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SummaryOfSeveralAutoencodermodels
Presentor:JiGao
DepartmentofComputerScience,UniversityofVirginiahttps://qdata.github.io/deep2Read/
List
• AdversarialAutoencoders• PixelGAN Autoencoders• GeneratinganddesigningDNAwithdeepgenerativemodels• FeedbackGAN(FBGAN)forDNA:aNovelFeedback-LoopArchitectureforOptimizingProteinFunctions• AutoregressiveGenerativeAdversarialNetworks
AdversarialautoencodersAlireza Makhzani, JonathonShlens,Navdeep Jaitly, IanGoodfellow,BrendanFrey
• Useadversariallearningintrainingautoencoders
Autoencoders
• Autoencoder
• Decoder=Generator:Startfromaprior(oftennormaldistribution),producesample
Autoencoders
WhyDecoderwork?• Anydistributionin𝑑 dimensioncanbegeneratedbyasufficientlycomplicatedfunctionon𝑑 normallydistributionalvariables.
Whynotdirectlyoptimizedecoder?
• Ifdirectlyoptimizedecoderviasampling,itwilltakeexponentiallynumberofsamples(Andalsoexponentiallyparameters)• Alotofthesamplingareuseless,foraX,weonlyneedthepartofzthatarelikelytoproduceX• FindmostlikelyztoproduceXcansavehugeamountoftimeandmaketheprocesstractable
VariationalAutoencoder
𝐷#$(𝑄(𝑧)||𝑃(𝑧|𝑥)) = 𝐸.~0[log𝑄 𝑧 − log𝑃(𝑧|𝑥)]
= 𝐸.~0[log𝑄 𝑧 − log𝑃 𝑥 𝑧 − log𝑃 𝑧 + log𝑃(𝑥)]
Latentvariable𝑧~𝑃(𝑧) Ifwesample𝑄(𝑧) toapproximate𝑃(𝑥),wehave
log𝑃(𝑥) − 𝐷#$(𝑄(𝑧)||𝑃(𝑧|𝑥)) = 𝐸.~0[log𝑃 𝑧|𝑥 ] − 𝐷#$(𝑄(𝑧)||𝑃(𝑧))
Bayesian
Reasonabletolet𝑄(𝑧) conditionedonx.
Wehave:log𝑃(𝑥) ≥ 𝐸.~0[log𝑃 𝑧|𝑥 ] − 𝐷#$(𝑄(𝑧|𝑥)||𝑃(𝑧))
Variationalbound
VariationalAutoencoderlog𝑃(𝑥) ≥ 𝐸.~0[log𝑃 𝑧|𝑥 ] − 𝐷#$(𝑄(𝑧|𝑥)||𝑃(𝑧))InVAE,welet𝑄 𝑧 𝑥 = 𝑁(𝑧|𝜇 𝑥;𝜃 , Σ(𝑥; 𝜃))
Inthiscase:
Samplexandz,wehave
Posterier
• GaussianPosterier
VariationalAutoencoder
FromTutorialonVariationalAutoencoders https://arxiv.org/abs/1606.05908
Adversarialautoencoder
• VAEworkson
• 𝐷#$(𝑄 𝑧 𝑥 ||𝑃 𝑧 ) termcanbeoptimizedinadversarialtraining• Trainrepeatedlyintwosteps:1.Maximize𝐸.~0[log𝑃 𝑥|𝑧 ]2.Minimizethedistancebetween𝑄(𝑧|𝑥) and𝑃(𝑧)
log𝑃(𝑥) ≥ 𝐸.~0[log𝑃 𝑥|𝑧 ] − 𝐷#$(𝑄(𝑧|𝑥)||𝑃(𝑧))
Freedomofchoosingq()
• ComparetoVAE,inthisformitcanbeoptimizedusingseveraldifferentways:• 1.Deterministic:𝑞 𝑧 𝑥 isadeterministicfunctiononx• 2.Gaussianposterior:𝑄 𝑧 𝑥 = 𝑁 𝑧 𝜇 𝑥; 𝜃 , Σ 𝑥; 𝜃 similartoVAE.Canusethesamereparameterization• 3.Universalapproximator posterior,𝑞 𝑧 𝑥, 𝜂 = 𝛿(𝑧 − 𝑓(𝑥, 𝜂))
Adversarialautoencoderperformance
Loglikelihood
Supervisedlearning
• Fullysupervisedlearningtogeneratesamplesinaparticularway
Semi-supervisedlearning
• 2adversarialnets:Onewithcategoricaldata• Traininthreephases:• 1.Reconstructionphase• 2.Regularizationphase• 3.Semi-supervisedphase
PixelGAN AutoencodersAlirezaMakhzani,BrendanFrey
PixelGAN Autoencoders
• UsePixelCNN asthegenerativepath• PixelCNN conditionedonq(z|x)
Categoricalprior
Experiment
GeneratinganddesigningDNAwithdeepgenerativemodelsNathanKilloran,LeoJ.Lee,AndrewDelong,DavidDuvenaud,BrendanJ.Frey
• 2017• ThreeapproachestogenerateDNAsequence:• 1.GAN• 2.Activationmaximization(DeepDream)• 3.Ajointof1and2
GANondiscreteoutput
• DNAsequenceisdiscrete,similartoNLPtask• WGAN-GPcangeneratethesequenceinthedirectway:
LetGANdirectlyoutputone-hotcharacterembeddings fromalatentvectorwithoutanydiscretesamplingstep.Softmax directlypassedtocritic.
GANonDNA
• UsesuchmethodonDNA:
ActivationMaximization
• ThemethodisactuallyDeepDream:• Startfromsamplex,makeittargetatacertainpropertyt(output)• 𝑥 → 𝑥 + 𝜖∇E𝑡• Worksoncontinuouscase,soneedtorelaxdiscretesymbolsintocontinuouscase
Jointmethod
• UseGANtogeneratesample• Useactivationmaximizationtooptimizeasampletocertainproperties
Experiment:Motif
• Samplesequencestunedtohaveahighpredictorscore
Experiment
FeedbackGAN(FBGAN)forDNA:aNovelFeedback-LoopArchitectureforOptimizingProteinFunctionsAnvita Gupta,JamesZou
• 2018• Target:DesignDNAautomaticallyfollowingsomeproperties
FeedbackGAN
• (a)WGAN-GPasgenerator• (b)Analyzer:supposetobeanyfunction• Ratethegeneratedsamples• Markthetopsortedsamplesasrealsamples
• (c)Feedbackscheme• Sendthetopsortedsamplebacktothediscriminator
Evaluation
• Beforetraining,3.125%ofsequencesinitially followedthecorrectgenestructure• Aftertraining,77.08%ofsampledsequencescontainedthecorrectgenestructure
AutoregressiveGenerativeAdversarialNetworksYasin Yazici,Kim-HuiYap,StefanWinkler
• ICLR18Workshop
ARGAN
• ReplacediscriminatorintoaCNN+Autoregressivemodel• Motivation:anautoregressivemodelwouldmodelthefeaturedistributionbetterthanfullyconnectedlayers
S-ARGANandC-ARGAN
Result