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1、Chapter:EnsembleMLPClassifierDesignTerryWindeattCentreforVision,SpeechandSignalProc.,DepartmentofElectronicEngineering,UniversityofSurrey,Guildford,Surrey,UnitedKingdomGU27XHt.windeatt@surrey.ac.ukAbstract.Multi-layerperceptrons(MLP)makepowerfulclassifiersthatmayprovidesuperiorperformancecomparedw
2、ithotherclassifiers,butareoftencriticizedforthenumberoffreeparameters.Mostcommonly,parametersaresetwiththehelpofeitheravalidationsetorcross-validationtechniques,butthereisnoguaranteethatapseudo-testsetisrepresentative.FurtherdifficultieswithMLPsincludelongtrainingtimesandlocalminima.Inthischapter,
3、anensembleofMLPclassifiersisproposedtosolvetheseproblems.Parameterselectionforoptimalperformanceisperformedusingmeasuresthatcorrelatewellwithgeneralisationerror.1IntroductionThetopicofthischapterconcernssolvingproblemsinpatternrecognitionusingacombinationofneuralnetworkclassifiers.Patternclassific
4、ationinvolvesassignmentofanobjecttooneofseveralpre-specifiedcategoriesorclasses,andisakeycomponentinmanydatainterpretationactivities.Herewefocusonclassifiersthatlearnfromexamples,anditisassumedthateachexamplepatternisrepresentedbyasetofnumbers,whichareknownasthepatternfeatures.Inthecaseoffacerecog
5、nition(Section5),thesefeaturesconsistofnumbersrepresentingdifferentaspectsoffacialfeatures.Inordertodesignalearningsystemitiscustomarytodividetheexamplepatternsintotwosets,atrainingsettodesigntheclassifierandatestset,whichissubsequentlyusedtopredicttheperformancewhenpreviouslyunseenexamplesareappl
6、ied.Aproblemariseswhentherearemanyfeaturesandrelativelyfewtrainingexamples,andtheclassifiercanlearnthetrainingsettoowell,knownasover-fittingsothatperformanceonthetestsetdegrades.Automatingtheclassificationtasktoachieveoptimalperformancehasbeenstudiedinthetraditionalfieldsofpatternrecognition,machi
7、nelearningandneuralnetworksaswellasnewerdisciplinessuchasdatafusion,dataminingandknowledgediscovery.Traditionally,theapproachthathasbeenusedinthedesignofpatternclassificationsystemsistoexperimentallyassesstheperf