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Efficiency/Effectiveness Trade-offs in Learning to Rank Tutorial @ ICTIR 2017 http://learningtorank.isti.cnr.it/ Claudio Lucchese Ca’ Foscari University of Venice Venice, Italy Franco Maria Nardini HPC Lab, ISTI-CNR Pisa, Italy l a b o r a t o r y

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Page 1: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Efficiency/EffectivenessTrade-offsinLearningtoRank

Tutorial@ICTIR2017http://learningtorank.isti.cnr.it/

ClaudioLuccheseCa’Foscari UniversityofVenice

Venice,Italy

FrancoMariaNardiniHPCLab,ISTI-CNR

Pisa,Italy

l a b o r a t o r y

Page 2: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

TheRankingProblem

RankingisatthecoreofseveralIRTasks:

• DocumentRankinginWebSearch

• AdsRankinginWebAdvertising

• Querysuggestion&completion

• ProductRecommendation

• SongRecommendation

• …

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 2

Page 3: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

TheRankingProblem

Definition:Givenaqueryq andasetofobjects/documentsD,torankD soastomaximizeusers’satisfactionQ.

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 3[KDF+13]Kohavi,R.,Deng,A.,Frasca,B.,Walker,T.,Xu,Y.,&Pohlmann,N.(2013,August).Onlinecontrolledexperimentsatlargescale.In Proceedingsofthe19thACMSIGKDDinternationalconferenceonKnowledgediscoveryanddatamining (pp.1168-1176).ACM.

Goal#1:Effectiveness• MaximizeQ !

• buthowtomeasureQ?

Goal#2:Efficiency• Makesuretherankingprocessisfeasibleandnottooexpensive• InBing...“every100msecimprovesrevenueby0.6%.Everymillisecondcounts.”[KDF+13]

Page 4: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Agenda

1. IntroductiontoLearningtoRank(LtR)• Background,algorithms,sourcesofcostinLtR,multi-stageranking

2. DealingwiththeEfficiency/Effectivenesstrade-off• FeatureSelection,EnhancedLearning,Approximatescoring,FastScoring

3. Hands-onI• Software,dataandpubliclyavailabletools• TraversingRegressionForests,SoA toolsandanalysis

4. Hands-onII• Trainingmodels,Pruningstrategies,Efficientscoring

Attheendofthedayyou’llbeabletotrainahighqualityrankingmodel,andtoexploitSoAtoolsandtechniquestoreduceitscomputationalcostupto18x!

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 4

Page 5: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

DocumentRepresentationsandRanking

DocumentRepresentations

Adocumentisamulti-setofwords

Adocumentmayhavefields,itcanbesplitintozones,itcanbeenrichedwithexternaltextdata(e.g.,anchors)

Additionalinformationmaybeuseful,suchasIn-Links,Out-Links,PageRank,#clicks,sociallinks,etc.

HundredsignalsinpublicLtR Datasets

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 5

RankingFunctions

Term-weighting[SJ72]VectorSpaceModel[SB88]

BM25[JWR00],BM25f[RZT04]LanguageModeling[PC98]

LinearCombinationoffeatures[MC07]

Howtocombinehundredsofsignals?

[SJ72] Karen Sparck Jones. A statistical interpretation of term specificity and its application in retrieval. Journal of documentation, 28(1):11–21, 1972.[SB88]GerardSaltonandChristopherBuckley.Term-weightingapproachesinautomatictextretrieval.Informationprocessing&management,24(5):513–523,1988.[JWR00]KSparck Jones,SteveWalker,andStephenE.Robertson.Aprobabilisticmodelofinformationretrieval:developmentandcomparativeexperiments.Informationprocessing&management,36(6):809–840,2000[RZT04]StephenRobertson,HugoZaragoza,andMichaelTaylor.Simplebm25extensiontomultipleweightedfields.InProceedingsofthethirteenthACMinternationalconferenceonInformationandknowledgemanagement,pages42–49.ACM,2004.[PC98]JayMPonteandWBruceCroft.Alanguagemodelingapproachtoinformationretrieval.InProceedingsofthe21stannualinternationalACMSIGIRconferenceonResearchanddevelopmentininformationretrieval,pages275–281.ACM,1998.[MC07]DonaldMetzlerandWBruceCroft.Linearfeature-basedmodelsforinformationretrieval.InformationRetrieval,10(3):257–274,2007.

Page 6: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

RankingasaSupervisedLearningTask

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 6

d1

y1

Training Instance

Machine Learning Algo(NeuralNet, SVM, Decision-Tree)

q d2

y2

d3

y3

di

yi

LossFunction

RankingModel

Page 7: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Query/DocumentRepresentationUsefulsignals

• LinkAnalysis[H+00]• Termproximity[RS03]• Queryclassification[BSD10]• Queryintentmining[JLN16,LOP+13]• Findingentitiesdocuments[MW08]andinqueries[BOM15]

• Documentrecency [DZK+10]• Distributedrepresentationsofwordsandtheircompositionality[MSC+13]

• Convolutionalneuralnetworks[SHG+14]

• ….

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 7

• ExplicitFeedback• ThousandsofSearchQualityRaters

• Absolutevs.RelativeJudgments[CBCD08]

• ImplicitFeedback• clicks/querychains[JGP+05,Joa02,RJ05]• De-biasing/clickmodels[JSS17]

• Minimizeannotationcost• ActiveLearning[LCZ+10]• DeepversusShallowlabelling[YR09]

RelevanceLabelsGeneration

d

q y

Page 8: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

EvaluationMeasuresforRanking

Manyareintheform:

• (N)DCG[JK00]:• RBP[MZ08]:• ERR[CMZG09]:

DotheymatchUsersatisfaction?• ERRcorrelatesbetterwithusersatisfaction(clicksandeditorials)[CMZG09]

• ResultsInterleavingtocomparetworankings[CJRY12]• “majorrevisionsofthewebsearchrankers[Bing] ...Thedifferencesbetweentheserankersinvolvechangesofoverhalfapercentagepoint,inabsoluteterms,ofNDCG”

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 8

Gain(d) = 2

y � 1 Discount(r) =1

log(r + 1)

Q@k =X

ranks r=1...k

Gain(dr) · Discount(r)

Gain(d) = I(y) Discount(r) = (1� p)pr�1

Gain(d) = Ri

i�1Y

j=1

(1�Rj) with Ri = (2y � 1)/2ymax

Discount(r) = 1/r

[JK00]Kalervo Jarvelin andJaana Kekalainen.Ir evaluationmethodsforretrievinghighlyrelevantdocuments.InProceedingsofthe23rdannualinternationalACMSIGIRconferenceonResearchanddevelopmentininformationretrieval,pages41–48.ACM,2000.[MZ08]AlistairMoffatandJustinZobel.Rank-biasedprecisionformeasurementofretrievaleffectiveness.ACMTransactionsonInformationSystems(TOIS),27(1):2,2008.[CMZG09]OlivierChapelle,DonaldMetlzer,Ya Zhang,andPierreGrinspan.Expectedreciprocalrankforgradedrelevance.InProceedingsofthe18thACMconferenceonInformationandknowledgemanagement,pages621–630.ACM,2009.[CJRY12]OlivierChapelle,ThorstenJoachims,FilipRadlinski,andYisong Yue.Large-scalevalidationandanalysisofinterleavedsearchevaluation.ACMTransactionsonInformationSystems(TOIS),30(1):6,2012.

Page 9: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Isitaneasyordifficulttask?

Gradientdescentcannotbeapplieddirectly

Rank-basedmeasures(NDCG,ERR,MAP,…)dependondocumentssortedorder

• gradientiseither0(sortedorderdidnotchange)orundefined (discontinuity)

Solution:weneedaproxyLossfunction• itshouldbedifferentiable• andwithasimilarbehavioroftheoriginalcostfunction

di document score(model parameters)

ND

CG

@k

d0

d1

d2

d3

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 9

di document score(model parameters)

Pro

xy Q

ualit

y Fu

nctio

n

d0

d1

d2

d3

Page 10: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Point-WiseAlgorithms

di yi

Training InstanceEachdocumentisconsideredindependently fromtheothers

• Noinformationaboutothercandidatesforthesamequeryisusedattrainingtime

Adifferentcost-functionisoptimized• Severalapproaches:Regression,Multi-ClassClassification,Ordinalregression,… [Liu11]

AmongRegression-Based:GradientBoostingRegressionTrees [Fri01]

• MeanSquaredError isminimized

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 10[Liu11] Tie-Yan Liu. Learning to rank for information retrieval, 2011. Springer.[Fri01]JeromeHFriedman.Greedyfunctionapproximation:agradientboostingmachine.Annalsofstatistics,pages1189–1232,2001.

Training Algo: GBRTLoss Function: MSE

Page 11: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

GradientBoostingRegressionTrees

Iterativealgorithm:

Eachfi isregardedasastepinthebestoptimizationdirection,i.e.,asteepestdescentstep:

GivenL = MSE/2:

Gradientgi isapproximatedbyaRegressionTreeti

F (d) =X

i

fi(d)

fi(d) = �⇢i gi(d) � gi(d) = �@L(y, f(d))

@f(d)

f=P

j<i fj

�@⇥12MSE(y, f(d))

@f(d)= �

@⇥12

P(y � f(d))2

@f(d)= y � f(d)

WeakLearner

negativegradientbyline-search

pseudo-response

d

pre

dic

ted

doc

umen

t sco

re

f 1(d)

y

t1

y-f 1(

d)

f 2(d)

t2

f 3(d)

t3

ErrorY-F(d)

Page 12: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Pair-wiseAlgorithms:RankNet[BSR+05]DocumentsareconsideredinpairsEstimatedprobabilitythatdi isbetterthandj is:

LetQij bethetrueprobability,theCrossEntropyLoss is:

Weconsideronlypairswheredi isbetterthandj ,ie.,yi >yj :

Thisisdifferentiable: usedtotrainaNeuralNetworkwithback-propagation.

Otherapproaches:Ranking-SVM[Joa02],RankBoost[FISS03],…

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 12

[BSR+05]ChrisBurges,TalShaked,ErinRenshaw,AriLazier,MattDeeds,NicoleHamilton,andGregHullender.Learningtorankusinggradientdescent.InProceedingsofthe22ndinternationalconferenceonMachinelearning,pages89–96.ACM,2005.[Joa02]ThorstenJoachims.Optimizingsearchenginesusingclickthrough data.InProceedingsoftheeighthACMSIGKDDinternationalconferenceonKnowledgediscoveryanddatamining,pages133–142.ACM,2002.[FISS03]Yoav Freund,RajIyer,RobertESchapire,andYoram Singer.Anefficientboostingalgorithmforcombiningpreferences.Journalofmachinelearningresearch,4(Nov):933–969,2003.

di

Training Instance

Training Algo: ANNLoss: Cross Entropy

dj

with yi>yj

Pij

=eoij

1 + eoijoij = F(di)-F(dj)

Cij = �Qij logPij � (1�Qij) log(1� Pij)

Cij

= log(1 + e�oij)

Ifoij → +∞(i.e.,correctlyordered)

Cij → 0

Ifoij → -∞(i.e.,mis-ordered)

Cij → +∞

Page 13: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Pair-wiseAlgorithms

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 13[CQL+07]Zhe Cao,TaoQin,Tie-YanLiu,Ming-FengTsai,andHangLi.Learningtorank:frompairwiseapproachtolistwise approach.InProceedingsofthe24thinternationalconferenceonMachinelearning,pages129–136.ACM,2007.

RankNet performsbetter thanotherpairwisealgorithms

RankNet costisnotnicelycorrelatedwith

NDCGquality

Page 14: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

List-wiseAlgorithms:LambdaMart[Bur10]

Training Algo: GBRTLoss Function: MSE

di 𝜆i

Training Instance

q: …d1 d2 d3 dj d|q|

Recall:GBRTrequiresagradientgi foreverydi

First:estimatethegradientcomparingtodj,withyi>yj :

Then:estimatethegradientcomparingtoeveryotherdj forq

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 14[Bur10]ChristopherJ.C.Burges.Fromranknet tolambdarank tolambdamart:Anoverview.TechnicalReportMSR-TR-2010-82,June2010.

Δ Qualityafterswappingdi withdj

derivativeofthenegativeRankNet cost

Ifoij → +∞ (i.e.,correctlyordered)

𝜆ij → 0

Ifoij → -∞ (i.e.,mis-ordered)𝜆ij → |Δ NDCG|

gi = �i =X

yi>yj

�ij �X

yi<yj

�ij

�ij

=1

1 + eoij|�NDCG| = ��

ji

Topdocumentsaremorerelevant!

Page 15: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

List-wiseAlgorithms:someresults

• NDCG@10onpublicLtR Datasets

Otherapproaches:ListNet/ListMLE[CQL+07],ApproximateRank[QLL10],SVMAP[YFRJ07],RankGP[YLKY07],others...

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 15

Algorithm MSN10K Y!S1 Y!S2 Istella-SRankingSVM 0.4012 0.7238 0.7306 N/A

GBRT 0.4602 0.7555 0.7620 0.7313LambdaMART 0.4618 0.7529 0.7531 0.7537

[CQL+07]Zhe Cao,TaoQin,Tie-YanLiu,Ming-FengTsai,andHangLi.Learningtorank:frompairwiseapproachtolistwise approach.InProceedingsofthe24thinternationalconferenceonMachinelearning,pages129–136.ACM,2007.[QLL10]TaoQin,Tie-YanLiu,andHangLi.Ageneralapproximationframeworkfordirectoptimizationofinformationretrievalmeasures.Informationretrieval,13(4):375–397,2010.[YFRJ08]Yisong Yue,ThomasFinley,FilipRadlinski,andThorstenJoachims.Asupportvectormethodforoptimizingaverageprecision.InProceedingsofthe30thannualinternationalACMSIGIRconferenceonResearchanddevelopmentininformationretrieval,pages271– 278.ACM,2007.[YLKY07]Jen-YuanYeh,Jung-YiLin,Hao-RenKe,andWei-PangYang.Learningtorankforinformationretrievalusinggeneticprogramming.InProceedingsofSIGIR2007WorkshoponLearningtoRankforInformationRetrieval(LR4IR2007),2007.

Page 16: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

LearningtoRankAlgorithms• NewapproachestooptimizeIR

measures:• DirectRank[XLL+08],LambdaMart[Bur10],

BLMart[GCL11],SSLambdaMART[SY11],CoList[GY14],LogisticRank[YHT+16],…See[Liu11][TBH15].

• DeepLearning toimprovequery-documentmatching:• Conv.DNN[SM15],DSSM[HHG+13],

Dual-Embedding[MNCC16],LocalandDistributedrepr.[MDC17],WeakSupervision[DZS+17],NeuralClickModel[BMdRS16],…

• On-linelearning:• Multi-armedbandits[RKJ08],

Duelingbandits[YJ09],K-armedduelingbandits[YBKJ12],onlinelearning[HSWdR13][HWdR13],…

16[Liu11] Tie-Yan Liu. Learning to rank for information retrieval, 2011. Springer.[TBH15]Niek Tax,SanderBockting,andDjoerd Hiemstra.Across-benchmarkcomparisonof87learningtorankmethods.Informationprocessing&management,51(6):757–772,2015.

Figurefrom[Liu11]

Page 17: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

InthistutorialwefocusonGBRTs

AdsClickPrediction:GBDTasafeatureextractor,thenLogReg [HPJ+14]

AdsClickPrediction:refine/boostNN output[LDG+17]

ProductRanking:100GBDTswithpairwiseranking[SCP16]

DocumentRanking:GBDTnamedLogisticRank [YHT+16]

Ranking,forecasting&recommendations:ObliviousGBRT

17

[HPJ+14] XinranHe,JunfengPan,OuJin,TianbingXu,BoLiu,TaoXu,YanxinShi,AntoineAtallah,RalfHerbrich,StuartBowers,etal.Practicallessonsfrompredictingclicksonadsatfacebook.InProceedingsoftheEighthInternationalWorkshoponDataMiningforOnlineAdvertising,pages1–9.ACM,2014.[LDG+17] Xiaoliang Ling,Weiwei Deng, Chen Gu, Hucheng Zhou, Cui Li, and Feng Sun.Model ensemble for click prediction in bing search ads. In Proceedings of the 26th InternationalConferenceonWorldWideWebCompanion,pages689–698.InternationalWorldWideWebConferencesSteeringCommittee,2017.[SCP16]DariaSorokinaandErickCantu-Paz.Amazonsearch:The joyof rankingproducts. InProceedingsof the39th InternationalACMSIGIRconferenceonResearchandDevelopment inInformationRetrieval,pages459–460.ACM,2016.[YHT+16]DaweiYin,YueningHu,JiliangTang,TimDaly,MianweiZhou,HuaOuyang,JianhuiChen,ChangsungKang,HongboDeng,ChikashiNobata,etal.Rankingrelevanceinyahoosearch.InProceedingsofthe22ndACMSIGKDDInternationalConferenceonKnowledgeDiscoveryandDataMining,pages323–332.ACM,2016.

Page 18: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

InthistutorialwefocusonGBRTs

• Successful in several Data Challenges:• Winner of the Yahoo! LtR Challenge: combination of 12 ranking models,

8 of which were Lambda-MART models, each having up to 3,000 trees [CC11]• According to the 2015 statistics, GBRTs were adopted by the majority of the

winning solutions among the Kaggle competitions, even more than thepopular deep networks, and all the top-10 teams qualified in the KDDCup2015 used GBRT-based algorithms [CG16]

• New interesting open-source implementations:• XGBoost, LightGBM byMicrosoft, CatBoost by Yandex

• Pluggable within Apache Lucene/Solr18

[CC11] Olivier Chapelle and Yi Chang. Yahoo! learning to rank challenge overview. In Proceedings of the Learning to Rank Challenge, pages 1–24, 2011.[CG16] Tianqi Chen and Carlos Guestrin. Xgboost: A scalable tree boosting system. In Proceedings of the 22Nd ACM SIGKDD International Conference on Knowledge Discovery and Data Mining,KDD ’16, pages 785–794, New York, NY, USA, 2016. ACM.

Page 19: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Single-StageRanking

Requirestoapplythelearntmodel toeverymatchingdocument,andtogeneratetherequiredfeatures.Notfeasible!Wehaveatleast3 efficiencyvs.effectivenesstrade-offs.

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 19

ResultsRANKERQuery

Page 20: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Single-StageRanking

①FeatureComputationTrade-off• ComputationallyExpensive &highlydiscriminative featuresvs.computationallyCheap&slightlydiscriminative features

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 20

ResultsRANKERQuery

Page 21: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Two-StageRanking

Expensivefeaturesarecomputedonlyforthetop-K candidatedocuments passingthefirststage.HowtochoseK?②NumberofMatchingCandidatesTrade-off :• a Largeset ofcandidatesisExpensiveandproduceshigh-quality resultsvs.aSmallsetofcandidatesisCheap andproduceslow-quality results• 1000documents[DBC13] (Gov2,ClueWeb09-Bcollections)• 1500-2000documents[MSO13](ClueWeb09-B)• “hundredsofthousands”(over“hundredsofmachines”)[YHT+16a]

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 21

Query+top-K docs

STAGE1:

Matching/Recall-oriented

Ranking

STAGE2:

Precision-orientedRanking

Query Results

[DBC13]VanDang,MichaelBendersky,andWBruceCroft.Two-stagelearningtorankforinformationretrieval.InAdvancesinInformationRetrieval,pages423–434.Springer,2013.[MSO13]CraigMacdonald,Rodrygo LTSantos,andIadh Ounis.Thewhens andhows oflearningtorankforwebsearch.InformationRetrieval,16(5):584–628,2013.[YHT+16]Dawei Yin,Yuening Hu,Jiliang Tang,TimDaly,Mianwei Zhou,HuaOuyang,Jianhui Chen,Changsung Kang,Hongbo Deng,Chikashi Nobata,etal.Rankingrelevanceinyahoosearch.InProceedingsofthe22ndACMSIGKDDInternationalConferenceonKnowledgeDiscoveryandDataMining,pages323–332.ACM,2016.

Page 22: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Multi-StageRanking

• 3stages[YHT+16]:Contextualfeatures areconsideredinthe3rd stage• Contextual=>aboutthecurrentresultset• Rankbasedonspecificfeatures,Mean,Variance,Standardizedfeatures(seealso[LNO+15a]),

Topicmodelsimilarity• Firsttwostagesareexecutedateachservingnode

• N stages[CGBC17]:Whichmodel ineachstage?Whichfeatures?Howmanydocuments?• About200configurationstested• bestresultswithN=3stages,2500and700docsbetweenstages

• Apropermethodology/algorithmforchoosingthebestconfigurationisstillmissing.

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 22

STAGE1:

Matching/Recall-oriented

Ranking

STAGE2:

Precision-orientedRanking

Query Query+Top30

[YHT+16]Dawei Yin,Yuening Hu,Jiliang Tang,TimDaly,Mianwei Zhou,HuaOuyang,Jianhui Chen,Changsung Kang,Hongbo Deng,Chikashi Nobata,etal.Rankingrelevanceinyahoosearch.InProceedingsofthe22ndACMSIGKDDInternationalConferenceonKnowledgeDiscoveryandDataMining,pages323–332.ACM,2016.[CGBC17]Ruey-ChengChen,LukeGallagher,Roi Blanco,andJ.ShaneCulpepper.Efficientcost-awarecascaderankinginmulti-stageretrieval.InProceedingsofthe40thInternationalACMSIGIRConferenceonResearchandDevelopmentinInformationRetrieval,SIGIR’17,pages445–454,NewYork,NY,USA,2017.ACM.

STAGE3:

ContextualRanking

Results

Page 23: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

Multi-StageRanking

③ModelComplexityTrade-off :• Complex &Slow high-quality vs.Simple &Fast low-qualitymodels:

• Complex as:RandomForest,GBRT,InitializedGBRT,Lambda-MART,• Simple as:CoordinateAscent,RidgeRegression,SVM-Rank,RankBoost• In-between as:ObliviousLambda-Mart,ListNet

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 23

STAGEi-1:

CheapRanker

STAGEi:

AccurateRanker

Query

STAGEi+1:

VeryAccurateRanker

Results

Page 24: Efficiency/Effectiveness Trade-offs in Learning to Ranklearningtorank.isti.cnr.it/slides/Efficiency... · 2017-10-01 · The Ranking Problem Ranking is at the core of several IR Tasks:

ModelComplexityTrade-off

• Comparisononvaryingtrainingparameters[CLN+16]:• #trees,#leaves,learningrate,etc.

• Complexmodelsachievesignificantlyhigherquality• Bestmodeldependsontimebudget

• TodayisaboutModelComplexityTrade-off!

LuccheseC.,NardiniF.M.Efficiency/EffectivenessTrade-offsinLearningtoRank 24[CLN+16]GabrieleCapannini,ClaudioLucchese,FrancoMariaNardini,SalvatoreOrlando,RaffaelePerego,andNicolaTonellotto.Qualityversusefficiencyindocumentscoringwithlearning-to-rankmodels.InformationProcessing&Management,2016.

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Efficiency/Effectivenesstrade-offsin:• FeatureSelection• EnhancedLearningAlgorithms• Approximatescoring• FastScoring

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