News text generation with adversarial deep learning

80 Pages·2017·2.65 MB·English

MASTER’S THESIS | LUND UNIVERSITY 2017
News text generation with
adversarial deep learning
Filip Månsson, Fredrik Månsson
Department of Computer Science
Faculty of Engineering LTH
ISSN 1650-2884
LU-CS-EX 2017-18

News text generation with adversarial deep
learning
Filip Månsson Fredrik Månsson
[e-mail] [e-mail]
September 6, 2017
Master’s thesis work carried out at Sony Mobile Communications AB.
Supervisors: HåkanJonsson,[e-mail]
PierreNugues,[e-mail]
Examiner: JacekMalec,[e-mail]

Abstract
Inthisworkwecarryoutathoroughanalysisofapplyingaspecificfieldwithin
machinelearningcalled generativeadversarialnetworks,totheartofnatu-
rallanguagegeneration;morespecificallywegeneratenewstextarticlesinan
automatedfashion. Todothis,weexperimentedwithafewdifferentarchitec-
turesandrepresentationsoftext,evaluatedtheresultsandusedtheinformation
retrieved from the results, to create a model that should give the best result.
For evaluation, we used perplexity and human evaluation. We also looked at
thetokendistributiontoseewhichmodelcapturesthetextsmostsuccessfully.
We show that it is possible to use generative adversarial networks to gen-
eratesequencesoftokensthatresemblenaturallanguage,butthisdoesnotyet
reach the quality of human-written text. Further hyperparameter tuning and
usinganarrower-subjectedcorpuscouldimprovetheoutput.
Keywords: Machine learning, generative adversarial learning, GAN, natural lan-
guagegeneration
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Acknowledgements
Wewouldliketothankbothofoursupervisorsforhelpinguswiththisprojectandtaking
thetimeandefforttoanswerourquestionsaswellasprovidinguswithvaluablefeedback.
We also want to send our regards to our parents and siblings for their support throughout
ourlives.
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Contents
1 Introduction 7
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2 ProblemDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3 RelatedWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Background 11
2.1 TextGeneration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 NeuralNetworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.1 Convolutionalneuralnetworks . . . . . . . . . . . . . . . . . . . 12
2.2.2 Recurrentneuralnetworks . . . . . . . . . . . . . . . . . . . . . 12
2.2.3 Longshorttermmemory . . . . . . . . . . . . . . . . . . . . . . 13
2.2.4 Residuallearning . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 GenerativeAdversarialNetworks . . . . . . . . . . . . . . . . . . . . . . 13
2.3.1 Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.2 Discriminator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.3 Costfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.4 Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.5 Knownissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 Wasserstein-GAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4.1 Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.2 Critic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.3 Costfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.4 Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.4.5 Knownissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5 ImprovedWasserstein-GAN . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5.1 Costfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5.2 Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.5.3 Knownissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.6 TextRepresentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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CONTENTS
3 Approach 23
3.1 OverallApproach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.1 Corpus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.2 Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.1 Baseline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.2 GANmodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.3 WGANmodels . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.4 Motivationofapproach . . . . . . . . . . . . . . . . . . . . . . . 29
4 Evaluation 31
4.1 MetricsUsed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.1.1 Perplexity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.1.2 Humanevaluation . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.1 Resultsusingcharacters . . . . . . . . . . . . . . . . . . . . . . 33
4.2.2 Resultsusingwords . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.2.3 Generatedtext . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.3 FinalModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.4 HumanEvaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5 Conclusions 55
5.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.2 FutureWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
AppendixA Generatedarticles 63
AppendixB Questionnaire 65
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