yet supported by ac++ Aspect-Oriented Extensions to HEP Frameworks

  13. Examples of HEP Cross-cutting concerns Data Object History (aka Provenance) • Gaudi History keeps track of which Algorithm recorded data object to TDS • Aspect also allows to keep track of data object creator and of who modified it. • Pointcut defined as OR of all non-const methods of a data object class Reference Management • Check that objects recorded on TDS are not accidentally deleted. • Check that retrieved services/tools are released. Aspect-Oriented Extensions to HEP Frameworks

  14. Application Manager MotherThread Event LoopMgr Event LoopMgr Message Service StoreGateSvc StoreGateSvc JobOptions Service Algorithm Algorithm Algorithm Algorithm StoreGateSvc StoreGateSvc Thread 1 Thread 2 Thread-aware Naming Service All objects in Gaudi located by name (and type ID). Transparently extend naming scheme to handle MT copies Aspect-Oriented Extensions to HEP Frameworks

  15. Thread-aware Naming Service: C++ Solution When multiple copies exist attach thread ID to object name • Handled in Gaudi using helper classes, but • Hard to edit all name-server codes that needed to use the helpers • Shotgun Surgery (one of Fowler’s “code smells”) • Helper code clutters original (non MT) name-server codes Aspect-Oriented Extensions to HEP Frameworks

  16. Thread-aware Naming Service:AOP Solution • Extend the name type inserting the threadID helper as a base class advice mapkeys() : baseclass(ThreadNo); • Use the new type where the old one was • Still hard to define the pointcut • no more Shotgun surgery: everything in the aspect advice execution("% theLocator::registerService(...)") && args(k, pService) : before(const mapkey& k, IService* pService) {…} Aspect-Oriented Extensions to HEP Frameworks

  17. Do we need AOP? • Helps dealing with constantly evolving requirements  • “Thinking in aspects” provides a vocabulary, if not yet a paradigm, to identify and design cross-cutting concerns. • C++ offers native implementation techniques • Macros (yes, macros!) • Policy-based designs using templated wrappers • But aspects are more compact and powerful using AOP tools • Makes understanding control flow even harder Aspect-Oriented Extensions to HEP Frameworks

  18. Can we use AOP? Not yet (at least not for LHC experiments) • ac++ (our favourite) still not quite ready • Open-sourced, actively developed • Well specified (builds on aspectJ) • Insufficiently documented • Probably not ready for large-scale builds • Slow, no dependency management tool yet • Not yet std C++ compatible • No templates, limited standard library • Further investigate physical coupling. Aspect-Oriented Extensions to HEP Frameworks

  19. AAcknowledgements We would like to thank the ac++ team and community for their support and advice

  20. ac++ implementation • A preprocessor • Emits std c++ • No run-time overhead • Limitations (rel 0.9) • No dependency resolution • Error detection and reporting (~templates) • No namespaces • Limited STL support • No templates in aspects Aspect-Oriented Extensions to HEP Frameworks

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