设计实时软件候选人scuola superiore anna pisa-atucb.pptx

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设计实时软件候选人scuola superiore anna pisa-atucb.pptx

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Ph.D.candidateScuolaSuperioreS.AnnaPisa-ItalyDesigningReal-TimeSoftwarevisitingprof.BaruahUniv.ofNorthCarolinaChapelHill-NC

Designingisoptimizingwhere:theapplicationisrepresentedbyatupleofdesignvariablesx;xisinadesignspaceF;therewardfunctionfexpressourgoal.Thedesignerhastofindtheapplicationx,suchthat:

ApplicationmodelApplicationmodel:tasksset{t1,t2,…,tn}.ti=(Ci,Ti,Di),where:Ciisthemaxcomputationtimeofti(WCET).Tiisthemininterarrivaltime(orperiod).Diistherelativedeadline.Ui=Ci/Tiistheutilizationfactorofti.Di￡Ti.Tasktx=(2,4,3)absolutedeadlinesactivationinstants

Designvariables/RewardfunctionThedesignerofRTsoftwarecanselectamong:manyimplementationsofanalgorithm(Ci);differentperiodsontheprogrammabletimers(Ti);differenttaskdeadlines(Di).Therewardfunctionf(x)typically:pushesagainsttheschedulability;increasesfor:biggerCi(betteralgorithm),smallerTi(thetaskisrunmoreoften),smallerDi(greaterresponsiveness).

ThedesignspaceFTheremaybesomeexternalconstraint:taskactivationperiodsdependonexternalevents;onlyabunchofimplementationisavailable.Theselectedtaskssetneedstobeschedulable!Weneedtodefineaschedulabilitycondition/constraint

UnalineaUnalineaAttempt1:ResponseTimeAniterativealgorithmappliedtothetaskset/applicationxxYESNOItdoesnotprovideinformativeresult:distancetotheboundary.

UsingResponseTimeforoptimizingNOdesignVar2designVar1rewardfunctionInitialsolution???????????Where?A“YES/NO”testisnotwellsuitedforoptimizationalgorithms!!

Attempt2:SimplerFormulationTheRTliteratureoffersmanysimpleronlysufficienttest:LiuLaylandtestHyperbolicBoundMorerestrictiveOnlyasuboptimumisfoundOpt.methodsmaybeappliedClosedFormulation

Attempt3*:Closedformulation+iff*thegoodoneaclosed(OKforoptimization)necessaryandsufficient(nosuboptimum