簡介:EVOLUTIONARYSCHEDULINGOFPARALLELTASKSGRAPHSONTOHOMOGENEOUSCLUSTERSSASCHAHUNOLDLIGLABORATORYGRENOBLE,FRANCESASCHAHUNOLDIMAGFRJOACHIMLEPPINGROBOTICSRESEARCHINSTITUTETUDORTMUNDUNIVERSITY,GERMANYJOACHIMLEPPINGUDOEDUABSTRACTPARALLELTASKGRAPHSPTGSARISEWHENPARALLELPROGRAMSARECOMBINEDTOLARGERAPPLICATIONS,EG,SCIENTIFICWORKFLOWSSCHEDULINGTHESEPTGSONTOCLUSTERSISACHALLENGINGPROBLEMDUETOTHEADDITIONALDEGREEOFPARALLELISMSTEMMINGFROMMOLDABLETASKSMOSTALGORITHMSAREBASEDONTHEASSUMPTIONTHATTHEEXECUTIONTIMEOFAPARALLELTASKISMONOTONICALLYDECREASINGASTHENUMBEROFPROCESSORSINCREASESBUTTHISASSUMPTIONDOESNOTHOLDINPRACTICESINCEPARALLELPROGRAMSOFTENPERFORMBETTERIFTHENUMBEROFPROCESSORSISAMULTIPLEOFINTERNALLYUSEDBLOCKSIZESINTHISARTICLE,WEINTRODUCETHEEVOLUTIONARYMOLDABLETASKSCHEDULINGEMTSALGORITHMFORSCHEDULINGSTATICPTGSONTOHOMOGENEOUSCLUSTERSWEAPPLYANEVOLUTIONARYAPPROACHTODETERMINETHEPROCESSORALLOCATIONOFEACHTASKTHEEVOLUTIONARYSTRATEGYENSURESTHATEMTSCANBEUSEDWITHANYUNDERLYINGMODELFORPREDICTINGTHEEXECUTIONTIMEOFMOLDABLETASKSWITHTHEPURPOSEOFFINDINGSOLUTIONSQUICKLY,EMTSCONSIDERSRESULTSOFOTHERHEURISTICSEG,HCPA,MCPAASSTARTINGSOLUTIONSTHEEXPERIMENTALRESULTSSHOWTHATEMTSSIGNIFICANTLYREDUCESTHEMAKESPANOFPTGSCOMPAREDTOOTHERHEURISTICSFORBOTHNONMONOTONICALLYANDMONOTONICALLYDECREASINGMODELSKEYWORDSTASKSCHEDULINGPARALLELTASKSTASKGRAPHSEVOLUTIONARYALGORITHMCLUSTERIINTRODUCTIONSCIENTIFICWORKFLOWSAREANIMPORTANTTYPEOFPARALLELTASKGRAPHSANDAREOFTENPROCESSEDONCOMPUTATIONALGRIDSMANYSCIENTIFICWORKFLOWSCONTAINONLYAFEWPARALLELTASKSYET,ASCIRNEETALSTATED,ALMOST98OFPARALLELJOBSSUBMITTEDTOCOMPUTATIONALCLUSTERSAREMOLDABLE1THENUMBEROFPROCESSORSOFAMOLDABLETASKISDETERMINEDBEFOREITSEXECUTIONANDSTAYSUNCHANGEDDURINGEXECUTION2IFTHESEPARALLELTASKSARECOMBINED,APARALLELTASKGRAPHPTGARISESSEVERALALGORITHMSCANBEEXPRESSEDASPTGSSUCHASSTRASSEN’SMATRIXMULTIPLICATIONORTHEFASTFOURIERTRANSFORMATIONFFT3THENODESOFAPTGDENOTETHECOMPUTATIONSANDTHEEDGESDENOTEDATAORCONTROLDEPENDENCIESEXECUTINGAPTGLEADSTOAMIXEDPARALLELSCHEDULEASNODESAREIMPLEMENTEDINADATAPARALLELWAYANDINDEPENDENTTASKSCANBEEXECUTEDCONCURRENTLYLETUSEXAMINETHEEXECUTIONTIMEOFTHEPARALLELMATRIXMULTIPLICATIONROUTINEPDGEMMFROMSCALAPACK4FORTWOMATRIXSIZES,WHICHISSHOWNINFIGURE1ASWECANSEE,THEEXECUTIONTIMEISNOTMONOTONICALLYDECREASING,BUTMOSTSCHEDULINGALGORITHMSASSUMEAMONOTONICALLYDECREASINGMODELOFTHEEXECUTIONTIMEFORCOMPUTINGTHESCHEDULEHENCE,APPLYINGANONMONOTONICALLYDECREASINGMODELCANLEADTOINEFFICIENTDECISIONSOFTHESEALGORITHMSFORTHATREASON,WEFOCUSONTHEQUESTIONWHETHERANEVOLUTIONARYALGORITHMEAFORSCHEDULINGPTGSCANCOPEWITHIRREGULARITIESINTHEEXECUTIONTIMEMODELFORPARALLELTASKSWEINTRODUCETHEALGORITHMEMTS,WHICHCANBEUSEDWITHANARBITRARYEXECUTIONTIMEMODELWESHOWTHATEMTS,WHENCOMPAREDTOOTHERHEURISTICS,PRODUCESBETTERSCHEDULESWITHRESPECTTOTHEMAKESPANOBJECTIVETHISHOLDSFORNONMONOTONICALLYANDMONOTONICALLYDECREASINGEXECUTIONTIMEMODELSTHEPAPERISORGANIZEDASFOLLOWSSECTIONIIDETAILSTHEPROBLEMANDDISCUSSESRELATEDAPPROACHESINSECTIONIIITHEEVOLUTIONARYMETHODEMTSISPRESENTEDTHEMETHODOLOGYANDTHESETUPOFTHEEXPERIMENTSISDESCRIBEDINSECTIONIVTHEEXPERIMENTALRESULTSAREDISCUSSEDINSECTIONVANDSECTIONVIDRAWSCONCLUSIONSIIPROBLEMDESCRIPTIONANDRELATEDWORKAAPPLICATIONANDPLATFORMMODELAPTGMIXEDPARALLELAPPLICATIONCANBEREPRESENTEDBYADIRECTEDACYCLICGRAPHDAGGV,E,WHEREV{VI|I1,,V}ISASETOFNODESTHATREPRESENTTHETASKSANDE{EI,J|I,J∈{1,,V}{1,,V}}ISASETOFEDGESREPRESENTINGTASKINTERDEPENDENCIESAPTGCANBEEXECUTEDONPIDENTICALPROCESSORSINTERCONNECTEDBYANETWORK,SOTHATEACHPAIROFPROCESSORSCANCOMMUNICATEITISASSUMEDTHATTHEPARALLELTASKSAREMOLDABLE,IE,EXECUTABLEBYANARBITRARYNUMBEROFPROCESSORS1≤P≤P002005010020NUMBEROFPROCESSORSTIMES1024281632015020025NUMBEROFPROCESSORS2048162432FIGURE1PDGEMMTIMINGSONTHECRAYXT4OFLBNL2011IEEEINTERNATIONALCONFERENCEONCLUSTERCOMPUTING9780769545165/112600?2011IEEEDOI101109/CLUSTER201145344PROBLEMOFBEINGTRAPPEDINLOCALOPTIMA,BUTWHICHCANNOTBEGUARANTEEDTHEMAINADVANTAGESOFEVOLUTIONARYSEARCHSTRATEGIESARE1THEYCANCOPEWITHLARGEPROBLEMINSTANCES2THEYCANBEAPPLIEDTOANUNKNOWNSEARCHSPACEWITHOUTHAVINGAPRECISEMATHEMATICALMODELOFITSSTRUCTURE3THEYARECAPABLEOFOPTIMIZINGASOLUTIONSTARTINGANYWHEREINSEARCHSPACETHEDOWNSIDEISTHATEVOLUTIONARYAPPROACHESTENDTOCONVERGESLOWLYTOTHEOPTIMUM,ANDONEHASUSUALLYNOMEASUREOFHOWCLOSETHECURRENTRESULTISTOTHEOPTIMALSOLUTIONWHILEBEINGAWAREOFTHESEPROPERTIES,WEWANTTODESIGNANEVOLUTIONARYALGORITHMFORTHISSCHEDULINGPROBLEMTHATPROVIDESAGOODTRADEOFFBETWEENTHETIMEUSEDTOCOMPUTETHESOLUTIONANDTHERESULTINGMAKESPANSINCEWECANUSUALLYTRADETIMEFORSOLUTIONQUALITY,WEFOCUSONAGIVENTIMECONSTRAINTIIIALGORITHMEMTSTHEALGORITHMPRESENTEDINTHISSECTIONISBASEDONTHEAPPLICATIONANDPLATFORMMODELSPTG,WHICHWEREINTRODUCEDINSECTIONIIAINTHECONTEXTOFTHISARTICLE,AHOMOGENEOUSCLUSTERCOMPRISESTHESAMETYPEOFCOMPUTATIONALNODES,IE,THESAMEPROCESSORANDTHESAMEAMOUNTOFMEMORYINADDITION,COMMUNICATIONCOSTSBETWEENTASKSARENOTCONSIDEREDIFCOMMUNICATIONORDATAREDISTRIBUTIONSARENECESSARY,THEYNEEDTOBEINCLUDEDINTHEEXECUTIONTIMEMODELOFTHEPARALLELTASKSADESIGNINGTHEALGORITHMTHEEVOLUTIONARYMOLDABLETASKSCHEDULINGEMTSUTILIZESATWOSTEPAPPROACHFORSOLVINGTHESCHEDULINGPROBLEMINTHEFIRSTSTEP,THEALLOCATIONSOFEACHTASKARECOMPUTEDWHILEINTHESECONDSTEP,THEALLOCATIONSAREMAPPEDONTOTHEPROCESSORSOFTHESYSTEMMAPPINGFUNCTIONASTHEEXECUTIONTIMEMODELOFPARALLELTASKSHASNOINFLUENCEONTHEMAPPINGSTEP,WESTARTWITHDEFININGTHEMAPPINGFUNCTIONOFEMTSSINCETHEMAPPINGFUNCTIONALSOEVALUATESTHEFITNESSOFALLINDIVIDUALS,ITSHOULDBEASFASTASPOSSIBLEANDPRODUCESHORTSCHEDULESPREVIOUSWORKSHOWEDTHATALISTSCHEDULINGAPPROACHLEADSTOEFFICIENTSCHEDULES9INTHELISTSCHEDULINGALGORITHMUSEDBYEMTS,THEREADYNODESARESORTEDBYDECREASINGBOTTOMLEVELANDEACHREADYNODEVISMAPPEDTOTHEFIRSTPROCESSORSETTHATCONTAINSSVAVAILABLEPROCESSORS1THEFITNESSLEVELOFASETOFALLOCATIONSISDEFINEDASTHERESULTINGMAKESPANOFTHEPTGASMALLERMAKESPANCORRESPONDSTOABETTERFITNESSOFANEA’SINDIVIDUALALLOCATIONFUNCTIONTHEEAMODIFIESTHEPROCESSORALLOCATIONSOFTASKSANDITSGOALISTOFINDTHERIGHTALLOCATIONFOREACHTASKSOTHATTHERESULTINGFITNESSISOPTIMIZEDTHESETOFALLOCATIONSISENCODEDASINDIVIDUALIFORATASK1SVISTHEALLOCATIONSIZEOFNODEV,ANDTHEBOTTOMLEVELBLVISTHELENGTHOFTHELONGESTPATHFROMANODEVTOTHESINKOFTHEPTGINCLUDINGITSOWNEXECUTIONTIMEFIGURE2ENCODINGOFINDIVIDUALSTHEALLOCATIONSVIOFNODEVIISSTOREDATPOSITIONIVIOFPTGGJTHEINDIVIDUALIJIHOLDSTHENUMBEROFPROCESSORSALLOCATEDTOVIATPOSITIONITHUS,IJISVIFOR1≤I≤V,WHERESVIDENOTESTHECURRENTALLOCATIONOFTASKVIFIGURE2ILLUSTRATESTHISENCODINGOFTHEALLOCATIONSOFAPTGTHEDEPICTEDPTGCONTAINSFIVENODESANDEACHNODEPOSSESSESAPROCESSORALLOCATION,EG,THREEPROCESSORSAREALLOCATEDTONODE1ANINDIVIDUALISTHECOLLECTIONOFALLALLOCATIONSOFAPTGSO,THENUMBEROFPROCESSORSOFNODE1ISSTOREDATTHEFIRSTPOSITIONOFTHEINDIVIDUALTHEEAMODIFIESTHEINDIVIDUALSRANDOMLYTOOPTIMIZETHESCHEDULETHUS,THEOBJECTIVEFUNCTIONCANBEDEFINEDASFOLLOWSFORAGIVENPTGGANDFITNESSFUNCTIONFS→R,THEEATRIESTOFINDASETOFALLOCATIONSS{SV0,,SVV}THATMINIMIZESFIFWECONSIDERPTGSOFABOUT100TASKSANDAPLATFORMWITHHUNDREDSOFPROCESSORS,THESEARCHSPACETOFINDTHEBESTSOLUTIONS?ISENORMOUSNONETHELESS,EMTSMAYFINDANSWHICHISCLOSERTOS?THANTHESOLUTIONSPRODUCEDBYOTHERHEURISTICSTHISLEADSTOTWOMAINQUESTIONS1WHERESHOULDTHEEASTARTSEARCHINGORTOPUTITINANOTHERWAY,HOWSHOULDTHEORIGINALINDIVIDUALSBEINITIALIZED2HOWTOPRODUCENEWINDIVIDUALSFROMEXISTINGONESBRETRIEVINGSTARTINGSOLUTIONSTOOBTAINSTARTINGSOLUTIONS,EMTSMAKESUSEOFRESULTSPRODUCEDBYOTHERHEURISTICSINTHEPRESENTWORK,WEEXECUTETHEALLOCATIONFUNCTIONSOFMCPA11ANDHCPA10ANDENCODETHEIRRESULTSASINDIVIDUALSINTHEINITIALPOPULATIONTHESEALLOCATIONFUNCTIONSWERECHOSENBECAUSETHEYPRODUCESUFFICIENTLYGOODSOLUTIONSINASHORTAMOUNTOFTIMEADDITIONALLY,WEDESIGNEDANOTHERHEURISTICTOCREATEASTARTINGINDIVIDUALFIRST,THEBOTTOMLEVELOFEACHTASKISCOMPUTEDASSUMINGTHATEACHTASKISALLOCATEDTOONEPROCESSORHAVINGTHEBOTTOMLEVEL,EMTSDETERMINESTHECRITICALPATHOFTHEPTGTHEIDEAISTOASSIGNALLPROCESSORSOFTHESYSTEMTONODESONTHECRITICALPATHSINCESEVERALNODESONAPRECEDENCELEVELHAVESIMILAROREQUALCRITICALITYBOTTOMLEVEL,WECONSIDERSEVERALALMOSTCRITICALPATHSTOMAKETHISHEURISTICEFFECTIVEHENCE,WESEPARATETHENODESBYPRECEDENCELEVELDEPTHOFTHENODESFROMTHE346
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