Toward Explainable Uncertainty · Toward Explainable Uncertainty Alan Fern and Tom Die/erich School...
Transcript of Toward Explainable Uncertainty · Toward Explainable Uncertainty Alan Fern and Tom Die/erich School...
Toward Explainable Uncertainty
AlanFernandTomDie/erich
SchoolofElectricalEngineeringandComputerScienceOregonStateUniversity
Goal 1: Uncertainty Aware ML Systems
• Designmachinelearningsystemsthat“knowwhattheyknow”[Li,Li/man,WalshICML’08]• ProvideguaranteesonpredicNons• Allowsystemstoabstainand/orproduceambiguouspredicNons
• Achievethisin:• ClosedWorlds=KnownUnknowns• OpenWorlds=UnknownUnknowns
• Why?• SafeandTrustworthyAI• EndUserAcceptability• ComputaNonalEfficiency–usemorecomplexmodelifsimplermodelisuncertain
Goal 2: Transparent Uncertainty in ML Systems
• Designmachinelearningsystemsthatcan“explaintheiruncertainty”• Giveinsightintowhytheyabstainedorproducedambiguousanswer
• Achievethesegoalsin:• ClosedWorlds=KnownUnknowns• OpenWorlds=UnknownUnknowns
• Why?• Basisforfeedbacktolearningsystems• BasisforinvesNgaNnganomalies• Mechanismforbuildingtrust
Outline
• ConformalPredicNonforUncertaintyAwareClassificaNon• Empiricalperformanceinclosedworlds• Empiricalperformanceinopenworlds• NoteffecNveinopenworlds→SuggestsintegraNngwithanomalydetecNon
• ExplanaNonsforAnomalyDetecNon• WhatisananomalyexplanaNon?• HowtocomputeexplanaNons?• HowtoevaluateexplanaNons?
Standard ClassificaCon
Predictor
Animal
Human
Human
Classes:{Human,Animal,Hybrid}
UncertaintyinthesystemisnotmadeexplicitinthepredicNons.
Conformal PredicCon [Vovk et al., 2005]
ConformalPredictor
{Animal,Hybrid}
{Human}
{Animal,Human,Hybrid}
Classes:{Human,Animal,Hybrid}
• Conformalpredictorsoutputsetsoflabels.
• Labelsetiscorrectifitcontainstruelabel.
MostbasictypeofexplanaNonofuncertainty
Conformal PredicCon: Accuracy
ConformalPredictor
{Animal,Hybrid}
{Human}
{Animal,Human,Hybrid}
Classes:{Human,Animal,Hybrid}
AccuracyConstraint(e.g.95%)
Requirement:mustreturnlabelsetsthatachieveaccuracyconstraint
Conformal PredicCon: Accuracy
ConformalPredictor
{Animal,Human,Hybrid}
{Animal,Human,Hybrid}
{Animal,Human,Hybrid}
Classes:{Human,Animal,Hybrid}
AccuracyConstraint(e.g.95%)
Butwecanget100%accuracybyalwaysreturningalllabels.
Requirement:mustreturnlabelsetsthatachieveaccuracyconstraint
Conformal PredicCon: Ambiguity
ConformalPredictor
{Animal,Hybrid}
{Human}
{Animal,Human,Hybrid}
Classes:{Human,Animal,Hybrid}
AccuracyConstraint(e.g.95%)
Ambiguity= # of predicted labels−1/# of labels−1 ∈[𝟎,𝟏]
Wanttominimizeambiguityofreturnedlabelsets.
ambiguity=0
ambiguity=1
ambiguity=1/2
Conformal PredicCon: Constrained ObjecCve
ConformalPredictor
Classes:{Human,Animal,Hybrid}
AccuracyConstraint(e.g.95%)
Minimize:expectedambiguitySubjectto:accuracyconstraint
{Animal,Hybrid}
{Human}
{Animal,Human,Hybrid}
Inside Conformal PredicCon
YourFavoritePredictor
ConformalPredicNon
Non-conformityScores[human,animal,hybrid]
AccuracyConstraint(e.g.95%)
ConformalpredicNonisawrapperaroundanypredictorthatproduces“non-conformityscores”overtheclassesrelaNvetotrainingdataPredictorqualityinfluencesambiguityofconformalpredicNon.
{Animal,Hybrid}
{Human}
{Animal,Human,Hybrid}
[6,0.5,0.1]
[0.1,0.5,0.15]
[0.01,10,7]
TrainingData
Non-conformity Scores: Nearest Neighbor
NearestNeighbor NonConformity(X,Y)= distance to closest Y/distance to closest non Y
X
TrainingData
X
𝑌∈{human,animal,hybrid}
Non-conformity Scores: Random Forest
RandomForest NonConformity(X,Y)= # of trees not predicting Y/# of trees
X
X
animal hybrid human hybrid human
NonConformity(X,animal)=4/5NonConformity(X,human)=3/5NonConformity(X,hybrid)=3/5
Conformal PredicCon: Neural Networks
NeuralNetworks NonConformity(X,Y)= max output for not Y /output for Y
X
X NonConformity(X,animal)=0.8/0.15=5.3NonConformity(X,human)=0.8/0.05=16NonConformity(X,hybrid)=0.15/0.8=0.19
0.8hybrids
0.15animal
0.05human
Inside Conformal PredicCon
YourFavoritePredictor
ConformalPredicNon
AccuracyConstraint(e.g.95%)TrainingData
CalibraNonData
Non-ConformityScoreHistogram
Non-conformityScores[0.05,0.9,0.1]
AnimalHybridHuman
Areatleast5%ofthecalibraNonscoresweirderthanthislabelwiththisexample?
Inside Conformal PredicCon Non-ConformityScoreHistogram
AnimalHybridHuman
Areatleast5%ofthecalibraNonscoresweirderthanthislabelwiththisexample?
YourFavoritePredictor
ConformalPredicNon
AccuracyConstraint(e.g.95%)TrainingData
CalibraNonData
Non-conformityScores[0.05,0.9,0.1]
Conformal PredicCon: Empirical EvaluaCon
• VeryfewempiricalevaluaNonsofconformalpredicNon• Rarelylookatambiguity
• MostresultsforNearestNeighbor--otenyieldslargeambiguityinourexperience
• Howdoesambiguityvarywithamountoftrainingdatainclosedworlds?
• HowdoesconformalpredicNonperforminopenworlds?
Closed World: Random Forest Results
• Arrhythmia:452datapoints,13labels,majorclassimbalances
• Cardiotocography:2126instances,10labels,balancedclasses
• ImageSegmentaNon:2310instances,8labels,balancedclasses
• Iris:150instances,3labels,balancedclasses
Closed World: Random Forest
Numberofexamples Numberofexamples
AccuracyConstraint=95%Accuracy
Arrhythmia
Ambiguity
Arrhythmia
OtherdatasetsarequalitaNvelysimilar.
Closed World: Random Forest
AccuracyConstraint
Ambiguity
Arrhythmia
AccuracyConstraint
Ambiguity
Cardiotocography
Closed World: Random Forest
AccuracyConstraint
Ambiguity
SegmentaNon
AccuracyConstraint
Ambiguity
Iris
Closed World: Random Forest
• Overall,wesee“idealbehavior”onthesedatasets.• Closeto0ambiguitywithsmallamountofdata.
Closed World: ConvoluConal Network: Cifar 10
Closed World: Deep Net
NumberofCalibraNonExamples
Ambiguity
Cifar10
AccuracyConstraint
Ambiguity
Cifar10
Closed World ObservaCons
• Overall,wesee“idealbehavior”onthesedatasetsforbothrandomforestandconvoluNonalnetwork.
• Closeto0ambiguitywithsmallamountofdata.
• Neuralnetworkveryrarelyabstains(negaNveambiguity)comparedtotherandomforest
Open World: Conformal PredicCon
Predictor
{Animal}
{Human,Animal}
???
TrainingLabels={Human,Animal,Hybrid}
ConformalPredicNon
Wedon’thavealabelfor“monster”!
Onlyreasonableoutputistoabstain(emptyset)
∅
Open World Experiments
• Feednovelclassestoconformalpredictor
• RandomForest:withheldalabelfromeachtrainingset
• Convolu@onalNetwork:feeditimagesthathavenothingtodowithCifar10
Open World: Random Forest
Numberofexamples
Ambiguity
Arrhythmia
NumberofexamplesAm
biguity
Cardiotocography
Abstains=Knowswhatitknows
Confidentinsinglelabel
Ambiguityforjustnovelclasses
Open World: Random Forest
Numberofexamples
Ambiguity
SegmentaNon
NumberofexamplesAm
biguity
Cardiotocography
Ambiguityforjustnovelclasses
Confidentinsinglelabel
Confidentinsinglelabel
Open World: ConvoluConal Network
Nethackspritesheetimages
Open World: ConvoluConal Network
LearningCurvesvsCalibraNonScores
NumberofcalibraNonexamples
Ambiguity
Cifar10
AmbiguityforjustnovelNethackimages
Confidentinsinglelabel
Open World ObservaCons
• InallbutonecasetherewaspracNcallynoabstenNon
• ThetheoryofconformalpredicNondoesnotaddresstheissueofopenworlds
• AppearsthatstandardconformalpredicNononitsownisnotsufficientforopenworlds
Next Steps for Open Worlds
Predictor ConformalPredicNon
AccuracyConstraint
Non-conformityScores
Newalgorithmsfortrainingpredictors.Goal:yieldreliableabstenNonfornovelclasses.
Next Step for Open Worlds
Predictor ConformalPredicNon
AnomalyDetector
normaldata
AnomalyHandler
anomalousdata
AccuracyConstraint
Non-conformityScores
Howtoselectanomalythreshold?Canweprovideanyguaranteesinopenworlds?